JPH10262030A - Supervisory control system in WDM optical transmission and terminal station thereof - Google Patents

Abstract

(57) [Summary] In WDM transmission, an SV signal can be transmitted to all repeaters with a small number of channels, and an optical fiber can be inspected by an OTDR method using an SV dedicated channel. An optical transmission system is provided. Hub stations A and B for transmitting and terminating an SV signal
By returning the SV signal output from the multiplexing / demultiplexing device 10 at the branch stations 1 and 2 connected by the optical multiplexer / demultiplexer 10, the path to the hub stations A and B is made one path. Also, by transmitting the SV signal back at the hub station B, the SV signal output from the hub station A can make a round of the route and return to the hub station A again. By returning the path of the SV signal so as to pass through all repeaters (not shown), only one channel for the SV signal may be used, and the degree of modulation due to branching does not deteriorate. It is possible to reliably receive the SV signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a supervisory control system in a WDM optical transmission system.

[0002]

2. Description of the Related Art Conventionally, in an optical communication system using an optical amplification repeater, in order to monitor and control the state (input / output power, temperature, etc.) of the repeater, a monitor control signal (hereinafter, referred to as SV) is transmitted from a terminal station to the repeater. Signal). As a transmission method, in the case of one-channel communication (one-wave transmission), a method of amplitude-modulating an SV signal into a main signal is used. Upon receiving the SV signal, the repeater directly modulates its own state as a response signal on the excitation LD and sends it back to the terminal.

FIG. 7 is a diagram schematically showing a configuration of a one-wave transmission optical communication system and a method of modulating an SV signal. FIG. 7A is a diagram showing a state in which the SV signal is superimposed on the main signal.

[0004] As shown in FIG. (A), SV signal amplitude V ₂ in the form of amplitude modulation (SV command modulation signal) is superimposed on the main signal amplitude V _1. This is because, in the case of one-wave transmission, since there is only one channel, S
When a V signal is to be transmitted, such a method has been adopted because the SV signal needs to be transmitted together with the main signal in one channel. Here, V ₂ /
V ₁ × 100 (%) is referred to as the SV signal modulation degree.

FIG. 1B is a schematic configuration diagram of a one-wave transmission system. In the case of one-wave transmission, basically, the communication mode is between only two terminal stations. That is, since only one channel is provided because the number of channels is one, the destination of information sent using one line is limited to one. Thus, in the case of one-wave transmission, one set of terminal stations 6
Between 0 and 61, an up line and a down line are provided. In particular, in the case of long-distance communication such as undersea communication, optical amplification repeaters 62-1, 62-2,.
-1, 62-n. Each optical amplification repeater 62-
1, 62-2, ..., 62-n-1, 62-n,
The weakened optical signal transmitted is amplified and sent to the next repeater.

[0006] In such a system, the SV signal is transmitted by being superimposed on the main signal. Optical amplification repeater 62-
1, 62-2, ..., 62-n-1, 62-n
A unique number determined by the terminal station is assigned, and when the SV signal is transmitted from the terminal station, this number is set as data. When each repeater receives the SV signal, it obtains the number contained in the SV signal and determines whether or not it matches the number assigned to its own repeater.

If the number does not match the number of the own repeater, the optical amplification repeaters 62-1, 62-2,..., 62-n
-1, 62-n do nothing and relay the optical signal including the SV signal as it is. If the repeater number matches the own repeater number, the monitor control command included in the SV signal is acquired, the state of the repeater is acquired according to the command, and the signal is obtained. Send to the station.

[0008] On the other hand, developments have recently been made with the aim of realizing wavelength division multiplexing communication, and it is considered that future optical communication networks will employ wavelength division multiplexing (WDM). In the case of WDM transmission, since a plurality of channels can be transmitted by one fiber, a plurality of terminal stations can be connected by branching / combining optical signals.

In one-wave transmission, when transmitting an SV signal,
Although the amplitude modulation method was used, W
In the case of DM transmission, it is difficult to perform monitoring control with the above method for the following reasons. (1) Due to the lack of the main signal channel in which the SV signal is amplitude-modulated by the optical multiplexing / demultiplexing, the modulation degree of the SV signal becomes small and the repeater cannot receive. (2) When multi-relay transmission is performed, the ratio of the signal light power to the total optical power is reduced due to accumulation of noise light, so that the degree of modulation of the SV signal superimposed on the signal light is naturally reduced. (3) The propagation time of the signal light varies depending on the wavelength due to the chromatic dispersion of the fiber. Therefore, the SV superimposed on each signal light
A phase shift also occurs in the signal, which reduces the degree of modulation. (4) If the degree of modulation transmitted from the terminal station is increased in consideration of the degree of modulation that decreases in (1), (2), and (3), the modulation of the SV signal affects the main signal.

