JPH1084332A - Communication system and wavelength control method used therein - Google Patents

Abstract

[PROBLEMS] To control wavelengths emitted from a plurality of communication nodes, multiplex high-density wavelengths, and avoid interference with emission wavelengths of other communication nodes. A wavelength division multiplex communication system and a control communication system used for communication control of the wavelength multiplex communication system are provided. Each communication node detects a wavelength in an optical fiber and maintains a predetermined wavelength interval. The wavelength division multiplexing communication system controls the emission wavelength of the LD of its own station by transmitting a control signal by packet communication. The control communication system is configured as a wavelength control node in parallel with the communication node, as a non-receiving communication node among the communication nodes, as a plurality of wavelength control nodes, and as a center node with a star coupler as a center communication node. , Each communication node can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength control method for controlling a plurality of transmission wavelengths used in a wavelength division multiplexing communication system, and an optical node which executes the wavelength control method and is controlled.
The present invention relates to a communication system including a center node and a wavelength control node.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for a society in which a large amount of information can be transmitted to anyone at any time and at any time. Therefore, an optical communication system having a high possibility of transmitting a large amount of information at high speed is expected. The gigabit rate has become reality by multiplexing a large number of wavelengths using an optical fiber, and the terabit rate is encountered when it is not a dream. The present invention also has a more effective configuration in accordance with such an era.

[0003] Wavelength division multiplexing communication (W
DM: Wavelength Division Multiplexing is an optical frequency division multiplexing (optical FDM).
It is also referred to as “ultiplexing”, and one transmission line can have a number of independent channels (transmission wavelengths) for different wavelengths. Unlike time division multiplexing (TDM), multiplexing on the time axis such as frame synchronization is not required. Therefore, it is not necessary to match the transmission speed of each channel, and it is also suitable for multimedia communication that requires network flexibility. ing.

As an example of a wavelength division multiplex communication system, there is a system having a passive star type configuration and having, within one transmission line, signals of a wavelength division multiplex communication system and a communication system for control independent thereof. In this wavelength division multiplexing communication system, a wavelength division multiplexing communication system is used for transmission one-to-one reception and transmission one-to-multiple reception line communication. On the other hand, independent communication lines
FIG. 20 shows a configuration example of a wavelength multiplex communication system used for control communication and packet communication of a wavelength multiplex communication system (hereinafter, referred to as a packet communication system). In the figure, terminal stations 612 to 61n are communication nodes 32.
2-32n, optical fibers 341-34n, 351-35
n to the star coupler 33 to form a network. The optical signals transmitted from the communication nodes 322 to 32n are transmitted to all the communication nodes 322 by the star coupler 33.
~ 32n (including myself).

Optical fibers 341 to 34n and 351 to 35, which are transmission lines in such a wavelength division multiplex communication system, are used.
FIG. 6 shows the wavelength allocation of the optical signal transmitted on n. The wavelength division multiplexing communication system is in the 1.5 μm band of the low loss area
A 1.3 μm band is allocated to the packet communication system for wavelength control. The wavelength division multiplexing communication system has m (m ≦ n: the number of channels is smaller than the number of communication nodes) independent wavelength channels, and each communication node occupies the channel as needed, and performs communication between each communication node. Do. Packet communication system is F
A protocol such as DDI (Fiber Distributed Data Interface) is commonly used by all communication nodes.

In order to increase the number of channels in a wavelength division multiplexing communication system, the wavelength interval between channels (hereinafter, referred to as a channel interval) is on the order of 10 GHz (for example, about 0.08 nm when the wavelength is converted in the 1.55 μm band). In this case, it is necessary to control so as to maintain the transmission wavelength of each communication node.
Several methods have been proposed as methods for keeping the channel spacing of the transmission wavelength from the distributed communication nodes constant (for example, the publication Electronics Letters, Vol. 23 (1987), No. 23, 1243). ~ 1245,
“Frequency Stabilization of FDM Optical Signals O
riginating from different locations ”).

[0007] Among them, the so-called F in Japanese Patent Application No. 6-296660, filed by the present inventors, is proposed.
In the CS (Floating Channel Stack) method, the initial setting and resetting of the wavelength are easy, and the control of the transmitter of the communication node does not require a wavelength detection circuit, and the control is simple.

In the FCS system, each communication node detects the channel interval between its own wavelength and the wavelength of the channel adjacent to the longer wavelength side in the wavelength arrangement, and determines the wavelength of its own station so that the channel interval becomes constant. Control. FIG. 21 shows an example of the operation. When the self-station communication node starts to emit light, it starts far from the light-emission, for example, ch1 to ch4 of the other-station communication node, and starts from the shorter wavelength side of the wavelength range of the wavelength division multiplex communication system, for example, the wavelength indicated by ch5 (see FIG. 21a) The wavelength is gradually shifted to the longer wavelength side, and a predetermined c is shifted from the adjacent wavelength ch4 on the longer wavelength side.
When the interval becomes h, the transmission wavelength of the own station is output to the optical transmission line, the communication signal is output to the desired partner station, and the steady state is maintained (FIG. 21B). When a certain communication node of another station ends transmission and stops emitting light (ch3 in FIG. 21C), the communication nodes (ch4, ch) that emit light on the shorter wavelength side
5) gradually shifts the emission wavelength to the longer wavelength side, stops the wavelength shift when the transmission wavelength on the longer wavelength side becomes a predetermined channel interval, and maintains the transmission at the emission wavelength (FIG. 21d). As a result, in the steady state, the transmission wavelengths of each communication node are arranged at equal ch intervals from the long wavelength end of the wavelength range of the wavelength division multiplex communication system (FIGS. 21B and 21D). The above operation is because each communication node has a mechanism that detects the emission wavelength of its own station and the adjacent wavelength on the long wavelength side and operates so that the channel interval is maintained within a predetermined range. is there.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel configuration for controlling a wavelength channel interval in a wavelength division multiplexing communication system, and particularly to configure a network system at low cost. .

[0010]

A communication system for achieving the above object of the present invention comprises a first communication system for performing wavelength division multiplexing communication and a second communication system for performing communication independent of the first communication system.
And a plurality of communication nodes that perform communication via at least the first communication system, and a wavelength control unit in the communication system detects a wavelength arrangement in the first communication system. Transmitting a wavelength control signal based on the detected wavelength allocation to the plurality of communication nodes via the second communication system, and controlling the transmission wavelength based on the wavelength control signal in the plurality of communication nodes. It is characterized by.

With this configuration, since the wavelength of the light output from each communication node to the first communication system is controlled by the wavelength control unit, no interference occurs. In addition, each communication node does not need to detect the wavelength arrangement and control the wavelength of the output light of its own node, and each communication node needs to have a system for detecting the wavelength arrangement separately from the system that receives the wavelength multiplexed signal. Disappears.

The wavelength control unit can be provided at various positions in the communication system.
A configuration may be adopted in which the wavelength control node is provided separately from the plurality of nodes.

Further, a configuration in which a plurality of the wavelength control nodes are provided can be adopted. At this time, even if one wavelength control node fails, the wavelength control can be performed by another wavelength control node, so that the reliability of the communication system can be improved. As a configuration for switching the wavelength control node that transmits the wavelength control signal, the transmission of the wavelength control signal is performed by the first wavelength control node, and the first wavelength control node stops transmitting the wavelength control signal. Sometimes the second
Of the wavelength control nodes may transmit the wavelength control signal. The second wavelength control node monitors a wavelength control signal sent by the second communication system, and sends a wavelength control signal when a wavelength control signal does not come for a predetermined time or more. Good.

The first and second wavelength control nodes may alternately send out wavelength control signals. This configuration is preferable because the load on the wavelength control node can be distributed. At that time, if one of the wavelength control nodes stops sending the wavelength control signal, the interval at which the wavelength control signal is sent becomes long. At that time, the remaining wavelength control node sends the wavelength control signal. By shortening the interval, accurate wavelength control can be performed even when one wavelength control node does not function.

In a configuration using a plurality of wavelength control nodes, whether or not the other wavelength control node is functioning can also be known by detecting the wavelength arrangement of the first communication system. That is, if the wavelength control node does not send out the wavelength control signal and detects a control failure of the wavelength allocation in the first communication system, there is a possibility that the other wavelength control nodes are not functioning properly. The own wavelength control node may transmit the wavelength control signal. According to this configuration, since the wavelength control node does not need to monitor the wavelength control signal transmitted by another wavelength control node, the receiving function of the second communication system can be omitted and the configuration can be simplified.

Further, a communication node which does not receive a signal via the first communication system among the plurality of communication nodes without providing a wavelength control node as a wavelength control unit may be provided. In this configuration, there is no need to provide a wavelength control node, and the configuration can be simplified. In particular, among the communication nodes that have not received the signal via the first communication system, the communication nodes may receive the signal immediately before receiving the signal via the first communication system or the signal via the first communication system. If the communication node in the state immediately after the reception has been configured to be the wavelength control unit, the above-mentioned state is controlled when the wavelengths of the channels used in the first communication system are controlled to be arranged at predetermined wavelength intervals. Means that the state of being arranged at a predetermined wavelength interval is in a disturbed state, and the communication node that caused this becomes the wavelength control unit. At this time, the wavelength when the communication node in the state immediately before receiving the signal via the first communication system or immediately after receiving the signal via the first communication system transmits the wavelength control signal is transmitted. The transmission interval of the control signal is a state other than a state immediately before receiving the signal via the first communication system or a state immediately after receiving the signal via the first communication system, and If the communication node that is not receiving a signal via the first communication system transmits the wavelength control signal and the wavelength is shorter than the transmission interval of the wavelength control signal, the predetermined wavelength interval becomes as described above. This is preferable because the disordered state can be quickly eliminated.

Further, the communication node serving as the wavelength control unit is changed when the communication node that has not received the signal via the first communication system receives the wavelength control signal for a predetermined time after receiving one of the wavelength control signals. When the wavelength control signal is not received, the wavelength control unit can be used as the wavelength control unit. At this time, if the length of the predetermined time is changed depending on the state of the communication node, the priority can be given to the communication node that becomes the wavelength control unit.
In other words, a communication node desirably forming a wavelength controller may set the predetermined time short.

The communication node serving as the wavelength control unit can be replaced by designating the communication node serving as the wavelength control unit by the communication node serving as the wavelength control unit.

Further, the communication system may be configured such that each communication node is connected to a center node, and a wavelength controller may be provided in the center node. At this time, in the center node, if a signal sent from each of the plurality of communication nodes via the first communication system is not distributed to another communication node until a predetermined wavelength is reached, control becomes impossible. When the runaway wavelength goes out of control, when transmission starts, or when the wavelength is moved beyond the wavelength used by another communication node, the first communication system should not be affected. It is preferable.

Further, when the wavelength control signal includes the wavelength control information of all the channels used in the first communication system, all the communication nodes can identify the wavelength arrangement state almost simultaneously by one wavelength control signal. It is suitable.

The wavelength control signal includes, as information for controlling the wavelength of each channel, information indicating that the wavelength of each channel is “maintained”, “move to a longer wavelength”, or “move to a shorter wavelength”. It can take a configuration that includes it.

Further, the wavelength control signal may be configured to include information indicating a channel not used in the first communication system, and at this time, the communication node converts the information indicating the unused channel into information indicating the unused channel. The channel to be used can be determined based on this.

Further, it is possible to assign a channel to be used in the first communication system by demand assignment control using the second communication system.

As described above, if the wavelengths used in the first communication system are arranged at predetermined wavelength intervals, the wavelength range can be used at a high density, which is preferable.

Further, various configurations such as a configuration in which the first communication system and the second communication system are wavelength-division multiplexed and a configuration in which separate transmission lines are used can be adopted. First communication system and second communication system
When the communication systems are multiplexed, the wiring can be simplified and the combination and arrangement of the wiring can be easily performed. At that time, the communication node may include means for separating the multiplexed first communication system and second communication system.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] In the first embodiment, the entire wavelength allocation of the wavelength multiplex communication system (first communication system) is detected by the wavelength control node installed in the network, and the wavelength multiplex communication system is used. Control information for maintaining a constant wavelength interval between adjacent channels is notified to each communication node in the network by a packet communication system (second communication system) independent of the wavelength multiplex communication system. Based on this control information, each communication node controls the wavelength of the light source of the transmitter of the wavelength division multiplex communication system of its own station so that the wavelength interval between adjacent channels is constant.

In this embodiment, the independent communication system is a packet communication system, and control information is broadcast as wavelength control packets from the wavelength control node to all communication nodes in the network. Further, the wavelength control node has only a transmission function of the packet communication system, and transmits a wavelength control packet at regular time intervals.