FIG. 8 is a diagram showing a schematic diagram of a WDM transmission system and a conceptual diagram of an OTDR path in an optical repeater. As shown in FIG. 7A, in the case of WDM transmission,
Optical multiplexer / demultiplexers 70 and 71 are connected in the middle of a communication line formed by optical fibers, and two or more terminal stations are connected. Two optical fibers, an up line and a down line, are provided as in the case of one-wave transmission. For example, in a signal transmitted from the terminal station A, a plurality of pieces of information are transmitted in one optical fiber using a plurality of channels. The optical multiplexing / demultiplexing devices 70 and 71 multiplex or split all the transmitted lights.

The signal transmitted from the terminal station A to the terminal station B is split by the optical multiplexer / demultiplexer 70 and reaches the terminal station B via the optical repeater. The signal transmitted from the terminal station A to the terminal station C is split by the optical multiplexer / demultiplexer 71 and reaches the terminal station C via the optical repeater.
The signal transmitted from the terminal station A to the terminal station D is not branched by any optical multiplexer / demultiplexer, and reaches the terminal station D via the repeater.

FIG. 1B shows a conventional method for transmitting an SV signal in WDM transmission. In the case of WDM transmission, when the SV signal is superimposed on the main signal as in the case of one-wave transmission, the modulation degree of the SV signal decreases along with the deterioration of the main signal, and it is difficult to detect at each repeater. turn into. Therefore, in the case of WDM transmission, a dedicated channel for transmitting the SV signal is prepared, and the SV signal is transmitted on this channel. By doing so, even if the optical signal is split by the optical multiplexer / demultiplexer, the SV signal is also split, so that there is no need to worry about deterioration of the modulation factor.

FIG. 1B is a diagram specifically showing a method of transmitting an SV signal. In order to transmit the SV signal to all of the repeaters connected by the optical multiplexer / demultiplexer, if the SV signal is to be transmitted from the terminal station A, the SV signal is transmitted through the communication path to each of the terminal stations B, C, and D. I have to pass.
However, if the SV signal is transmitted on one channel, the SV signal must be split by the optical multiplexing / demultiplexing device, so that the power of the SV signal itself becomes weak, and the signal may not be detected by the repeater. There is.

Therefore, SV signal channels are prepared by the number of terminal stations connected to the terminal station A, and the SV signal of each channel is transmitted to each terminal station.
For example, as shown in FIG. 3B, the SV signal transmitted on the channel W1 is transmitted to the terminal D, the SV signal transmitted on the channel W2 is transmitted to the terminal C, and the SV signal transmitted on the channel W3 is transmitted to the terminal D. A channel dedicated to transmission to each terminal station, such as to station B, is provided.

By doing so, the SV of one channel
Since there is no need to split the signal, there is no fear that the power of the SV signal drops and the repeater cannot receive the signal. However, since the number of channels is required by the number of terminals connected to the terminal A, when a large number of terminals are connected,
Many channels must be dedicated for SV signals,
Valuable communication bandwidth may be wasted.

FIG. 1C shows an OTDR (optical time d).
The route used for the omain refrectometer is conceptually shown. The OTDR method is used to check the state of optical fiber damage or optical loss. In the OTDR method, an optical signal is sent from one optical fiber and an optical signal sent from the other optical fiber is received. Must-have.
Therefore, an OTDR path connecting the uplink and the downlink is formed in the optical amplifier provided in the repeater. This path simply branches the optical fiber and connects the upstream line and the downstream line. OTD
When inspecting the characteristics of an optical fiber using the R method,
The output of the main signal and other signals is stopped, and the inspection by the OTDR method is performed. Then, the optical signal transmitted from the uplink is returned in each repeater and returns to the original terminal station via the downlink. By detecting the returned optical signal, the optical fiber can be inspected.

[0017]

As described above, WD
In M transmission, when trying to transmit an SV signal to each repeater, the number of channels required is equal to the number of terminals connected to the terminal outputting the SV signal. I will.

Further, in order to transmit an SV signal through one channel in order not to waste the band, as described above, when the light is split by the optical multiplexer / demultiplexer, the S
Since the power of the V signal is weakened, the SV signal may not be received by the repeater.

Therefore, an object of the present invention is to provide a system capable of transmitting an SV signal to all repeaters with a small number of channels in WDM transmission, and using an SV dedicated channel for OT.
An object of the present invention is to provide an optical transmission system capable of inspecting an optical fiber by the DR method.

[0020]

SUMMARY OF THE INVENTION A supervisory control system for WDM transmission according to the present invention comprises a hub station which is a terminal station for transmitting and terminating an SV signal, a branch station which is a terminal station for returning an SV signal and transmitting the optical signal. It is assumed that a repeater for relaying a signal is connected to an optical transmission line. And SV
The SV signal is transmitted from the hub station using the signal dedicated channel, and the SV signal is transmitted back at the branch station so that the SV signal passes through all the repeaters connected to the system. It is characterized by forming a simple path.

Further, the terminal station used in the system of the present invention has at least a switch for switching an optical path and a repeater monitoring device for generating an SV signal. The terminal station returns the SV signal, and transmits or terminates the SV signal. When the switch is switched, the transmission path is switched, and when the SV signal is transmitted, the SV generated by the repeater monitoring device is used.
The signal is converted into an optical signal and transmitted.

According to such a system or terminal of the present invention, the SV signal does not have to be branched and transmitted to each terminal. Instead, the entire optical path of the SV signal is changed and transmitted to the terminal. Turns back and forms a path through all repeaters connected to the system,
There is no need to worry about degradation of the SV signal due to branching, and there is no need to transmit the SV signal using the same number of channels as the number of terminal stations.

In particular, according to the present invention, an SV signal can be transmitted if there is at least one channel. Therefore,
Many channels are occupied for the SV signal, and many channels can be used for transmitting the main signal without narrowing the transmission band.

Further, since the terminal station according to the present invention can return or transmit an SV signal, any terminal station can be a hub station and a branch station. Therefore, S
An appropriate SV signal transmission path can be formed depending on the position of the repeater to which the V signal is to be delivered.

[0025]

FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 1A shows the first embodiment, and shows a configuration of four terminal stations. That is, the hub stations A and B and the branch stations 1 and 2 correspond to each terminal station. In the present invention, a single channel for SV signal transmission is used, the SV signal is looped back at each branch station, and a communication path is connected to a hub station that is the SV signal transmitting station.

That is, the SV signal output from the hub station A is not terminated at the branch stations 1 and 2, but is turned
It is terminated at the hub station B which is also the transmitting station of the V signal. Also,
The SV signal output from the hub station B is looped back at the branch stations 1 and 2 and terminated at the hub station A. When the SV signals are transmitted from the hub stations A and B, they are bent by the optical multiplexing / demultiplexing device 10 and travel to the branch stations 1 and 2.

A plurality of repeaters (not shown) are provided between the hub stations A and B, the branch stations 1 and 2, and the optical multiplexer / demultiplexer 10, and the SV signal passes through all these repeaters. Become. Therefore, the SV signal is turned back without terminating at each terminal station, a path is formed so as to pass through all the repeaters, and terminated at an appropriate terminal station. Can be transmitted in the connected system. One channel may be used because only one set of the hub station A as the transmitting station and the hub station B as the receiving station exists in the system. Therefore, since there is no need to split the SV signal, channels are not required for the number of terminal stations,
There is no wasted bandwidth.

The hub stations A and B send and terminate the SV signal. The response signal from the repeater is superimposed on the main signal, transmitted on the main line, and received by the terminal connected to the repeater that transmitted the response signal via the main line. Therefore, the terminal station has a function of acquiring the state (input / output state, temperature, etc.) of the repeater regardless of whether it is a hub station or a branch station.

FIG. 2B shows an example of the configuration of an optical multiplexer / demultiplexer. As shown in FIG. 1, the optical multiplexing / demultiplexing device 10 includes branching modules 11-1 and 11-2 and a multiplexing module 12
-1, 12-2. Branch module 11-
The optical signal input to 1 is split and split into a line in the linear direction containing only the main signal and a line containing the SV signal and going to the branch station. The optical signal input to the branch module 11-2 is also divided into a line including the SV signal and going to the branch station and a line only including the main signal. The multiplexing module 12-1 receives the optical signal of the line including only the main signal from the branch module 11-1 and the optical signal including the SV signal returned from the branch station, and multiplexes the signals to the hub station. Send. Similarly, the multiplexing module 12-2 is connected to a line including only the main signal from the branching module 11-2 and a line including the SV signal from the branch station. Send out.