Hereinafter, a detailed description will be given with reference to the drawings. FIG.
1 is a configuration diagram of a wavelength division multiplexing communication system to which the wavelength control method of the present embodiment is applied, and is a passive star type wavelength division multiplexing communication system having n terminal stations. The present embodiment is characterized in that it has a wavelength control node 36 and optical fibers 37 and 38 for connecting the wavelength control node 36 and the star coupler 33 thereto. The terminal stations 311 to 31n communicate with each other via communication nodes 321 to 32n using transmission signals and reception signals. Communication node 3
21 to 32n convert the electric signals from the terminal stations 311 to 31n into optical signals, output the optical signals to the optical fibers 341 to 34n, and convert the optical signals input from the optical fibers 351 to 35n into electric signals. The star coupler 33 includes optical fibers 341 to
34n and the optical signal input from the optical fiber 37 are distributed to the optical fibers 351 to 35n and the optical fiber 38.

FIG. 2 shows an example of the operation of the wavelength control method of the present embodiment. In FIG. 2, the wavelength arrangement before the control operation, the wavelength control packet sent in that state, and the control operation are shown in three cases, ie, at the start of light emission (a), correction of deviation (b), and elimination of empty space (c). The latter wavelength arrangement is shown.
In the wavelength arrangement diagram shown in FIG. 2, the solid line indicates the wavelength of the communication node that has already emitted light, and the dotted line indicates the target wavelength for wavelength control. The detailed operation will be described later.

FIG. 3 is a diagram showing a data format of a wavelength control packet transmitted by a packet communication system in order to control the wavelength of a communication node in the system by the wavelength control node in the present embodiment. A 2-bit wavelength control code is assigned to one channel. The 2-bit wavelength control code has a maximum number of channels (m) and a data length of m.
× 2 bits. For each channel, "00" indicates that the channel is not used, "01" indicates that the wavelength is shifted to the longer wavelength side, "10" indicates that the wavelength is shifted to the shorter wavelength side, and "11" indicates that the current state is maintained.

FIG. 4 is a configuration diagram of the wavelength control node 36. The wavelength control node 36 includes a wavelength control system 41, a wavelength variable filter 42, a wavelength variable filter driving circuit 43, a light receiving element 44, an amplifier 45, a discriminator 46, an LD 47, and an LD driving circuit 48.

The wavelength control system 41 comprises an arithmetic processing circuit, a storage element, a D / A converter, and the like. In response to a control signal from the wavelength control system 41, a peak wavelength (hereinafter simply referred to as a wavelength) of a transmission spectrum of the wavelength variable filter 42 is swept through the wavelength variable filter driving circuit 43, and the light receiving element 4
4, the signal is converted into an electric signal by the amplifier 45, the wavelength arrangement of the wavelength multiplex communication system is detected based on the output signal of the discriminator 46, and the wavelength control packet is transmitted by the packet communication system.
The LD 47 is driven through the D drive circuit 48, and the wavelength of each communication node is controlled through the optical fiber 37.

The wavelength tunable filter 42 is for detecting the wavelength arrangement of the wavelength division multiplex communication system. In this embodiment, the wavelength band of the wavelength division multiplex communication system is exemplified as a 1.5 μm band. The half-width of the transmission spectrum of the wavelength tunable filter 42 is desirably about 1/5 to 1/10 of the channel interval (for example, channel interval: 5 GHz (0.0 in the 1.5 μm band).
1 GHz). Currently practicable wavelength tunable filter elements include, for example, conference proceedings ECOC
(Europian Conference on Optical Communication) '9
0-605, “A field-worthy, high-performance, tunable
There is a fiber Fabry-Perot filter described in “Fiber Fabry-Perot filter.” This element is an FSR (Free Spe
Each ctral range has a transmission spectrum peak,
By setting the FSR to be equal to or larger than the wavelength variable range of the wavelength division multiplex communication system, it functions as an optical bandpass filter. The filtering wavelength can be varied by a driving voltage from the wavelength variable filter driving circuit 43.

The wavelength variable filter driving circuit 43 is a voltage control type voltage source, and amplifies the control signal from the wavelength control system 41 by voltage. The light receiving element 44 converts the transmitted light from the wavelength tunable filter 42 into an electric signal, the amplifier 45 amplifies the electric signal, and the discriminator 46 compares the electric signal with a threshold value. Is '1', if less than '0'
Is output to the wavelength control system 41. The wavelength control system 41 compares the digital output of the discriminator 46 with the control voltage supplied to the wavelength tunable filter driving circuit 43 to determine the wavelength channel existing on the light receiving optical fiber and the predetermined channel.
Judgment is made as to whether the interval is a predetermined channel interval. If the interval is a predetermined channel interval, the wavelength is maintained for each channel. In other cases, a control signal such as shifting to a longer wavelength side, shifting to a shorter wavelength side, or no channel wavelength is output. .

The LD 47 is a light source of a packet communication system.
In the present embodiment, the wavelength is used in the 1.3 μm band, but another wavelength band may be used. The LD drive circuit 48 is an LD4
7 is a current source that modulates 7 with a communication control signal from the wavelength control system 41. In the present embodiment, since high-density wavelength multiplexing is not performed in the packet communication system, an example is shown in which the LD 47 is directly intensity-modulated, but another modulation method may be used.

FIG. 5 is a configuration diagram of the communication nodes 321 to 32n. It has two functions of a wavelength multiplex communication system and a packet communication system. The wavelength division multiplexing communication system includes a wavelength control system 51, a wavelength variable LD 52, a wavelength variable LD drive circuit 54, an optical modulator 5
6. It is composed of an optical modulator driving circuit 57, a wavelength variable filter 53, a wavelength variable filter driving circuit 55, a light receiving element 58, and a receiving circuit 59. The packet communication system includes an LD 47, an LD driving circuit 48, a light receiving element 510, and a receiving circuit 511. The transmission unit and the reception unit of the two communication systems are connected by an optical multiplexer 512 and an optical demultiplexer 513, respectively.

Here, the wavelength control system 51 includes a receiving circuit 511.
Tunable LD based on the contents of the wavelength control packet from
The wavelength variable LD 52 is controlled via the drive circuit 54. Further, the wavelength control system 51 controls the transmission wavelength of the wavelength tunable filter 53 via the wavelength tunable filter driving circuit 55, and changes the wavelength of the wavelength tunable filter 53 from the channel of the wavelength multiplex communication system to the wavelength of the channel addressed to the own station. Match and maintain.

The wavelength tunable LD 52 is a light source for transmission in a wavelength division multiplex communication system, and its wavelength is, for example, in the 1.5 μm band. Research is currently underway to increase the wavelength tunable range, but at the current practical level, a multi-electrode DBR
(Distributed Bragg Reflector) type and DFB (Distrib
uted Feedback) type, and the wavelength variable width is several nm.
It is. For example, IEICE Technical Report OQ
E (Optical and Quantum Electronics) 89-116, "Three-electrode long resonator λ / 4 shift MQWDFB laser".

Further, the wavelength tunable filter 53 is a wavelength tunable filter for reception in a wavelength division multiplex communication system, and its wavelength is, for example, 1.5 μm similarly to the emission wavelength of the wavelength tunable LD 52.
A belt is used. Further, it is the same element as the wavelength tunable filter 42 of FIG. 4, but it is desirable that the half width of the transmission spectrum is about 1/3 to 1/6 of the channel interval (for example, 1.5 GHz at the channel interval of 5 GHz).

The wavelength variable LD drive circuit 54 is a voltage control type current source, and drives (injects current) the wavelength variable LD 52 so as to have a wavelength corresponding to a control signal from the wavelength control system 51. The three-electrode long resonator λ / 4 shift M
When the QWDFB laser is used, the output of the wavelength variable LD driving circuit 54 becomes three.

The wavelength tunable filter driving circuit 55 is a voltage control type voltage source. A wavelength control signal and a lock ON / OFF signal are input from the wavelength control system 51. When the receiving channel is selected (lock OFF), the wavelength tunable filter 5 is set to a wavelength corresponding to the control signal from the wavelength control system 51.
3 is driven to lock the wavelength of the tunable filter 53 to the wavelength of the receiving channel during reception (lock ON).

Further, the optical modulator 56 and the optical modulator driving circuit 57 are for modulating the intensity of the output light of the wavelength tunable LD 52 with the transmission signal of the wavelength multiplex communication system input from the terminal station. When directly modulating with a current injected into the wavelength tunable LD 52, a wavelength fluctuation of about 0.1 nm occurs. Therefore, an external intensity modulation method using the optical modulator 56 is preferably used. May be used.

The light receiving element 58 and the receiving circuit 59
Is for receiving a reception signal addressed to its own station in the wavelength division multiplex communication system. The optical signal of the channel selected by the wavelength variable filter 53 is converted into an electric signal, and the electric signal as a digital signal is reproduced. The reproduced received signal is output to the terminal station and subjected to signal processing.

The LD 47 and the LD drive circuit 48 of the packet communication system convert the packet signal into an optical signal as in the case of FIG. 4, and for example, an optical multiplexer 512 with a wavelength of 1.3 μm.
And output to the optical fiber. The signal is received by the light receiving element 510 and the receiving circuit 511 in the same manner as the other communication nodes, and the signal of the packet communication system is received. The control signal transmitted in the packet format is detected and transmitted to the wavelength control channel 51.

The optical multiplexer 512 is, for example, 1.5 μm
The optical signal of the band wavelength multiplex communication system and the optical signal of the 1.3 μm band packet communication system are multiplexed and output to an optical fiber. On the other hand, the optical demultiplexer 513 separates the optical signal input from the optical fiber in the wavelength band, inputs the 1.5 μm band optical signal to the wavelength tunable optical filter 53, and converts the 1.3 μm band optical signal into the light receiving element 510. To enter.

FIG. 6 is a wavelength allocation diagram showing the wavelength allocation in this embodiment. The packet communication system uses the 1.3 μm band,
The wavelength multiplex communication system uses the 1.5 μm band. Since the packet communication system does not perform high-density wavelength multiplexing, wavelength control of the light source is not performed, and the wavelength width of the channel is wide. On the other hand, the wavelength division multiplex communication system has a high density (ch interval: 10 GHz (0.08 n
In order to perform wavelength multiplexing (m) and below) (maximum m channels), the wavelength of the light source of each communication node is controlled so that the channel spacing can be maintained, and the wavelength width of each channel is narrowed.

The wavelength control node shown in FIG. 4 repeatedly performs a series of operations of detecting the wavelength arrangement in the optical fiber, calculating the shift direction of each channel, and transmitting the wavelength control packet, thereby changing the transmission wavelength of each communication node. Control.

The detection of the wavelength arrangement by the wavelength control node is performed by sweeping the transmission wavelength of the wavelength tunable filter 42 over the entire wavelength range of the wavelength division multiplex communication system.
The sweeping step is set to be smaller than the half-width of the transmission spectrum of the wavelength tunable filter 42 in order to always detect the wavelength at which each communication node emits light (for example, if the half-width of the transmission spectrum is 1 GHz, the step is 0.3. 25GH
z). In this case, the output of the discriminator 46 becomes “1” in a plurality of successive steps for one channel wavelength.
The wavelength control system 41 regards the center step as a wavelength position. Since the wavelength control system 41 controls the sweep of the tunable filter 42 by voltage, the positional relationship of each wavelength is converted from the control voltage to the tunable filter driving circuit 43. Note that the voltage wavelength characteristic of the wavelength tunable filter 42 has nonlinearity. This characteristic is stored in the wavelength control system 41 in advance, and the wavelength arrangement can be correctly detected from the control voltage.

The shift direction of the transmission wavelength of each light emitting communication node is determined as follows. The wavelength closest to the long wavelength is defined as ch1, and thereafter, ch2 and ch are shifted to the short wavelength side.
3 is assumed. The shift direction of ch2 is determined so that it is closer to the short wavelength by a predetermined ch interval from ch1. c
The shift direction of h3 is determined so that it is closer to the short wavelength by twice the ch interval from ch1. Similarly, ch
The shift direction is determined so that m is closer to the short wavelength by (m-1) times the ch interval than ch1.

The shift amount in one step of the wavelength tunable LD 52 shown in FIG. 5 is made smaller than the half width of the transmission spectrum of the wavelength tunable filter 53 for reception in the wavelength division multiplex communication system (for example, the half width of the transmission spectrum 1.5 GHz). The shift amount is 0.5 GHz.

Next, the assignment of channels to communication nodes is performed as follows. The wavelength control code '0' is transmitted in the wavelength control packet transmitted before the start of the light emission at the transmission wavelength.
The lowest numbered channel with data of 0 'is assigned to that communication node. Thereafter, this communication node controls the wavelength by the wavelength control code of this channel until the following two states are reached.

(1) A state in which communication ends and emission stops.

(2) A state in which the wavelength control code of a channel whose number is smaller than that of its own channel is "00".

In the state of (2), a channel with a smaller number is assigned, and thereafter, the channel follows the wavelength control code of this channel.

A specific example of the operation of the above wavelength control method will be described with reference to FIG.