FIG. 3C shows another embodiment of the present invention. In the configuration shown in FIG. 3C, the hub station B does not terminate the SV signal but loops back like a branch station. FIG. 1A shows a configuration in which two hub stations are provided for easy understanding. However, basically, the present invention can perform its function if one hub station is provided.

That is, since the transmitting station and the receiving station of the SV signal are the same, it is the same as providing only one set of the transmitting and receiving of the SV signal. Since it is turned back at each branch station and hub station B, it can pass through all the repeaters (not shown) provided in the system.

Thus, the source of the SV signal and the SV
By providing a signal return path, each terminal station can be used as a hub station,
It can also be used as a branch station. Therefore, each terminal station can be sequentially switched and used as a hub station.

The SV signal is not always transmitted, and is output only when necessary. By the way, S
Since the V signal is transmitted after being wavelength-division multiplexed with the main signal,
When the SV signal is not transmitted, it is conceivable that the optical output of the entire optical signal changes depending on whether the SV signal is transmitted only as the main signal and the transmission characteristic changes. . Therefore, when the SV signal is not transmitted, a pseudo signal having the same output as that of the SV signal is transmitted, and the output of the entire optical signal is made constant. By doing so, it is possible to prevent the transmission characteristics from deteriorating due to the change in the optical output.

As described above, according to the present invention, the SV signal is looped back at the terminal, so that it is not necessary to split the SV signal. An SV signal can be sent. Therefore, only one channel is required for transmitting the SV signal, and the communication band is not wasted by using many channels for the SV signal.

In addition, since the path of the SV signal is configured to pass through all the terminal stations and the repeaters as in the present invention, when the optical fiber is inspected by using the OTDR method, the SV signal wavelength The inspection can be performed for all the routes by using. Therefore, OTD
Since only one terminal station needs to transmit an optical signal based on the R method, the optical fiber system can be easily inspected by the OTDR method.

FIG. 2 is a diagram showing a configuration example of the multiplexing module and the branch module. The optical signal input from the input is output to the fiber grating 21-1 by the circulator 22-1. In the fiber grating 21-1, the optical signal of the wavelength (drop wavelength) at which the line is to be switched (the drop wavelength) and the wavelength of the SV signal are reflected, input again to the circulator 22-1, and output in the direction of DROP. Light having a wavelength other than the drop wavelength and the SV wavelength passes through the fiber grating 21-1 as it is, passes through the isolator 20, and
Is input to

The optical signal directly coming from the branch module 11 passes through the fiber grating 21-2 as it is,
The signal passes through the circulator 22-2 and is transmitted to the output side. On the other hand, the SV signal and main signal coming from the branch station are input to the multiplexing module 12 from the ADD side, and input to the fiber grating 21-2 by the circulator 22-2. Fiber grating 21
In -2, the wavelength (add wavelength) of the main signal to be multiplexed with the wavelength of the SV signal is reflected, and again the circulator 22-
2 is input.

The reason why the isolator 20 is provided between the branch module 11 and the multiplexing module 12 is as follows.
The optical signal coming from D is a fiber grating 21-2.
This is to prevent a part of this optical signal from propagating in the line in the opposite direction when a part of the optical signal passes without being completely reflected.

In this way, the SV signal and part of the main signal coming from the input are output in the direction of DROP and transmitted to the branch station. The SV signal and the main signal coming from the branch station enter the multiplexing module 12 from the direction of ADD, are multiplexed with the optical signal coming directly from the branching module 11, and transmitted to the output. In the direction of output, FIG.
, Or a hub station B shown in FIG. 1C that functions as a branch station that returns an SV signal.

The configurations of the branch module 11 and the multiplexing module 12 shown in FIG. 2 are merely examples, and do not necessarily have to be such configurations. FIG. 3 is a diagram showing a configuration example for transmitting and returning an SV signal in a terminal station.

FIG. 5A shows an example of a configuration (1R configuration) in which an SV signal is folded back as an optical signal. The SV signal input from the input side passes through the band-pass filter 25 to remove noise and the like, and is sent to the optical amplifier 26. The optical amplifier 26 amplifies the SV signal as it is.
By closing the optical switch 27, the optical amplifier 26
The SV signal is output to the output side as it is, and is looped back at the terminal station (branch station).