(A) At the time of starting light emission It is assumed that the wavelength arrangement of the wavelength division multiplexing communication system before the start of light emission has a wavelength arrangement of ch1 to ch4 as shown at the top. The wavelength arrangement of the packet communication system is omitted. Already 4
Channel is used, and a predetermined channel is set based on ch1.
The wavelength arrangement is maintained at intervals (the solid line and the dotted line match). The wavelength control code of the wavelength control packet in this wavelength arrangement is "11" for ch1 to ch4 and "00" for ch5 and thereafter. Since the wavelength control code is “00” and the channel with the smallest number is ch5, the channel of the communication node that starts emitting light is ch5 and starts emitting light from the shorter wavelength side. The wavelength arrangement after the start of light emission is c as shown in the middle row.
Only h5 is shifted (solid and dotted lines are shifted). The wavelength control code in this wavelength arrangement is '1' for ch1 to ch4.
1 ', ch5 becomes'01', and ch6 and thereafter become '00'. After receiving the wavelength control packet, the communication node of ch5 shifts the wavelength to the longer wavelength side. The wavelength control code of ch5 remains '01' until the solid line and the dotted line match in the wavelength arrangement diagram, and the communication node of ch5 shifts the wavelength to the longer wavelength side each time a wavelength control packet is received. In this way, interference at the start of light emission can be prevented, and it is possible to quickly move to a certain wavelength interval with an adjacent channel. (B) Correction of deviation In the upper part of FIG. 2B, five channels are used, and
ch2 and c from the wavelength arrangement for each ch interval based on h1
This shows how h4 is shifted. ch2 is on the short wavelength side, c
h4 is shifted to the longer wavelength side. In the wavelength control code in this wavelength arrangement, ch1, ch3, and ch5 are '11', ch
6 and later are '00', ch2 is '01', ch4 is '1'
It becomes 0 '. After receiving the wavelength control packet, the communication node using ch2 shifts the wavelength to the longer wavelength side. After receiving the wavelength control packet, the communication node using ch4 shifts the wavelength to the shorter wavelength side.
As a result, as shown in the lower part of FIG. (C) Elimination of Empty Space The upper part of FIG. 2 (c) shows a state in which the communication node that has used ch2 among the five used channels terminates communication and stops emitting light. ch1 and c
An empty space (space larger than twice the ch interval) is formed between h3. After this state, the wavelength control code of the first wavelength control packet is ch1, ch3, ch4, c
h5 is '11', and ch2 and ch6 and thereafter are '00'. The communication nodes that have used ch3 and subsequent channels that have received the wavelength control packet recognize that ch2 has become "unused", and reduce the channel numbers assigned to themselves by one. In the wavelength control code of the wavelength control packet transmitted next, ch1 is “11”, ch2 to ch
4 is '01', and ch5 and later are '00'. ch2
After receiving the wavelength control packet, the communication node using ch4 shifts the wavelength to the longer wavelength side. ch2
The wavelength control codes of ch2 to ch4 remain '01' until the solid line and the dotted line of each channel match in the wavelength arrangement diagram.
The communication node using .about.ch4 shifts the wavelength to the longer wavelength side each time a wavelength control packet is received. ch
When each of the communication nodes 2 to 4 has a desired transmission wavelength, the wavelength arrangement is the same as that in FIG.

In the present embodiment, the wavelength control node
As shown in (1), there is no need to have a receiving function of the packet communication system, and the configuration is simplified. In addition, each communication node does not require a wavelength tunable filter and a discriminator for detecting a wavelength arrangement state, and has a simple configuration, so that a multi-wavelength communication system can be configured at low cost overall.

[Second Embodiment] In the present embodiment, the wavelength control node has a receiving function of a packet communication system, and transmits a wavelength control packet as required, not at every predetermined timing. There are features. The configuration diagram of the entire system is the same as that of FIG.

FIG. 7 is a configuration diagram of the wavelength control node in the present embodiment. The difference from the first embodiment (FIG. 4) is that a receiving function of a packet communication system is provided. The receiving function of the packet communication system includes a light receiving element 510, a receiving circuit 511, and an optical demultiplexer 513. The functions of these components are the same as those used in each communication node in FIG.

In the present embodiment, the wavelength control node does not send out the wavelength control packet at regular time intervals, but performs the following three steps.
Only in the case of the above, the wavelength control packet is transmitted.

(1) When there is a communication node that starts light emission, (2) When there is a shift in wavelength arrangement, and (3) When an empty space is created.

The detection of the wavelength arrangement is performed at fixed time intervals shorter than the packet transmission time interval, and is also performed after a light emission start request is issued from a communication node in the packet communication system. The use of the channel is performed by demand assignment by a packet communication system. Other configurations and operations are the same as those of the first embodiment.

When each communication node intends to perform communication transmission from its own end station to the other end station, it first emits a code whose emission is scheduled to start via a transmission path of the packet communication system during non-transmission of the packet communication system. Send. Also, when the communication that has been transmitting and emitting light is stopped and used, a code to that effect is transmitted to the packet communication system by emitting light. The wavelength control node is an optical multiplexer 513
The optical signal in the 1.3 μm band of the packet communication system is converted into an electric signal by the light receiving element 510 via a communication circuit, and a code transmitted from each communication node is received and decoded by a receiving circuit.
Transmit to 1. Further, when there is a deviation in the wavelength arrangement or when a wavelength stop is detected, the wavelength control system 71 detects that from the discriminator 46 and responds to each of the above (1) to (3). The wavelength control code is transmitted to the optical fiber by the packet communication system. Each communication node controls the wavelength allocation of the WDM communication system according to the wavelength control code.

In the present embodiment, it is not necessary to transmit the wavelength control packet at regular intervals, so that the traffic of the packet communication system can be effectively used for other communications between communication nodes. Further, since the use of the channel of the wavelength multiplex communication is controlled by the demand assignment by the packet communication system, crosstalk due to simultaneous use can be avoided.

In the above-described embodiment, an example is described in which the channel having the longest wavelength is used as a reference.

The components of the wavelength control node and the communication node to which the control method is applied are not limited to those described in the embodiment as long as they have similar functions. Is the same).
Further, the present invention is not limited to the described values as long as the numerical operation used in the embodiment is within the allowable range.

As described above, according to the first and second embodiments, a high-density wavelength division multiplexing communication system for maintaining a constant wavelength interval between adjacent channels in a wavelength division multiplexing communication system composed of distributed communication nodes. Therefore, it is not necessary to provide a wavelength tunable filter for detecting the wavelength allocation in a communication node in the system separately from a filter for receiving a wavelength-division multiplexed signal, thereby simplifying the configuration of the communication node and reducing the cost. it can.

Further, according to the first embodiment, in the above communication system, the reception function of the packet communication system of the wavelength control node becomes unnecessary, and the wavelength control node can be made inexpensive.

Further, according to the first embodiment and the second embodiment, in the communication system described above, it is possible to prevent interference at the start of light emission in the wavelength division multiplex communication system by the control packet signal.

[Third Embodiment] In the present embodiment, the provision of the wavelength control node as in the first and second embodiments makes the non-receiving communication node function as the wavelength control node. The wavelength tunable filter provided in the receiving unit of the communication node of the wavelength division multiplex communication system is used as the wavelength arrangement detecting means for controlling the wavelength.

In this embodiment, in the steady state, one of the communication nodes sends out a wavelength control packet and maintains the steady state. In an unsteady state (when a certain channel starts emitting light and stops emitting light), a communication node that receives a channel that has started emitting light for transmission or a channel that has stopped emitting light transmits a wavelength control packet, Transition to steady state.

Hereinafter, a detailed description will be given with reference to the drawings. FIG.
Is a system configuration diagram. The wavelength control node 6 from FIG.
1 and the optical fibers 62 and 63 are omitted. The terminal stations 211 to 21n transmit and receive electric signal data, and the communication nodes 221 to 22n are connected to the terminal stations 211 to 21n.
In addition to transmitting and receiving the optical signals and converting them into optical / electrical signals and having a wavelength control function described later, the star coupler 23 distributes the optical signals received from the optical fibers 241 to 24n to the optical fibers 251 to 25n. , A wavelength division multiplexing communication system is established.

FIG. 9 shows the transition of the wavelength control role in the wavelength control method of the present invention. The time axis is taken from the top to the bottom to indicate the transmission timing of the wavelength control packet (T1p1 to T1p15). T1da is 1
This is the transmission interval of the wavelength control packet while one communication node serves as the wavelength controller in the unsteady state. The figure shows an example of a state transition from I) steady state → II) unsteady state due to channel light emission start → III) steady state → IV) unsteady state due to channel light emission stop → V) steady state.

FIG. 10 shows the communication nodes 221 to 221 shown in FIG.
22n, which is different from FIG. 5 in that a detection signal for detecting the wavelength in the optical fiber is input from the light receiving element 58 to the wavelength control system 31 via the amplifier 316 and the discriminator 317, and the packet communication system Or the signal of the wavelength control system 31 is controlled.

More specifically, the wavelength control system 31 controls the wavelength tunable LD 52 via the wavelength tunable LD drive circuit 54 based on the contents of the wavelength control packet from the receiving circuit 511 of the packet communication system. To move or maintain the emission wavelength. Further, the wavelength of the tunable filter 53 is controlled via the tunable filter driving circuit 55.
At the time of reception in the wavelength division multiplex communication system, the wavelength of the wavelength tunable filter 53 is made to coincide with the wavelength of the channel addressed to the own station from the channels. At the time of non-reception, the wavelength of the wavelength tunable filter 53 is swept over the entire wavelength range of the wavelength division multiplex communication system, the wavelength arrangement is detected based on the output of the discriminator 317 at that time, and a wavelength control packet is generated.

The wavelength tunable LD 52 is a transmission light source for a wavelength division multiplex communication system. Further, the wavelength tunable filter 53 is used for reception of a wavelength multiplex communication system and detection of a wavelength arrangement.
Further, the wavelength variable LD driving circuit 54 is a voltage control type current source, and drives the wavelength variable LD 52 to inject a current so as to have a wavelength corresponding to a control signal from the wavelength control system 31.
I do. The wavelength tunable filter driving circuit 55 is a voltage control type voltage source. A wavelength control signal and a lock ON / OFF signal are input from the wavelength control system 31. When the receiving channel is selected and when the receiving channel is not received, the lock state is OFF. In order to scan the filtering wavelength, the wavelength variable filter 53 is driven to have a wavelength corresponding to the control signal from the wavelength control system 31. During reception, the lock is ON, and the wavelength of the wavelength tunable filter 53 is locked to the wavelength of the reception channel.

The optical modulator 56 and the optical modulator driving circuit 57 are provided with a wavelength tunable LD based on a transmission signal of a wavelength division multiplex communication system input from one of the terminal stations 211 to 21n.
This is for modulating the intensity of the output light of 52. When directly modulated by the current injected into the wavelength tunable LD 52, 0.1
Since a wavelength variation of about nm occurs, a method of external intensity modulation by the optical modulator 56 is preferably used.

The light receiving element 58 and the receiving circuit 59 are for receiving in a wavelength division multiplex communication system. The optical signal of the channel selected by the wavelength tunable filter 53 is converted into an electric signal, and is reproduced as, for example, communication information of a digital signal. The reproduced reception signal is output to the terminal station.

Further, the amplifier 316 amplifies the output of the light receiving element 58, and the discriminator 317 compares the signal with a threshold value.
Is output to the wavelength control system 31. Then, in correspondence with the control voltage supplied from the wavelength control system 31 to the wavelength tunable filter drive circuit 55, the wavelength control system 31 determines the wavelength of the channel on which the discriminator 317 outputs “1”. Or to detect.

The LD 47 is a light source of a packet communication system, and has a wavelength of, for example, 1.3 μm. The LD drive circuit 48 is a current source that modulates the LD 47 with a signal from the signal selection switch 318. In the present embodiment, high-density wavelength multiplexing is not performed in the packet communication system.
7 is directly intensity modulated.

The signal selection switch 318 selects one of the transmission signal of the packet communication system from the terminal station and the wavelength control packet from the wavelength control system 31, and selects the LD drive circuit 48.
To enter. Here, the wavelength control packet has priority. When two signals are simultaneously input, including data in the data format of the wavelength control packet shown in FIG. 3 described above, the transmission signal from the terminal station is saved in a buffer inside the wavelength control system 31, and the wavelength control packet is saved. Send after sending.

The light receiving element 510 and the receiving circuit 511 are for receiving a signal of a packet communication system.

The optical multiplexer 514 multiplexes the optical signal of the wavelength multiplexing communication system in the wavelength band of 1.5 μm and the optical signal of the packet communication system in the wavelength band of 1.3 μm, and outputs the multiplexed signal to the optical fiber. On the other hand, the optical demultiplexer 513 separates the optical signal input from the optical fiber by the wavelength band, inputs the optical signal of the 1.5 μm band to the wavelength tunable filter 53, and inputs the optical signal of the 1.3 μm band to the light receiving element 510. input.