On the other hand, by keeping the optical switch 27 open, the repeater monitoring device 29 issues an SV command and
An SV signal of the optical signal is generated by the signal transmitter 28,
The light is output to the output side through the optical switch 27. At this time, the repeater monitoring device 29 opens the optical switch 27 using the control line 30.

By having such a configuration, 1
One terminal station can be a branch station that simply returns the SV signal, or a hub station that transmits the SV signal.

FIG. 3B shows an example of a configuration (2R configuration) in which the waveform of the SV signal is shaped and turned back. From the optical signal input from the input side, only the SV signal is extracted by the band-pass filter 25 and converted into an electric signal by the photodiode 31. The identification circuit 32 is provided with an analog switch. When this switch is closed, the signal from the photodiode 31 is received, the signal is shaped, and then transmitted to the SV signal transmitter 33. The SV signal transmitter 33 converts the electric signal into an optical signal and outputs it to the output side. Thereby, the function as the branch station having the 2R configuration can be achieved.

When the analog switch in the identification circuit 32 is open, the SV command signal (electric signal) from the repeater monitor 29 is input to the identification circuit 32 and transmitted to the SV signal transmitter 33. . The SV signal transmitter 33 converts the electric signal into an optical signal as described above and outputs the optical signal to the output side. Thus, the function as a hub station can be achieved.

FIG. 3C shows an example of a configuration (3R configuration) in which the SV signal is synchronized and looped back. From the optical signal input from the input, only the SV signal is extracted by the band pass filter 25. The extracted SV signal is converted into an electric signal by the photodiode 31. This electric signal is sent to the discrimination circuit 32, and a negative feedback is applied between the photodiode 31 and the discrimination circuit 32 by the PLL circuit 34. To the SV signal transmitter 33.
As a result, the SV signal is adjusted in phase in addition to the waveform deteriorated by being transmitted, so that the SV signal transmitter 3
The signal is converted into an optical signal at 3 and output.

When the terminal station is a hub station, as described above, the analog switch in the identification circuit 32 is opened, and the SV signal transmitter 3 receives the signal from the repeater monitor 29.
In step 3, the signal is converted into an optical signal and transmitted.

FIG. 4 shows a configuration for receiving a response signal at the terminal station. The configuration for receiving the response signal includes an optical amplifier 35, a photodiode 36, an electric amplifier 37, a low-pass filter 38, and a frequency counter 39, as shown in FIG. The optical signal input from the transmission line is weakened because it has propagated through the transmission line, and is amplified by the optical amplifier 35. The optical signal amplified by the optical amplifier 35 is converted into an electric signal by the photodiode 36 and further amplified by the electric amplifier 37.

In practice, a circuit for extracting the main signal is provided in this stage in parallel with a circuit for extracting the response signal. However, in order to mainly explain the configuration for receiving the response signal, the circuit is illustrated in FIG. It has not been. That is, since the response signal is superimposed on the main signal, up to this stage, the entire signal including the response signal is handled.

The signal amplified by the electric amplifier 37 is passed through a low-pass filter 38 to extract only a response signal. The cutoff frequency of the low-pass filter is, for example, several tens of kHz. By passing through the low-pass filter 38, main signal components, noise, and the like are removed. The frequency of the response signal extracted by the low-pass filter 38 is measured by a frequency counter 39.

The terminal station (the station that receives the response signal irrespective of the branch station or the hub station) previously stores a correspondence table between the frequency of the response signal and the monitor value of each state of the repeater. The state of the repeater that has returned the response signal can be known from the frequency of the response signal obtained as described above.

FIG. 5 shows an example of a structure for receiving an SV signal and transmitting a response signal in the repeater. The uplink and the downlink are connected to the repeater.
A V receiving circuit and a response signal transmitting circuit are provided.