In the present embodiment, all communication nodes have a possibility of detecting the wavelength arrangement using the tunable filter 53 in the non-receiving state. Sweeps the wavelength of the wavelength tunable filter 53 over the entire wavelength range of the wavelength division multiplex communication system,
The output of the discriminator 317 at that time is monitored, and the wavelength arrangement of each channel is detected.

In the steady state, one of the communication nodes in the non-receiving state serves as a wavelength controller, and in the unsteady state (when a certain channel starts emitting light and stops emitting light), the channel or the light emitting channel that started emitting light. In order to allow the communication node that receives the channel for which the transmission has been stopped (immediately before the start of reception and immediately after the end of reception) to serve as a wavelength controller, the timing of wavelength arrangement detection and transmission of a wavelength control packet is as follows. Here, immediately before the start of reception means a period from the unsteady state at the start of light emission to the steady state, and immediately after the end of reception, the state changes from the unsteady state to the steady state at the time of light emission stop of any communication node. Means until

The timing of wavelength arrangement detection and transmission of a wavelength control packet will be described below.

Immediately before the start of reception or immediately after the end of reception,
If the own node satisfies a condition for transmitting a wavelength control packet (described later) after the wavelength allocation detection immediately after the state is reached, the wavelength control packet is transmitted ΔT after the wavelength allocation detection, and T1da is transmitted from the transmission. −ΔT (ΔT is a time from detection of a wavelength arrangement to transmission of a wavelength control packet when a wavelength control packet is transmitted, and is a predetermined time shorter than T1da. ΔT is, for example, 0.5 × T1da. )) Then, the next wavelength arrangement detection is performed. After that, until the own node stops serving as the wavelength controller, the wavelength arrangement detection and the transmission of the wavelength control packet are performed in the T1da cycle. If the own node does not satisfy the condition for transmitting the wavelength control packet, the node receives the wavelength control packet transmitted by the other node. Therefore, the wavelength allocation is performed T1db after the reception of the wavelength control packet transmitted by the other node. It is controlled to perform detection.

Here, T1db is a predetermined time longer than T1da (for example, 2 × T1da), another node immediately before the start of reception or immediately after the end of reception serves as a wavelength controller, and the other node is T1da. As long as the wavelength control packet is transmitted at intervals, the own node receives the next wavelength control packet during T1db from reception of one wavelength control packet to detection of the next wavelength.
As long as the other node is transmitting the wavelength control packet at the T1da interval, it does not perform the wavelength allocation detection and the transmission of the wavelength control packet.

If the other node stops sending the wavelength control packet while the own node is in the state immediately before the start of the reception or immediately after the end of the reception, the node enters the state immediately before the start of the other reception or immediately after the end of the reception. Does not transmit the wavelength control packet, the condition for transmitting the wavelength control packet is satisfied, and the subsequent operation is performed.

Here, the condition for transmitting the wavelength control packet immediately before the start of reception or immediately after the end of reception is as follows.
This is “(1) No wavelength control packet is received during ΔT after wavelength arrangement detection”.

In the other non-reception state, if the own node satisfies the condition for transmitting a wavelength control packet (described later), the node transmits a wavelength control packet ΔT after the detection of the wavelength arrangement, and from the transmission, T1dc−ΔT (T1dc Is, for example, 2
× T1da) After that, wavelength arrangement detection is performed. If the condition for transmitting the wavelength control packet is not satisfied, the wavelength control packet transmitted by another node is received. Therefore, the wavelength arrangement detection is performed after T1dd from the reception of the wavelength control packet transmitted by the other node. Is controlled.
Here, T1dd is a predetermined time longer than T1dc (for example, 4 × T1da).

Here, the condition for transmitting a wavelength control packet in a non-reception state other than immediately before the start of reception or immediately after the end of reception is “(2) when no wavelength control packet is received during ΔT after detection of wavelength allocation”. is there. At this time,
It is preferable to add “(3) when the wavelength allocation is detected in the wavelength allocation detection” as unnecessary wavelength control packets are not generated.

If (2) is adopted as a condition for transmitting a wavelength control packet in a non-reception state other than immediately before the start of reception or immediately after the end of reception, and (3) is not adopted, the node performing the above operation will immediately Alternatively, until a node immediately after the end of the reception is generated, the wavelength allocation detection and the transmission of the wavelength control packet are performed at intervals of T1dc, and the other node that performs the above operation has a wavelength control role. As long as the node transmits a wavelength control packet at T1da or T1dc intervals, the own node must receive the next wavelength control packet during T1dd from reception of one wavelength control packet to detection of the next wavelength. , The other node transmits the wavelength control packet to T1d.
As long as the transmission is performed at the interval a or T1dc, the wavelength allocation detection and the transmission of the wavelength control packet are not performed. When the other node stops transmitting the wavelength control packet,
When another node does not transmit the wavelength control packet, the condition for transmitting the wavelength control packet is satisfied, and the subsequent operation is performed. Of course, when the own node is in a state immediately before the start of reception, the above-described operation or the above operation is performed.

When the above conditions (2) and (3) are adopted as conditions for transmitting a wavelength control packet in a non-reception state other than immediately before the start of reception or immediately after the end of reception, the node performing the above-mentioned operation is required to transmit the wavelength control packet. Even if the arrangement is detected, the wavelength control packet is not transmitted unless a deviation is detected. Therefore, if there is no deviation when a certain node is performing the above operation, one of the operating nodes may satisfy the condition of transmitting the wavelength control packet. Move to operation.

Here, the state in which the wavelength arrangement is deviated is included in the steady state, and the wavelength arrangement shown in FIG. This means that the arrangement is shifted. This deviation is detected based on the relationship between the output of the discriminator 317 and the voltage supplied to the wavelength tunable filter driving circuit 55.

As described above, by controlling each communication node, in the steady state, one of the communication nodes in the non-receiving state is set.
One serves as a wavelength controller, and T1dc
Transmit wavelength control packets at (or above) intervals,
S control is performed. At this time, if the node operating for some reason cannot send out the wavelength control packet, one of the other nodes performing the above operation becomes the wavelength controller and performs the above operation. When a node immediately before the start of reception or immediately after the end of reception occurs, the state shifts to an unsteady state, and the node in the state immediately before the start of reception or immediately after the end of reception serves as a wavelength controller. Sends a wavelength control packet. Here, T1da <T1db ensures that no other node will serve as a wavelength controller until the node operating as described above finishes transmitting the wavelength control packet. Further, since T1dc <T1dd, until the node performing the above operation ends transmission of the wavelength control packet, or until another node becomes a state immediately before reception start or a state immediately after reception end, It is assured that no other node will act as wavelength controller.
Further, especially when T1da <T1dc, the interval between wavelength shifts can be shortened in a state where a node occurs immediately before the start of reception or immediately after the end of reception, that is, in an unsteady state. In a steady state where wavelength bands can be used efficiently and wavelength shifts need not be performed promptly, the frequency of wavelength arrangement detection and transmission of wavelength control packets can be reduced, and the load of wavelength control can be reduced.

Next, a specific example of the shift of the wavelength controller shown in FIG. 9 will be described. In the example of this figure, there are five modes depending on the transition between the steady state and the unsteady state.

I) T1p1 to T1p4. The wavelength arrangement is in a steady state. Communication node X, which is one of the non-receiving communication nodes, is transmitting the wavelength control packet. As described above, the interval is at least T1dc.

II) T1p5 to T1p7. Channel A starts emitting light between T1p4 and T1p5, and the wavelength arrangement is in an unsteady state. The communication node A, which is a communication node to receive the channel A, receives a reception request in the packet communication system between T1p4 and T1p5, enters a state immediately before the start of reception, performs the above operation, performs transmission and reception of the wavelength control packet, and T1da-ΔT
To As a result, the communication node A sends out the wavelength control packet at the T1da period. By the collective FCS control using the wavelength control packet, the wavelength of the channel A becomes a wavelength interval of Δλ from the adjacent channel, and the wavelength arrangement is fixed. State. The communication node A, which has detected that the wavelength arrangement has become a steady state, adjusts the wavelength tunable filter to the wavelength of the channel A, and then confirms that the transmission source communication node of the channel A can receive data in the packet communication system. Then, reception on channel A is started. Since the communication node A has started the reception, it has come down from the communication control system.

III) T1p8 to T1p10. As in I), the communication node X sends out a communication control packet.

IV) T1p11 to T1p13. The channel B stops emitting light between T1p10 and T1p11, and the wavelength arrangement becomes an unsteady state. The communication node B that has received the channel B is in a state immediately after the end of the reception,
The above operation is performed, and the interval between transmission / reception of the wavelength control packet and detection of the wavelength arrangement is set to T1da. As a result, the communication node B sends out the wavelength control packet at the T1da period, the free wavelength region created by stopping the light emission of the channel B by the collective FCS control by the wavelength control packet is narrowed, and the wavelength arrangement is changed. It becomes a steady state.
The communication node B that has detected that the wavelength allocation has become a steady state sets the interval between transmission and reception of the wavelength control packet and detection of the wavelength allocation to T1dc.

V) T1p13 to T1p15. As in I), the communication node X sends a communication control packet.

When one-to-many communication is performed in a wavelength division multiplex system, there is no communication node in a non-reception state, although the number of available channels in the wavelength division multiplex communication system is smaller than the number of communication nodes. Can happen. In this situation, there is no communication node serving as the wavelength controller, and in some cases, interference between adjacent channels occurs. In this case, the communication node that has detected the interference stops receiving and informs the transmitting source communication node of stopping the reception in the packet communication system, and then serves as a wavelength controller. After the deviation of the wavelength arrangement is corrected, the wavelength of the optical filter is adjusted to the original reception channel, the transmission source is notified that the reception is possible, and the reception is started.

[0105] Alternatively, since there is almost no case where a communication node that performs one-to-many communication information transmission is received by its own reception unit, the communication node transmits the communication control packet to the communication packet system while transmitting the communication control packet to the communication packet system. A control packet can be transmitted to serve as a wavelength controller.

In this embodiment, the wavelength controller can be shifted without communication in the packet communication system, and unnecessary traffic is not generated in the packet communication system.

[Fourth Embodiment] In this embodiment, the wavelength controller is shifted by communication in a packet communication system. When the network is activated, one communication node becomes the wavelength controller, and notifies the other communication nodes of the termination of the wavelength controller before the node itself enters the reception state. The communication node in the non-reception state that has received this notification makes a notification that the wavelength controller is possible. The communication node currently serving as the wavelength controller selects one of the communication nodes that has issued the wavelength controller enable notification, and notifies the wavelength changer of the wavelength controller to the communication node using a packet communication system. The communication node that has received the wavelength control role transfer notification becomes the wavelength control role. When the communication node enters the receiving state, the wavelength controller is shifted by the same procedure.

The wavelength division multiplexing communication system according to the present embodiment is the same as that shown in FIG. 8, and the configuration of the communication node is the same as that shown in FIG.

FIG. 11 shows an example of the shift of the wavelength controller in this embodiment. The time axis is taken from the top to the bottom to indicate the transmission timing of the wavelength control packet (T2
p1 to T2p14). Here, T2p4 to T2p11
Is enlarged because packet communication for migration is performed densely. T2d is a repetition period of the wavelength arrangement detection of the communication node serving as the wavelength controller. The communication node serving as the wavelength controller transmits the wavelength control packet only when a deviation in the wavelength arrangement is detected (including the unsteady state). As a result, the shortest transmission interval of the wavelength control packet is T2d. The figure shows a situation where the wavelength controller has shifted from the communication node A to the communication node B.

In the present embodiment, since the wavelength control role is reliably shifted, if a wavelength arrangement shifts in a steady state, the shift can be resolved without fail and interference between adjacent channels can be prevented.

In FIG. 11, timings T2p1 to T2p1
In 2p4, the communication node A serving as a wavelength controller sweeps the wavelength of the optical signal in the transmission path of the receiving optical fiber, detects the channel number and the wavelength, and performs the operation described in the third embodiment. In the same manner as described above, the control information relating to the maintenance / shift of the wavelength is transmitted as a wavelength control packet. Timing T2
Before p5, the communication node A needs to receive the information. Therefore, at T2p5, the communication node A sends an end notification of the wavelength controller to the effect that the own station ends the wavelength controller to the packet communication system.
In response to this end notification, the communication node B in T2p6
At T2p7, the communication node C notifies the communication node A of the wavelength controller role through the packet communication system to the communication node A at T2p8. In T2p9, the communication node A normally sends out a wavelength control packet in the same manner. Furthermore, T2p10
Then, the communication node B is selected from among the communication nodes that have received the notification that the wavelength controller can be used, and a shift notification of the wavelength controller is sent to the communication node B to the packet communication system.

Then, the communication node B sweeps the wavelength of the wavelength tunable filter of its own station through the packet communication system through the packet communication system, detects the wavelength arrangement of the optical signal of the wavelength multiplex communication system, and at the timing T2p11, the communication node B As in the data format of the wavelength control packet transmitted by A, the wavelength control packet is transmitted to the packet communication system as a wavelength controller. At timings T2p12 to T2p14, the communication node B continuously sends out the wavelength control packet, and continues until the reception state is reached.

[Fifth Embodiment] In this embodiment, when operating as a wavelength controller, a transmission packet from a terminal station is
A method for avoiding collision with a wavelength control packet in a transmission unit of a packet communication system will be described.

In the configuration of the communication node shown in FIG. 10, an example is described in which the wavelength control packet is transmitted from the wavelength control system 31 to the LD drive circuit 48 via the signal selection switch 318 as the transmission path of the wavelength control packet. Once the data of the wavelength control packet is sent to the terminal station, the terminal station properly arranges the data of the packet communication system packet serving as a communication controller and the data of the terminal station itself to transmit in the packet communication system. Then, it may be directly input to the LD drive circuit 48 as a transmission signal. In this case, the signal selection switch 3
18 becomes unnecessary.

The other components are not limited to those described in the third to fifth embodiments as long as they have the same function. The same applies to a system composed of several components.

In the above-described embodiment, an example is shown in which all communication nodes are provided with a wavelength control packet system. However, due to cost requirements and empirical rules in the system, not all communication nodes are used. The wavelength control packet system may be configured in a plurality of communication nodes. In this case, the wavelength control role can be limited to the plurality of communication nodes. However, the communication possibility and the communication stability can be improved as compared with one or two wavelength control nodes described in the first and second embodiments. It is effective in terms of communication reliability.

As described above, in the third to fifth embodiments, the communication node in the non-receiving state serves as a wavelength controller, so that each communication node is connected to the wavelength detecting means (wavelength filter) for reception. It is not necessary to provide both of the wavelength detection means for arrangement detection, and it is possible to eliminate the need for a dedicated wavelength control node in the case described in the first and second embodiments. Further, according to the third to fifth embodiments, in the unsteady state in which wavelength control must be performed frequently, the wavelength controller can surely transmit the wavelength control packet.

Further, according to the third embodiment, the wavelength controller can be shifted without communication in the packet communication system, and unnecessary traffic is not generated in the packet communication system. Further, according to the third to fifth embodiments, since the wavelength control role is reliably shifted, when the wavelength arrangement is shifted in the steady state, the shift is surely eliminated, and the distance between adjacent channels can be reduced. Interference can be prevented.

[Sixth Embodiment] In this embodiment, two wavelength control nodes are installed in the network of the wavelength division multiplexing communication system, and one wavelength control node according to the first and second embodiments fails. However, the remaining wavelength control nodes send out wavelength control packets so that the wavelength control of the communication nodes can be performed.

In this embodiment, the wavelength control node has a transmission / reception function of a packet communication system. Of the two wavelength control nodes, one is mainly in operation at present and one is spare.
The currently operating wavelength control node continues to transmit wavelength control packets at regular time intervals. The spare wavelength control node monitors the wavelength control packet interval by the currently operating wavelength control node, and if the interval becomes longer than a predetermined time, determines that the currently operating wavelength control node has failed, and And starts transmitting the wavelength control packet.

Hereinafter, the present embodiment will be described in detail with reference to the drawings.

FIG. 12 is a configuration diagram of a wavelength division multiplexing communication system to which the present embodiment is applied. The difference from FIG. 1 is that there are two wavelength control nodes 361, 362 and optical fibers 371, 372, 381, 382 for connection.

The operating wavelength control node I 361 is
(1) Standby, (2) Detection / detection of wavelength arrangement of wavelength multiplex communication system, (3) Shift of wavelength of transmitter of each communication node to keep wavelength interval of each channel of communication nodes 321 to 32n constant A series of operation cycles of calculating the direction and (4) transmitting the wavelength control packet are repeated at a constant period T3da. Here, (1) standby is for waiting for the wavelength control packet to be received by all communication nodes in the network and for each communication node to complete the shift of the transmission wavelength.

The wavelength control nodes 361 and 362
Is the same as that described with reference to FIG. 4, and a description thereof will be omitted. The packet communication system and the wavelength multiplexing communication system used by the wavelength control node I361, the wavelength control node II 362 and the communication node are the same as the method used in the first embodiment, and the configuration of the communication nodes 321 to 32n is shown in FIG. Since they are the same as those described in,
It will be described in the first embodiment.

FIG. 12 is an explanatory diagram showing an operation example of the wavelength control node in the sixth embodiment. Here, the manner in which the wavelength control packet is transmitted is shown. The time axis is taken from the top to the bottom to show the timing of the operation of the wavelength control node (transmission of a wavelength control packet, detection of failure). T
3p1 to T3p4, T3p6, and T3p7 are for transmitting a wavelength control packet, and T3p5 is for when a failure is detected. Also, T3da is the transmission interval of the wavelength control packet when the wavelength control node I 361 is operating normally, T3db is the interval at which the spare wavelength control node II 362 considers that the operating wavelength control node has failed, and T3dc is the spare interval. This is the time required from when the wavelength control node II 362 detects the failure of the operating wavelength control node I 361 to when the first wavelength control packet is transmitted. T3da and T3db have a margin for a packet propagation delay due to a topology or a protocol.

The operating wavelength control node I 361 detects the wavelength arrangement of the wavelength division multiplexing communication system, and sets the wavelength of the transmitter of each communication node to make the wavelength interval of each channel transmitting in each communication node constant. Calculation of the shift direction and transmission of the wavelength control packet are repeated at a constant cycle T3da. As a result, the wavelength control packet is transmitted to the network at regular intervals T1da. In the example of FIG. 1, T3p1 to T3p
Up to 4 wavelength control packets are transmitted at 31 da intervals.

The spare wavelength control node II 362 counts the transmission time of the wavelength control packet of the wavelength control node I by a counter in the wavelength control system 41, and determines the failure of the operating wavelength control node I based on the transmission time interval. Is detected. If the next wavelength control packet is not received during the time T3db after receiving a certain wavelength control packet, it is determined that the operating wavelength control node I has failed, and the wavelength control node
II takes over and starts operating as the primary wavelength control node. In the example of FIG. 13, T3 is between T1p4 and T1p5.
Since the wavelength control packet has not been transmitted through the optical fiber for a time equal to or longer than db, it is determined that the operating wavelength control node I has failed. The spare wavelength control node II is T3p
Since the wavelength control packet was not received during T3p5 after receiving the wavelength control packet in 4, operation starts as the main wavelength control node. After detecting the transmission wavelength of each communication node of the optical fiber and calculating the wavelength shift direction, the wavelength control node II calculates T3p6 (from T3p4 to T3p4).
After 3db + T3dc), a wavelength control packet is transmitted.
T3dc is the time over which the "standby" portion is omitted in a series of operations of the wavelength control node II (T3dc <T3da). Thereafter, the operation as the main wavelength control node is repeated, and T3
Transmit wavelength control packets at da intervals (T3p in FIG. 1)
6, T3p7).

The difference between the primary and secondary wavelength control nodes is a formal one, and their configuration and operation are not different. After the start of operation, the spare wavelength control node II becomes the main wavelength control node.

The wavelength control packet transmitted by the wavelength control node to each communication node may be in the data format of FIG. 3 used in the first embodiment, and a sender address is added similarly to other packets. May be. When the sender address is added, the network manager can identify the failed wavelength control node by monitoring the sender address of the wavelength control packet. In the example of FIG.
The sender of the wavelength control packets from 3p1 to T3p4 is the wavelength control node I, and the sender of the wavelength control packets of T3p6 and T3p7 is the wavelength control node II. T3p
Since the sender address changes between 4 and T3p6, T3p4
It can be seen that the wavelength control node I that has been operating up to now has failed. As a result, the wavelength control node I can be removed from the network, repaired, connected to the network again, and prepared for failure of the wavelength control node II.

In the above-described embodiment, an example is shown in which two wavelength control nodes are provided. However, two or more wavelength control nodes may be provided. This improves the configuration.

[Seventh Embodiment] In the present embodiment, the wavelength control node has a transmission / reception function of a packet communication system, similarly to the sixth embodiment. The two wavelength control nodes operate simultaneously, and when both are operating normally, alternately transmit wavelength control packets. The configurations of the wavelength division multiplexing communication system, the wavelength control node, and each communication node are the same as those described in the sixth embodiment, and a detailed description thereof will be omitted.

Hereinafter, the present embodiment will be described with reference to FIG. FIG. 14 is an explanatory diagram illustrating an example of the operation of the wavelength control node in the seventh embodiment. The figure shows how a wavelength control packet is transmitted. The time axis is taken from the top to the bottom to show the timing of the operation of the wavelength control node (transmission of the wavelength control packet). T4p1,
T4p2,..., T4p7 are transmission timings of the wavelength control packet. T4da is the wavelength control node I36.
1, the wavelength control node II 362 is operating normally, the transmission interval of the wavelength control packet, T4db is one of the wavelength control nodes, here the wavelength control node I fails, and the other wavelength control node This is the wavelength control packet interval when only the node, here, the wavelength control node II is operating. Each of the intervals T4da and T4db has a margin for a packet propagation delay due to the topology or the protocol.

In this embodiment, in the normal state, two wavelength control nodes operate simultaneously, and transmit wavelength control packets alternately. For this purpose, the operation cycle of the wavelength control node is performed starting from the reception of the wavelength control packet, and two values are set in the “standby” time. T4da is the "standby" time of the operation cycle after receiving the wavelength control packet transmitted by the wavelength control node other than its own, T4d
b is the "standby" time of the operation cycle after receiving the wavelength control packet transmitted by itself. If a wavelength control packet is received in the middle of an operation cycle, the operation is reset and a new operation cycle is started. T4da <T4
By setting db, transmission of wavelength control packets of two wavelength control nodes in a normal state can be performed alternately.

In the example of FIG. 14, from T4p1 to T4p6, the wavelength control node I and the wavelength control node II alternately transmit the wavelength control packet at the interval T4da. T4p
6 and T4p7, wavelength control node I fails and T4p
Since the wavelength control packet is not transmitted from the wavelength control node I after T4da from T4da, the operation cycle of the wavelength control node II is not reset, and the wavelength control packet is transmitted from the wavelength control node II to T4p7 after T4db from T4p6. Thereafter, the operation cycle of the wavelength control node II is not reset, and the wavelength control packet is transmitted from the wavelength control node II at intervals of T4db (T4p in FIG. 14).
8).

The determination of the failed wavelength control node can be performed by monitoring the sender address of the wavelength control packet as in the sixth embodiment. In the example of FIG. 14, the wavelength control packets are alternately received from the two wavelength control nodes from timing T4p1 to T4p6,
After the timing T4p7, a wavelength control packet to which a sender address (address of the wavelength control node II) is added is received only from the wavelength control node II. This indicates that the wavelength control node I has failed after the timing T4p7. If the failure of the wavelength control node I is perceived by the network administrator, the wavelength control node I is removed from the network, repaired, connected to the network again, and the two wavelength control nodes again transmit wavelength control packets alternately. Can be

In the above embodiment, since the two units are simultaneously operated and the transmissions are alternately operated, the same load is applied to the two units, the frequency of failures is the same for both units, and the system balance is improved.

[Eighth Embodiment] In this embodiment, the wavelength control node has only the transmission function of the packet communication system. Each configuration of the wavelength division multiplexing communication system, the wavelength control node, and the communication node is the same as that described in the sixth embodiment. Of the two wavelength control nodes, one mainly operates at present and one becomes a standby, and performs the same packet communication system operation as in the seventh embodiment. The currently operating wavelength control node keeps transmitting the wavelength control packet at a fixed time interval T5. The spare wavelength control node performs only the wavelength detection and monitors the wavelength arrangement in the transmission path. Then, in the following two cases, it is determined that the currently operating main wavelength control node has failed, and instead, the operation is started from the spare as the main wavelength control node, and transmission of the wavelength control packet is started. (1) When the wavelength interval of the channel adjacent to the transmission wavelength by the communication node becomes smaller than the preset channel interval (for example, ／ of the channel interval), (2) the transmission wavelength by the communication node is adjacent. If the channel wavelength spacing is
If the wavelength interval does not become smaller than the predetermined channel interval (for example, 2 times) and sufficiently longer than the time interval T5 (for example, 5 times T5), the node is a spare wavelength control node. However, as a main wavelength control node, it transmits a wavelength control packet and controls the transmission wavelength of each communication node.

Incidentally, the determination of the failed wavelength control node and the like are the same as in the sixth embodiment.

According to the eighth embodiment, since the wavelength control node sends out the wavelength control packet based on the detected wavelength arrangement regardless of the reception timing of the wavelength control packet, each wavelength control node transmits a packet communication system. There is no need to have a receiving function, and the configuration is simplified.

Further, the detection of the failure of the main wavelength control node in the sixth embodiment can be performed at intervals other than the transmission interval of the wavelength control packet. For example, the backup wavelength control node may communicate with the main wavelength control node at regular time intervals in a packet communication system, and monitor the operation state.