The optical signal input from the repeater input passes through the couplers 40-1 and 40-4, and becomes erbium-doped.
It is amplified by the fiber amplifiers 46-1 and 46-2. The amplified optical signal is branched by couplers 40-2 and 40-5, converted into electric signals by photodiodes 42-1 and 42-2, and converted into electric signals by electric amplifiers 47-1 and 45-2.
7-2. The electric signals amplified by the electric amplifiers 47-1 and 47-2 are output from a laser diode 41-.
1 and 41-2, and are multiplexed with the input light by couplers 40-1 and 40-4. Thus, the couplers 40-1, 4
0-2, 40-4, 40-5 photodiode 42-
1, 42-2, electric amplifiers 47-1, 47-2, and laser diodes 41-1 and 41-2 pass through erbium-doped fiber amplifiers 46-1 and 46-2.
Negative feedback to the coupler 40-2,
Adjustment is made so that the optical signal output from 40-5 has a constant output.

The optical signals output from the couplers 40-2 and 40-5 are branched by the couplers 40-3 and 40-6.
The wavelength of the SV signal is extracted by the optical filters 43-1 and 43-2. The extracted SV signal is output from the photodiode 42-
3, 42-4, are converted into electric signals and further passed through narrow-band electric filters 44-1 and 44-2 to remove noise.

The SV signals extracted in this way are received as electric signals by the SV receiving circuits 45-1 and 45-2. For the SV signals 45-1 and 45-2, the repeater number included in the SV signal is extracted. If the repeater number is the own repeater number, the SV command included in the SV signal is extracted. Acquire the status of the repeater according to the command and generate a response signal. The generated response signal is converted into an optical signal by the laser diodes 41-1 and 41-2, and is superimposed on the main signal and transmitted. The response signal can be exchanged between the SV receiving circuits 45-1 and 45-2.
From 1 and 45-2, a response signal can be transmitted to both the uplink and the downlink.

In particular, the SV signal extracted by the optical filters 43-1 and 43-2 is transmitted on a channel different from the main signal, but the response signal output from the SV receiving circuit is a laser diode 41-1. , 41-2, is converted to an optical signal, superimposed on the main signal, and sent to the repeater output.

In the same figure, an example of a 1R type repeater using an erbium-doped fiber amplifier is shown. This part is a 2R system which once converts an optical signal into an electric signal, shapes the waveform, and sends out the signal. The method may be a 3R method that uses phase matching in addition to waveform shaping.

FIG. 6 is a schematic configuration diagram of the SV receiving circuit of FIG. The SV receiving circuit is an electric circuit, and the amplifier 5
0, a demodulation circuit 51, an interface circuit 52, an SV signal identification circuit 53, and a response signal generator 54.

[0059] The SV signal input to the SV receiving circuit shown in the figure is amplified by the amplifier 50 and sent to the demodulation circuit 51. The SV signal demodulated by the demodulation circuit 51 is sent to the interface circuit 52 and is also sent to the demodulation circuit of the SV receiving circuit on the opposite line side, and is used as a signal demodulated by the demodulation circuit on the opposite line side. The pair line is a downlink for the uplink and an uplink for the downlink. Therefore, if the SV receiving circuit shown in the figure is provided on the upstream side, the corresponding circuit in the SV receiving circuit on the downstream side is provided, and the corresponding circuit is provided on the downstream side. If so, it refers to the corresponding circuit on the uplink.

The interface circuit 52 is a demodulation circuit 51
This is a circuit for extracting information included in the SV signal from the SV signal sent from the SMC. That is, although the SV signal includes a repeater number, a monitoring control command, and the like, it is extracted according to a predetermined format. Further, the repeater number and the monitoring control command of the SV signal received on the opposite line side are also sent to the interface circuit 52 and sent to the next SV signal identification circuit 53. The SV signal identification circuit 53 determines whether the repeater number included in the SV signal is that of the own repeater. If the signal is not the one of the own repeater, no signal is sent to the next stage, and the signal is terminated by this circuit.
The SV signal not branched in 0-3 and 40-6 is transmitted to the next repeater.

Assuming that the repeater number of the own repeater has been set in the SV signal identification circuit 53, the monitor control command is interpreted and the state of the own repeater is obtained. Then, a signal indicating the state of the repeater is sent to the response signal generator 54,
A signal having a frequency indicating the state of the repeater is generated and output to an LD drive circuit including a laser diode (LD).
The response signal generating unit 54 also exchanges signals with the line response signal generating unit so that the same response signal is generated in the uplink and the downlink.

[0062]

According to the configuration, the SV signal is turned back at the terminal station, and the SV signal is returned to the terminal station branched by the optical multiplexer / demultiplexer, so that many terminal stations are connected by the optical multiplexer / demultiplexer. , Only one channel is required to send the SV signal.
The communication band can be used effectively without occupying many channels for transmitting the V signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a multiplexing module and a branch module.