It is also possible to prevent the transmission of the wavelength control packets in the seventh embodiment from being performed alternately.
For example, by making the “standby” time of the operation cycle of the wavelength control node I shorter than the “standby” time of the wavelength control node II, the wavelength control node I is operating while the wavelength control node I is operating.
There is also a method in which only the wavelength control packet is transmitted.

Further, a specific example of the wavelength interval and time for detecting the failure of the main wavelength control node in the eighth embodiment may be other values as long as the operation of the communication system is not hindered. .

According to the sixth to eighth embodiments, when one wavelength control node fails, the wavelength division multiplex communication system can be operated normally. Further, according to the sixth to eighth embodiments, the wavelength control function is automatically shifted to another wavelength control node, and the wavelength division multiplexing communication system can operate normally. Further, when the failed wavelength control node is removed from the network, repaired, and connected to the network again, there is no need to stop the operation of the network.

[Ninth Embodiment] In each of the above embodiments, the configuration in which the wavelength control node connected to the network system or the communication node serving as the wavelength controller transmits the wavelength control packet has been described. It is not limited. In the present embodiment, a configuration in which a wavelength control packet generating unit is provided near the star coupler is adopted.

In FIG. 3 of Journal of Lightwave Technology, Vol. 11, No. 5/6, p. 1089, each communication node sends a connection request to a center node composed of an optical coupler and a control circuit, and the request is transmitted. A configuration is disclosed in which a wavelength (optical frequency) is assigned by processing in a control circuit. On the other hand, in the present embodiment, high-density wavelength multiplexing is enabled without absolutely fixing the wavelength by using a center node having an optical coupler and a means for controlling FCS.

FIG. 15 is a block diagram of a center node used in this embodiment. This center node corresponds to the star coupler used in the previous embodiment (N + 1) ×
It has an (N + 1) optical coupler 201, a wavelength allocation detection system 205 for performing FCS control, an optical transmitter 206, and a wavelength multiplexing communication control system 208.

FIG. 16 shows the configuration of a network in this embodiment. Each of the optical (communication) nodes 321, 322,.
2n are connected by optical fibers of an optical transmission line, and terminals 311, 312,... 31n are connected respectively.

In this embodiment, the center node 1
The wavelength arrangement detection system 205 in 501 includes a wavelength tunable filter, a light receiving element that receives a transmission wavelength of the wavelength tunable filter, and an identifier that identifies the received output, as in the above-described embodiments. Here, the wavelength arrangement is detected. The wavelength multiplexing communication control system 208 generates a wavelength control packet for FCS control such as wavelength shift and wavelength maintenance based on the result, and sends it out by the optical transmitter 206. Each communication node can realize high-density wavelength multiplexing by controlling the wavelength of transmission light of the own node based on the transmitted wavelength control packet. Also in this configuration, each communication node can perform FCS control without providing a wavelength arrangement detecting unit separately from a wavelength selecting unit (wavelength variable filter) for receiving a wavelength multiplexed signal.

[Tenth Embodiment] As in the ninth embodiment described above, the optical signal from each communication node is concentrated, that is, the center node is provided with a wavelength control function, and is transmitted from each communication node. When a problem such as interference occurs in the wavelength of an optical signal, optical path control can be performed.

FIG. 17 is a block diagram of an optical center node that performs the above optical path control. The number of communication nodes is N. In FIG. 17, (N + 1) × (N
+1) The optical coupler 201 distributes optical signals input from the N + 1 optical input ports to the N + 1 optical output ports. The output of the optical transmitter 206 inside the optical center node;
And an optical signal from each communication node and input from N + 1 optical fibers, and an optical receiver 20 inside the optical center node.
Distribution is performed in seven directions and to output N + 1 pieces to each communication node. This (N + 1) × (N + 1) optical coupler 20
For example, a quartz optical waveguide formed on a silicon substrate can be used, for example, as described in the document “C. Dragone, CHHen
ry, IPKaminow, and RCKistler: "Efficient multich
annel integrated optics star coupler on sillicon ",
IEEE Photonics Technol. Lett., Vol. 1, No.8, pp.2
41 to 243 (Aug. 1989) ". .

The N × 1 optical coupler 202 multiplexes the optical signals input from the N optical input ports from each communication node and outputs the multiplexed optical signal to one optical output port. The optical multiplexed signal from each communication node is input to the 2 × 1 optical coupler 203.

The 2 × 1 optical coupler 203 multiplexes the optical signals input from the two optical input ports and connects them to one optical output port. (N + 1) × (N + 1) optical coupler 2
01 and the outputs of the N × 1 optical coupler 202 are input to the optical demultiplexer 204.

The optical demultiplexer 204 separates the wavelength in the 1.3 μm band from the wavelength in the 1.5 μm band. This optical demultiplexer 204
Can use band pass filters that transmit wavelengths of 1.3 μm band and 1.5 μm band, respectively. For example, AO filter, EO filter, tunable DFB filter, Mach Cender filter, Fabry-Perot filter, dielectric multilayer filter Etc. can be used.

Next, the wavelength allocation detection system 205 is used for the wavelength division multiplexing communication system input from the optical demultiplexer 204, for 1.5.
The arrangement of wavelengths in the μm band is detected, and the result is transmitted to the wavelength division multiplexing communication control system 208. The wavelength arrangement detection system 205 includes a wavelength tunable filter, a wavelength tunable filter control circuit that applies a control voltage to the wavelength tunable filter, and sweeps a wavelength, and a photodetector that receives an output of the wavelength tunable filter and converts the output into an electric signal. A wavelength detector for detecting the wavelength allocation of the wavelength division multiplexing communication system from the conversion element, the discriminator for outputting only a component of the electric signal having a predetermined level or more, and the output of the discriminator and the control voltage to the wavelength tunable filter control circuit. And a circuit.

The optical transmitter 206 is an optical transmitter for packet communication. A packet signal (electric signal; wavelength control packet, etc.) from the wavelength multiplexing communication control
It is converted into an optical signal having a wavelength in the μm band and transmitted. The optical transmitter 206 includes, for example, a wavelength-variable light source, a modulator, and a driving circuit, and emits a predetermined 1.3 μm band wavelength based on a control signal from the wavelength multiplexing communication control system 208 to the driving circuit. The wavelength variable light source is driven, and the light emission wavelength is intensity-modulated with a packet signal, for example, and output.

The optical receiver 207 is an optical receiver for packet communication. 1. Input from the optical demultiplexer 204
The packet signal (optical signal) having a wavelength in the 3 μm band is converted into an electric signal and transmitted to the wavelength multiplex communication control system 208. The optical receiver 207 includes, for example, a variable wavelength filter and a photoelectric conversion element.

The wavelength division multiplexing communication control system 208 includes the optical transmitter 2
The wavelength allocation of the wavelength division multiplex communication system is performed by packet communication using the optical receiver 06 and the optical receiver 207. That is, in the packet communication, a reception request command and wavelength control data from each communication node are transmitted as a packet. Further, other information may be transmitted in this packet. Further, based on the information on the wavelength arrangement of the 1.5 μm band from the wavelength arrangement detection system 205,
The wavelength of the wavelength variable optical transmitter of each optical node is controlled by a packet communication system. Further, 1 × 2 optical switches 111 and 11
2 is controlled.

Next, the 1 × 2 optical switches 111 and 112
Is a one-input, two-output optical switch for connecting an optical signal input from an optical input port to one of two optical output ports by a control signal from the outside (here, a wavelength division multiplexing communication control system 208). The 1 × 2 optical switches 111 and 112 are controlled by the wavelength division multiplexing communication control system 208 and convert an optical signal input from an optical node into an (N + 1) × (N + 1) optical coupler 201.
Alternatively, the signal is output to the N × 1 optical coupler 202.

The optical input ports 121 and 122 and the optical output ports 131 and 132 are an optical input port and an optical output port of the optical center node, and are connected to the optical nodes via optical fibers. The optical input ports 121 and 122 are connected to the 1 × 2 optical switch 111 by optical fibers 141 and 142.
112. On the other hand, the optical output ports 131 and 13
2 is (N + 1) × by the optical fibers 151 and 152
(N + 1) is connected to the optical coupler 201.

The optical fibers 161 and 162 connect the 1 × 2 optical switches 111 and 112 and the (N + 1) × (N + 1) optical coupler 201. Optical fibers 171 and 172 are 1 × 2
The optical switches 111 and 112 and the N × 1 optical coupler 202 are connected.

1 × 2 optical switches 111 and 112, optical input ports 121 and 122, optical output ports 131 and 132,
Optical fibers 141, 142, 151, 152, 161;
Although 162, 171, and 172 show two communication nodes for the sake of simplicity, N systems are provided in a system having N communication nodes.

The optical fiber 181 is connected to the optical transmitter 207 (N
+1) × (N + 1) optical coupler 201 is connected. The optical fiber 182 connects the (N + 1) × (N + 1) optical coupler 201 and the 2 × 1 optical coupler 203. The optical fiber 183 connects the N × 1 optical coupler 202 and the 2 × 1 optical coupler 203. The optical fiber 184 includes a 2 × 1 coupler and the optical demultiplexer 204.
Connect. The optical fiber 185 is connected to 1.
The 5 μm band optical output port is connected to the wavelength arrangement detection system 205. The optical fiber 186 is 1.3 μm of the optical splitter 204.
The optical output port of the band and the optical receiver 206 are connected.

Hereinafter, the operation of this embodiment will be described. In the present embodiment, by switching the optical path in the optical center node, it is possible to prevent the wavelength of the optical node during wavelength setting or runaway of the wavelength multiplex communication system from interfering with another wavelength of the wavelength multiplex communication system. Further, in the present embodiment,
The optical path is switched by detecting the wavelength arrangement of the wavelength division multiplex communication system in the optical center node. A 1 × 2 optical switch is used for switching the optical path.

The optical path has the following two connections. (A) “Optical center node connection” state This is a connection in which an optical signal is transmitted from an optical node to only the optical center node. Connections to all communication nodes in the network are cut off. The communication node is specifically described as follows.

Optical input port 121 → optical fiber 141 →
1 × 2 optical switch 111 → optical fiber 171 → N × 1 optical coupler 202 → optical fiber 183 → 2 × 1 optical coupler 20
3 → Optical Demultiplexer 204 → Subsequently divided into two paths depending on the wavelength band. (A) 1.5 μm band (Wavelength multiplex communication system) → Optical fiber 1
85 → wavelength allocation detection system 205 → wavelength multiplex communication control system 20
8 (b) 1.3 μm band (packet communication system) → optical fiber 1
86 → optical receiver 206 → wavelength multiplex communication control system 208.

In this connection, since the optical signal of the packet communication system is not transmitted to other than the optical center node,
The packet transmitted by the connected communication node is reproduced and relayed by the wavelength division multiplexing communication control system of the optical center node. (B) “All optical node connection” state This is a connection in which an optical signal from an optical node is transmitted to an optical center node and all communication nodes. The communication node is specifically described as follows.

Optical input port 121 → optical fiber 141 →
1 × 2 optical switch 111 → optical fiber 161 → (N +
1) × (N + 1) optical coupler 201 → After that, it is distributed to the following path. (A) → optical fiber 182 → 2 × 1 optical coupler 203 → same as optical center node connection, (b) → optical fiber 151 → optical output port 131 → to optical node 1 (c) → optical fiber 152 → optical output From the port 132 to the optical node 2 The optical center node normally connects each port “all optical nodes” while detecting the wavelength arrangement of the wavelength division multiplex communication system. When a communication node (hereinafter, tentatively referred to as a communication node A in the present embodiment) requests use of a wavelength division multiplex communication system through packet communication, it is determined whether there is a communicable wavelength range in the wavelength range of the wavelength division multiplex communication system. Location detection system 20
The surplus wavelengths are checked by comparing the number of wavelengths with the stored arrangement wavelengths based on the wavelength arrangement based on the electric signal transmitted from No. 5. If there is a communicable wavelength range, the optical input port connected to the communication node A is set to “optical center node connection” so that the optical signal from the communication node A is not transmitted to other than the optical center node. . After that, the use permission of the wavelength multiplexing communication system, the assignment of the wavelength, and the like are transmitted to the communication node A via the optical transmitter through the packet communication, and any one of the remaining wavelengths is specified and instructed. Thereafter, the wavelength arrangement of the wavelength division multiplex communication system is continuously detected, and after confirming that the emission wavelength of the communication node A has not interfered with other wavelengths of the wavelength division multiplex communication system, the port connected to the communication node A is set to " Set to "All-optical node connection". After that, the transmission start permission is transmitted to the communication node A, and the communication node A that has received the transmission start starts transmission in the wavelength division multiplex communication system.

The operation of the optical center node when setting the wavelength of the wavelength tunable optical transmitter of the communication node has been described above. Next, the wavelength tunable optical transmitter of the communication node (referred to as communication node B) goes out of control. A description will now be given of a failure avoidance operation performed by the optical center node when the wavelength approaches the wavelength of an adjacent channel in the wavelength division multiplex communication system.