FIG. 3 is a diagram illustrating a configuration example for transmitting and returning an SV signal in a terminal station.

FIG. 4 shows a configuration for receiving a response signal at a terminal station.

FIG. 5 is a configuration example for receiving an SV signal and transmitting a response signal in a repeater.

FIG. 6 is a schematic configuration diagram of an SV receiving circuit in FIG. 5;

FIG. 7 is a diagram schematically illustrating a configuration of a one-wave transmission optical communication system and a method of modulating an SV signal.

FIG. 8 is a diagram showing a schematic diagram of a WDM transmission system and a conceptual diagram of an OTDR path in an optical repeater.

[Explanation of symbols]

10, 70, 71 Optical multiplexer / demultiplexer 11, 11-1, 11-2 Branch module 12, 12-1, 12-2 Multiplexing module 20 Isolator 21-1, 21-2 Fiber grating 22-1, 22-2 Circulator 25 band-pass filter 26, 35 optical amplifier 27 optical switch 28, 33 SV signal transmitter 29 repeater monitoring device 30 control line 31, 36, 42-1 to 42-4 photodiode 32 identification circuit 34 PLL circuit 37, 47 -1, 47-2 Electric amplifier 38 Low-pass filter 39 Frequency counter 40-1 to 40-6 Coupler 41-1 and 41-2 Laser diode 43-1 and 43-2 Optical filter 44-1 and 44-2 Narrow band filter 45-1, 45-2 SV receiving circuit 46-1, 46-2 Erbium-doped filter Driver amplifier 50 amplifier 51 demodulator circuit 52 interface circuit 53 SV signal identification circuit 54 the response signal generation unit 60 and 61 terminal stations 62-1 to 62-n optical amplifying repeater

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/14 10/135 10/13 10/12

Claims (12)

[Claims] 1. An optical transmission line connects a hub station which is a terminal station for transmitting and terminating an SV signal, a branch station which is a terminal station for returning and transmitting an SV signal, and a repeater for relaying an optical signal. A supervisory control system for WDM transmission, wherein the SV signal is transmitted from the hub station using an SV signal dedicated channel, and the SV signal is transmitted back at the branch station, whereby the SV signal is connected to the system. A monitoring and control system in WDM transmission, wherein a path is formed so as to pass through all the repeaters. 2. The supervisory control system in WDM transmission according to claim 1, wherein said SV signal is turned back by said branch station by using an optical amplifier to return the SV signal as it is. 3. The supervisory control system in WDM transmission according to claim 1, wherein the SV signal is turned back at the branch station by using a 2R method in which an optical signal is converted into an electric signal, reproduced, and turned back. . 4. The method according to claim 1, wherein the SV signal is turned back at the branch station by using a 3R method in which an optical signal is converted into an electric signal, phase-matched, reproduced, and turned back. A supervisory control system for WDM transmission. 5. The WD according to claim 1, wherein the SV signal is transmitted using one dedicated channel.
Supervisory control system for M transmission. 6. The monitoring and control system according to claim 5, wherein the repeater receives the SV signal using an optical filter for a dedicated channel for the SV signal. 7. An O / O switch using a channel dedicated to the SV signal.
2. The supervisory control system for WDM transmission according to claim 1, wherein the optical transmission path is inspected by the TDR method. 8. An end station for transmitting, terminating, or returning transmission of an SV signal in WDM transmission, comprising at least a switch for switching an optical path and a repeater monitoring device for generating an SV signal. The transmission path is switched by switching the switch between the case of returning transmission and the case of transmitting or terminating the SV signal, and when transmitting the SV signal, the SV signal generated by the repeater monitoring device is converted into an optical signal. A terminal station characterized by being converted and transmitted. 9. The terminal station according to claim 8, wherein, as a method of returning the SV signal, the optical signal is returned as it is using an optical amplifier. 10. A method of transmitting the SV signal back, wherein the optical signal is converted into an electric signal, reproduced, and returned.
9. The terminal according to claim 8, wherein a method is used. 11. The terminal station according to claim 8, wherein the method of transmitting the SV signal back is a 3R system in which an optical signal is converted into an electric signal, reproduced with phase matching, and then returned. . 12. The terminal according to claim 8, wherein said SV signal is transmitted using one dedicated channel.