In the present embodiment, since the optical center node always monitors the wavelength arrangement of the wavelength division multiplex communication system, the wavelength variable optical transmitter of a certain communication node B in the network goes out of control and the wavelength division multiplex communication system becomes adjacent. It is possible to detect that the wavelength of the channel is approaching. If there is a channel having a predetermined wavelength interval (for example, a minimum wavelength interval that does not cause interference) with respect to the wavelength of an adjacent channel, the communication node B using the channel is connected. The input port is set to "optical center node connection" so that the optical signal of the communication node B is not transmitted to all communication nodes in the network. afterwards,
After continuing to detect the wavelength arrangement of the normal wavelength division multiplex communication system and confirming that the emission wavelength of the communication node B has reached the preset wavelength interval of the wavelength division multiplex communication system, the connection port of the communication node B is changed. Set to "All-optical node connection". afterwards,
The transmission start permission is transmitted to the communication node B, and the communication node B receiving the transmission permission transmits the "optical center node connection" in the wavelength division multiplex communication system.
Resume transmission from the point set in. In this way, adjacent channels can be prevented from receiving interference. In this case, even when the emission wavelength of the communication node goes out of control, the same control is performed on communication nodes that deviate from the preset wavelength interval.

The optical center node constantly monitors the wavelength arrangement of the wavelength division multiplex communication system, and switches the internal optical path as described above, thereby setting the wavelength setting of the wavelength variable optical transmitter of the communication node to the wavelength of another channel. This can be done without interference. Further, when there is a communication node in which the wavelength tunable optical transmitter goes out of control, it is possible to avoid interference with an adjacent channel.

Although an example has been shown in which the respective functional blocks in the optical center node are connected by optical fibers, they may be directly connected without using optical fibers due to the configuration. In particular, optical fibers 184, 185, 186, etc. The connection can be shortened and downsized by using a waveguide having a dagger configuration. Further, the wavelength allocation detection system 205, the optical receiver 207, the optical transmitter 206, and the like need not be limited to the above-described configuration, but may have another configuration.

[Eleventh Embodiment] The eleventh embodiment of the present invention will be described below in detail with reference to the drawings. Eleventh
The embodiment is an example in which the optical center node of the present invention is used in a wavelength control method suitable for high-density wavelength multiplexing having a narrow wavelength interval. The configuration of the optical center node is the same as that described in the ninth embodiment.

FIG. 18 shows the operation of the wavelength control system. The wavelength arrangement of the wavelength division multiplex communication system is shown for seven states, with the wavelength on the horizontal axis and the wavelength of each optical node on the vertical line. In the figure, Δλ is the wavelength interval between two adjacent wavelengths maintained by control, and is a value obtained by adding a margin to the minimum wavelength interval at which two adjacent channels in a wavelength division multiplex communication system do not cause interference. Also, λA, λB, λC, and λD are the wavelengths of the optical nodes used in an example of the operation.

Here, this wavelength control method will be briefly described. In this wavelength control method, the wavelength allocation by the optical center node is not performed at an absolute wavelength, but at a relative wavelength for controlling a wavelength interval from an emission wavelength of an adjacent communication node. The optical center node operates its own wavelength arrangement detection system at fixed time intervals, and controls the wavelengths of all communication nodes emitting light in the wavelength band of the wavelength division multiplex communication system based on the result. This control is performed using a packet communication system, and is performed such that the wavelength of the wavelength variable transmitter of each communication node that emits light maintains a constant wavelength interval Δλ with an adjacent wavelength within the wavelength variable range. As a result, as shown in FIG. 18A, several groups are arranged in the wavelength arrangement at a wavelength interval of Δλ.

As a specific example, a case where the communication node D starts transmission in the wavelength division multiplex communication system (FIG. 18 (1) to FIG. 18)
(4)) and the case where the communication node B ends transmission in the wavelength division multiplex communication system (FIGS. 18 (5) to 18 (7)).

(A) When the communication node D starts transmission in the wavelength division multiplex communication system First, the wavelengths transmitted by the optical fibers 151 and 152 are five, three and three as shown in FIG. A total of 1
It is assumed that there is one wavelength, three groups are formed, and mutual transmission and reception are performed by 11 waves. Next, the communication node D sends a wavelength multiplex communication system use request to the optical center node by a packet communication system to start transmission. The optical center node receiving this transmits a wavelength multiplex communication system use permission to the communication node D by the packet communication system. Upon receiving this, the communication node D emits the wavelength of its own wavelength-variable optical transmitter (FIG. 18 (2)). The wavelength at this time may be anywhere in the wavelength variable range of the wavelength variable optical transmitter, but here, it is assumed to be near the center. The optical center node recognizes this wavelength newly appearing in the wavelength arrangement as the wavelength λD of the communication node D. Thereafter, the optical center node shifts the wavelength λD until the wavelength interval from the adjacent wavelength λC becomes Δλ (here, shifts to the shorter wavelength side. FIG. 18).
(3)) After the wavelength interval of Δλ is reached, control is performed so as to maintain the wavelength interval of Δλ (referred to as a steady state).
(4)).

(B) When the communication node B completes transmission in the wavelength division multiplex communication system From the state shown in FIG. 18 (4), the communication node B terminates transmission in the wavelength division multiplex communication system and Stop emitting light from the transmitter. The optical center node detects that the wavelength interval between the wavelengths λA and λC has become larger than Δλ. The optical center node controls so that the wavelength interval between adjacent channels in the group of the wavelength arrangement in which the wavelength λB has entered becomes Δλ. The wavelengths λA, λC, λ that belonged to this group
The wavelength of the first light emitted from D (assuming here that λA
), The wavelengths of the wavelength tunable optical transmitters of the communication nodes A and B are controlled such that λC and λD are each at a wavelength interval of Δλ (here, the wavelength is shifted to the longer wavelength side. (6)). By this control, after the wavelength interval between the wavelengths λA and λC, and the wavelengths λC and λD, which have been emitting light for the first time, become equal to Δλ, the state is controlled so as to be maintained (referred to as a steady state). FIG.
(7)).

In the wavelength control method described above, FIG.
When the wavelength tunable optical transmitter of the communication node D emits light in (2), interference may occur with another channel in the wavelength arrangement (here, interference with the wavelength λC). To avoid this, in the optical center node of the present invention, the wavelength multiplex communication system use permission is transmitted to the communication node, and at the same time, the optical input port connected to the communication node is connected to the "optical center node connection" (tenth embodiment). To avoid interference with other channels. Then, after the wavelength interval between adjacent channels becomes Δλ (FIG. 18D),
Connect the input port of the communication node D to "all communication node connection".
(Described in the tenth embodiment), and the communication node D
Of the wavelength tunable optical transmitter is distributed to all communication nodes. Thereafter, the optical center node continues to control the wavelength allocation by the wavelength allocation detection system based on the relative wavelengths having a constant wavelength interval.

Further, when the communication node B stops transmission, the wavelength λA at which light is emitted first is used as a reference.
This reference wavelength may be the last wavelength emitted, or may be the wavelength at which the wavelength shift in the group becomes the least, and is not limited to the above. Also,
In order to reduce the number of groups of wavelength trains, the wavelength trains may be focused on one group, and the present invention is not limited to the above example. In particular, when a wavelength shift occurs, the output of the moving communication node is “optical center node connection”.
Therefore, it is preferable to use a control method in which the wavelength arrangement is determined while predicting whether "all communication nodes can be connected" early.

In the present embodiment, high-density wavelength multiplexing can be realized without complicating the configuration of a communication node, and the number of channels of a wavelength multiplex communication system can be increased.

[Twelfth Embodiment] Hereinafter, a twelfth embodiment of the present invention will be described in detail with reference to the drawings. This embodiment relates to an optical center node different from the tenth embodiment in optical path connection means.

FIG. 19 is a configuration diagram of the optical center node according to the twelfth embodiment. The 1 × 2 optical switches 111 and 112 in FIG. 17 are replaced with four ON / OFF optical switches, two 1 × 2 optical couplers, and two optical fibers. The functions of the other blocks are the same as those described in the ninth embodiment, and a description thereof will not be repeated.

ON / OFF optical switches 1901, 190
Reference numerals 2, 1903, and 1904 denote one-input and one-output optical switches, which individually output optical signals input from the optical input ports to the optical output ports according to a control signal from the outside (here, the wavelength multiplexing communication control system 208). The state is switched between a state (ON state) and a state not outputting (OFF state). ON / OF
The optical output ports of the F optical switches 1901 and 1902 are (N
+1) × (N + 1) optical coupler 201. ON
The optical output ports of the / OFF optical switches 1903 and 1904 are connected to the N × 1 optical coupler 202. The connection states of the ON / OFF optical switches 1901 and 1903 are always reversed. That is, the ON / OFF optical switch 1901 is ON
In the state, the ON / OFF optical switch 1903 is OFF.
It is in a state. The same applies to the relationship between the ON / OFF optical switches 1902 and 1904.

Also, 1 × 2 optical couplers 1905 and 1906
Connects an optical signal input from one optical input port to two optical output ports. The 1 × 2 optical coupler 1905 distributes an optical signal from the optical input port 121 to an ON / OFF optical switch 1901 and an ON / OFF optical switch 1903. Similarly, the 1 × 2 optical coupler 1906 is connected to the optical input port 1
The optical signal from 22 is distributed to ON / OFF optical switches 1902 and 1904.

Further, the ON / OFF optical switch 190
1, 1902, 1903, 1904 and 1 × 2 optical coupler 1
By 905 and 1906, switching of the optical path in the optical center node similar to the tenth embodiment is performed. Communication node E
Specifically, the optical input port 121 to which is connected is as follows. (A) “Optical center node connection” state ON / OFF optical switch 1901 is OFF state, ON / OFF
The OFF light switch 1903 is in the ON state. As a result, the optical signal is transmitted from the communication node E to only the optical center node. (B) "All communication node connection" state ON / OFF optical switch 1901 is ON state, ON / O
The FF optical switch 1903 is in the OFF state. Thus, the optical signal from the communication node E is transmitted to the optical center node and all communication nodes in the network.

In this way, when the communication node E starts transmission, or when a failure occurs in the emission wavelength of the communication node, etc., the state is set to the "optical center node connection" state.
N / OFF optical switch 1901 is OFF, ON / O
The FF optical switch 1903 is turned on, and the communication node E
Is transmitted only to the optical center node, and when the transmission wavelength becomes a predetermined wavelength controlled by the wavelength division multiplexing communication control system 208, or when a certain interval from the wavelength of the adjacent node is reached, the "all communication" In this state, the communication node E starts transmitting transmission information. Thus, the normal state of “all communication nodes connected” is maintained.

As for the configuration of the optical center node, “optical center node connection” is set for each communication node.
Other configurations can be adopted as long as the switching between and "all communication node connections" can be performed independently.

In the ninth to twelfth embodiments,
The example in which the wavelength division multiplexing communication system control mechanism (particularly, the wavelength allocation detection system and the wavelength division multiplexing communication control system) is provided inside the optical center node has been described. I / O ports of
It is also possible to provide the wavelength control communication node connected thereto with a wavelength multiplexing communication control mechanism. In this case, the wavelength control communication node, if there is a communication node of the transmission request, until the emission wavelength of the communication node drops to a predetermined wavelength
It is necessary to stop the transmission wavelength of the communication node, but if the wavelength to be emitted first is set to the longest wavelength side, and it is determined that the wavelength is sequentially arranged at a constant wavelength interval Δλ from the longest wavelength to the short wavelength side, Transmit the emission wavelength of the communication node that requested transmission from the shortest wavelength, without stopping the transmission wavelength,
It is possible to sequentially move the wavelength to a wavelength having a wavelength interval Δλ with the adjacent node on the long wavelength side, and start information transmission at the wavelength. Other methods may be used for setting the wavelength arrangement.

Also, the connection of the optical path of the optical center node is
The "optical center node connection" is set only when the wavelength of the wavelength tunable optical transmitter is set, or when the wavelength tunable optical transmitter of the communication node goes out of control, but it is connected to the optical input port that is "optical center node connection". If the optical center node regenerates and relays the packet sent by the communication node, only after the wavelength setting of the wavelength tunable optical transmitter of the communication node is completed and before the transmission in the wavelength division multiplexing communication system is completed. It is also possible to set "all communication node connections".

With respect to the wavelength control method described in the eleventh embodiment, when setting the wavelength of the wavelength variable optical transmitter of the communication node, it is possible to use another procedure which can set the wavelength to the position of Δλ with the adjacent wavelength.

The star-type request-assigned wavelength-division multiplexing communication network as the background of the present invention employs a configuration in which the wavelength-division multiplexing communication system is in the 1.5 μm band and the packet communication system is in the 1.3 μm band. Other configurations can be used as long as the independence of the communication system is maintained. For example, an optical fiber or electric wire for packet communication may be separately laid as a packet communication system.

According to the ninth to twelfth embodiments described above,
The optical center node switches the optical path inside as described above, so that the wavelength setting of the wavelength tunable optical transmitter of the wavelength division multiplex communication system by the communication node can be performed without interference with the wavelength of another channel. .

Since the optical center node constantly monitors the wavelength allocation of the wavelength division multiplexing communication system, if there is a communication node in which the wavelength variable optical transmitter goes out of control, the optical center node detects it. , It is possible to prevent an optical signal from the communication node from being transmitted to another communication node.

Further, the optical center node can realize high-density wavelength multiplexing without complicating the configuration of the communication node by monitoring and controlling the wavelength arrangement of the wavelength multiplex communication system, and can reduce the number of channels of the wavelength multiplex communication system. You can do much.

As described in the present embodiment, by performing wavelength allocation detection at the center node where signals from the respective communication nodes are concentrated, optical path control can be performed without using additional communication means.

In each of the embodiments described above, the transmission wavelength of the tunable filter is controlled by the control circuit for detecting the wavelength arrangement or receiving the wavelength-division multiplexed signal, and the parameters for the control (for example, the voltage as in the above-described embodiment) are controlled. When the transmission wavelength is controlled by using the voltage, the wavelength transmitted by the tunable filter is recognized by the voltage). In the present invention, appropriate control parameters can be used depending on the type of the wavelength tunable filter (the fiber Fabry-Perot type used in the above embodiment, the semiconductor device, or the like). As a detection method, a so-called heterodyne detection method in which a wavelength is recognized as a frequency difference from the local oscillation light can be used. However, when the heterodyne detection method is adopted, the difference between the wavelength of the light to be detected and the wavelength of the local oscillation light can be recognized, but the magnitude relation cannot be recognized. Therefore, as described in each of the above embodiments, the transmission of the communication node is performed. In order to send to each communication node as wavelength control information which wavelength should be shifted to the long wavelength side or the short wavelength side, a configuration using a wavelength tunable filter as described in each of the above embodiments is more preferable. is there.

The network form of the present invention is not limited to the star type configuration, but may be a bus type, ring type, or the like. However, in the star-type configuration, the time until the wavelength control signal reaches each communication node after passing through the star coupler becomes almost constant if the optical path length difference between each communication node and the star coupler does not change significantly.
This is preferable because the wavelength control information reaches each communication node almost simultaneously.

[0198]

According to the present invention, any one of the network system (wavelength control node, non-receiving communication node,
The center node) performs wavelength allocation detection, generates a signal for wavelength control based on the detection, and sends out the signal to each communication node. Each communication node performs wavelength control based on the signal for wavelength control to cause interference. Communication can be performed without causing a problem. Also, high-density wavelength multiplexing can be realized. In particular, since the communication node does not need to separately have a wavelength selection (detection) means for detecting the wavelength arrangement and a wavelength selection (detection) means for receiving the wavelength-division multiplexed signal, it is possible to greatly reduce the network construction cost. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a wavelength division multiplexing communication system applied to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of an operation of a wavelength control method according to an embodiment of the present invention.

FIG. 3 is a diagram showing a data format of a wavelength control packet used in an embodiment of the present invention.

FIG. 4 is a configuration diagram of a wavelength control node according to an embodiment of the present invention.

FIG. 5 is a configuration diagram of a communication node applied to an embodiment of the present invention.

FIG. 6 is a diagram showing a wavelength arrangement of a wavelength division multiplexing communication system applied to the present invention and a conventional example.

FIG. 7 is a configuration diagram of a wavelength control node according to an embodiment of the present invention.

FIG. 8 is a configuration diagram of a wavelength division multiplexing communication system applied to the present invention.

FIG. 9 is a diagram showing an example of the operation of the wavelength control method according to an embodiment of the present invention.

FIG. 10 is a configuration diagram of a communication node applied to an embodiment of the present invention.

FIG. 11 is a diagram showing an example of the operation of the wavelength controller in the wavelength control system according to the embodiment of the present invention.

FIG. 12 is a configuration diagram of a wavelength division multiplexing communication system according to an embodiment of the present invention.

FIG. 13 is a diagram showing an example of the operation of the wavelength control method according to an embodiment of the present invention.

FIG. 14 is a diagram showing an example of the operation of the wavelength control method according to an embodiment of the present invention.

FIG. 15 is a configuration diagram of an embodiment of an optical center node according to the present invention.

FIG. 16 is a configuration diagram of a wavelength division multiplexing communication system according to an embodiment of the present invention.

FIG. 17 is a configuration diagram of an embodiment of an optical center node according to the present invention.

FIG. 18 is an explanatory diagram illustrating the operation of the wavelength control system of the optical center node according to the embodiment of the present invention;

FIG. 19 is a configuration diagram of an embodiment of an optical center node according to the present invention.

FIG. 20 is a configuration diagram of a wavelength division multiplexing communication system shown in a conventional example.

FIG. 21 is a diagram showing an example of an operation according to a conventional wavelength control method.

[Explanation of symbols]

33 Star couplers 31-31n Terminal stations 321-32n Communication nodes 341-34n, 351-35n Optical fibers 36, 361, 362 Wavelength control nodes 37, 38 Optical fibers 41, 51 Wavelength control systems 42, 53 Wavelength variable filters 43, 55 Wavelength variable filter driving circuits 44, 58 Light receiving element 45 Amplifier 46 Discriminator 47 LD 48 LD driving circuit 52 Wavelength variable LD 54 Wavelength variable LD driving circuit 56 Optical modulator 57 Optical modulator driving circuit 59, 511 Receiving circuit 510 Light receiving element 512 Optical multiplexer 513 Optical demultiplexer 71 Wavelength control system 101 Transmitter wavelength control system 102 Receiver wavelength control system 103 Optical splitter 201 (N + 1) × (N + 1) optical coupler 202 (N + 1) optical coupler 203 2 × 1 optical coupler 204 Optical demultiplexer 205 Wavelength allocation detection system 206 Optical receiver 207 Optical transmitter 208 Wavelength multiplex communication control system 271, 272, 281, 282 Optical fiber 1901, 1902, 1903, 1904 ON / OF
F optical switch

Claims (32)

[Claims] 1. A first communication system for performing wavelength multiplexing communication, a second communication system for performing communication independent of the first communication system,
A communication system having at least a plurality of communication nodes performing communication via the first communication system, comprising: detecting a wavelength arrangement in the first communication system; and transmitting a wavelength control signal based on the detected wavelength arrangement. A communication system, comprising: a wavelength control unit that transmits a signal to the plurality of communication nodes via the second communication system. 2. The communication system according to claim 1, wherein said wavelength control unit is a wavelength control node provided separately from said plurality of nodes. 3. The communication system according to claim 2, comprising a plurality of said wavelength control nodes. 4. The communication system according to claim 1, wherein the wavelength control unit is also used by a communication node of the plurality of communication nodes that is not receiving a signal via the first communication system. 5. Each of the plurality of communication nodes is connected to a center node via the first communication system and the second communication system, and the wavelength control unit is provided in the center node. The communication system according to claim 1. 6. The center node determines whether to distribute signals transmitted from each of the plurality of communication nodes via the first communication system to other communication nodes via the first communication system. The communication system according to claim 5, further comprising a selection unit that selects the one. 7. The communication system according to claim 1, wherein the wavelength control unit includes a tunable filter and a control circuit that controls a transmission wavelength of the tunable filter. 8. The communication system according to claim 1, wherein said communication node includes a wavelength tunable filter, and a control circuit for controlling a transmission wavelength of said wavelength tunable filter. 9. The system according to claim 1, wherein the first communication system and the second communication system are wavelength-division multiplexed.
The communication system according to any one of the above. 10. The communication node according to claim 9, wherein the communication node has a duplexer for separating the wavelength-multiplexed first communication system and the second communication system. Communications system. 11. The communication system according to claim 1, wherein said second communication system is a communication system for performing packet communication. 12. The communication system according to claim 1, wherein the plurality of communication nodes are connected to each other via distribution means for distributing a signal transmitted to the first communication system to another communication node. The communication system according to any one of the above. 13. A first communication system for performing wavelength division multiplexing communication,
In a communication system having a second communication system that performs communication independent of the first communication system and a plurality of communication nodes that perform communication via at least the first communication system, the plurality of communication nodes may be different from each other. A wavelength control method for controlling a wavelength of light to be output to the first communication system, wherein a wavelength controller in the communication system detects a wavelength arrangement in the first communication system, and the detected wavelength arrangement Transmitting a wavelength control signal based on the wavelength control signal to the plurality of communication nodes via the second communication system, wherein the plurality of communication nodes control a transmission wavelength based on the wavelength control signal. Method. 14. The wavelength control unit is a wavelength control node provided separately from the plurality of communication nodes, and the wavelength control node performs detection of the wavelength arrangement and transmission of a wavelength control signal. 3. The wavelength control method according to 1. 15. The communication system includes at least first and second wavelength control nodes as the wavelength control unit, wherein the transmission of the wavelength control signal is performed by the first wavelength control node. 14. The wavelength control method according to claim 13, wherein the second wavelength control node transmits the wavelength control signal when one wavelength control node stops transmitting the wavelength control signal. 16. The second wavelength control node according to claim 2, wherein:
Monitoring said wavelength control signal transmitted by said communication system, and said second wavelength control node transmits said wavelength control signal when said wavelength control signal has not been transmitted for a predetermined time. 16. The wavelength control method according to 15. 17. The communication system has at least first and second wavelength control nodes as the wavelength control unit, and the transmission of the wavelength control signal is performed by the first and second wavelength control nodes alternately. 2. The method according to claim 1, wherein
3. The wavelength control method according to 3. 18. The second wavelength control node according to claim 2, wherein
Monitoring the wavelength control signal transmitted in the communication system of, when the wavelength control signal transmitted by the first wavelength control node is not sent for a predetermined time,
16. The wavelength control method according to claim 15, wherein an interval for transmitting the wavelength control signal is shortened. 19. The communication system has at least first and second wavelength control nodes as the wavelength control unit, and when any one of the wavelength control nodes does not transmit the wavelength control signal. In a case where the wavelength control node that has not transmitted the wavelength control signal detects a control failure of the wavelength allocation in the first communication system, the wavelength control node that has not transmitted the wavelength control signal transmits 14. The wavelength control method according to claim 13, wherein a control signal is transmitted. 20. The wavelength control unit includes a communication node of the plurality of communication nodes that is not receiving a signal via the first communication system, and is configured as the wavelength control unit. 14. The wavelength control method according to claim 13, wherein the communication node detects the wavelength arrangement and transmits a wavelength control signal. 21. A communication node which is not receiving a signal via the first communication system, immediately before receiving a signal via the first communication system, or via the first communication system. 21. The wavelength control method according to claim 20, wherein the communication node in a state immediately after receiving the received signal becomes the wavelength control unit. 22. A communication node that has not received a signal via the first communication system has not received the next wavelength control signal for a predetermined time after receiving one wavelength control signal. 22. The wavelength control method according to claim 20, wherein the wavelength control unit transmits the wavelength control signal at the time. 23. A communication node in a state immediately before receiving a signal via the first communication system or immediately after receiving a signal via the first communication system, sends the wavelength control signal. The transmission interval of the wavelength control signal of
In a state other than the state immediately before receiving the signal via the first communication system or the state immediately after receiving the signal via the first communication system, and the signal via the first communication system 23. The wavelength control method according to claim 20, wherein a transmission interval of the wavelength control signal when the communication node in a non-receiving state transmits the wavelength control signal is shorter. 24. The wavelength control method according to claim 20, wherein the communication node serving as the wavelength control unit is specified by the communication node serving as the wavelength control unit. 25. Each of the plurality of communication nodes is connected to a center node via the first communication system and the second communication system, and the wavelength control unit is provided in the center node. 14. The wavelength control method according to claim 13, wherein the wavelength control signal transmitted by the wavelength control unit is transmitted from the center node to the plurality of communication nodes. 26. The center node, wherein a signal transmitted from each of the plurality of communication nodes via the first communication system is not distributed to another communication node until a predetermined wavelength is reached. 3. The wavelength control method according to 1. 27. The wavelength control method according to claim 13, wherein the wavelength control signal includes wavelength control information of all channels used in the first communication system. 28. The wavelength control signal, as information for controlling the wavelength of each channel, indicates that the wavelength of each channel is “maintained”, “move to a longer wavelength”, or “move to a shorter wavelength”. 28. The wavelength control method according to claim 27, comprising information. 29. The wavelength control method according to claim 27, wherein the wavelength control signal includes information indicating a channel not used in the first communication system. 30. The wavelength control method according to claim 29, wherein the communication node determines a channel to be used based on information indicating the unused channel included in the wavelength control signal. 31. The communication node according to claim 13, wherein the communication node is assigned a use channel in the first communication system by demand assignment control using the second communication system. The described wavelength control method. 32. The wavelength control signal includes information for controlling the wavelength of each channel such that the wavelength of each channel used in the first communication system has a predetermined wavelength interval. Claims 13 to 31
The wavelength control method according to any one of the above.