JPH02104149A - Optical atm exchange system - Google Patents

Abstract

PURPOSE:To allow the title system to correspond also to the acceleration or capacity increment of information by multiplexing wavelengths having routing information and executing switching by self-routing on the basis of the multiplexed wavelength. CONSTITUTION:A wavelength multiplex part 1-I (I=1 to N) multiplexes an input optical signal with a required wavelength having input information into wavelength having routing information in a communication line. Then, a switch part 2-I in a self routing switch S executes switching based upon self-routing and outputs the input information to a required output terminal. At the time of generating collision in information obtained from respective input terminals, the input information is temporarily stored in a buffer part 3-I to evade the collision of respective information. Consequently, the system can be allowed to sufficiently correspond to the acceleration or capacity increment of information.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology (Fig. 13) Means for solving the problem to be solved by the invention (Fig. 1) Effect (Fig. 1) ) Embodiment (Figs. 1 to 12) Effects of the invention [Summary] Optical signals are transmitted as they are in the asynchronous transfer mode (A, TM; Asy
Regarding the optical ATM switching system, which exchanges information using the chronous transfer mode (Nchronous Transfer Mode), the purpose of this system is to enable information to be exchanged using the ATM method in the form of light, i.e., asynchronously, and to be able to fully support high-speed and large-capacity information. , a wavelength multiplexing unit that multiplexes a wavelength having routing information within a communication path onto an input optical signal having a desired wavelength having input information; and a wavelength multiplexing unit that multiplexes a wavelength having routing information within the communication path onto an input optical signal having a desired wavelength having input information; It is equipped with a switch section for outputting information to a terminal, and a buffer section for avoiding collision of information from each input terminal for each output terminal.A wavelength multiplexing section multiplexes wavelengths with routing information, and based on this wavelength, By performing switching through routing, input information is configured to be output to a desired output terminal.

[Industrial Field of Application] The present invention enables optical signals to be transmitted in an asynchronous transfer mode (ATM) as they are.
) relates to an optical ATM switching system.

It is desired that a wideband I5DN can efficiently and flexibly provide a wide variety of services, such as audio at 64 Mbps to video signals at 150 Mbps or more.

ATM replaces traditional circuit switching and packet switching methods.
It is attracting attention as a new method that meets these demands, and research is being actively conducted at various institutions.

In addition, in recent years, research has been progressing on optical exchange, which utilizes the high speed and broadband properties of light to exchange optical information as is, as a means of realizing a wideband 15DN exchange system.

[Prior Art] FIG. 13 is a block diagram showing a conventional optical switching system. In this FIG. For example, an optical memory is used to change the time position of data.

103 is an optical space switch; this optical space switch 103
This is to replace the spatial position of data, and for example, an optical switch is used.

With such a configuration, data input to a certain incoming line has its time position swapped in time slot units by the optical time switch 101, and its spatial position is swapped by the optical space switch 103. 102, the time positions are switched in units of time slots, and the signals are output from the required outgoing line.

[Problem A to be Solved by the Invention] However, with such conventional means, it is necessary to achieve time synchronization.
When the time length and severity increase and high-speed switching is required, there is a problem that it is not possible to adequately meet this demand.

The present invention was made in view of these problems, and
It is an object of the present invention to provide an optical ATM exchange system which allows information to be exchanged in the form of light using the ATM system, that is, asynchronously, and which can sufficiently cope with higher speeds and larger volumes of information.

[Means to solve the problem] FIG. 1 is a block diagram of the principle of the present invention.

In this FIG. 1, 1-1. ..., 1-N is a wavelength multiplexing section, and this wavelength multiplexing section 1-I (I=1゜2, .
, N) is for multiplexing a wavelength having routing information within a communication path onto an input optical signal of a required wavelength having input information.

S is a self-routing switch, and this self-routing switch S is connected to the switch section 2-1. Buffer part 3-I
and a multiplexing switch section 4-I.

Here, the switch section 2-I outputs input information to a desired output terminal based on the wavelength having the routing information multiplexed by the wavelength multiplexing section 1-2.

Further, the buffer section 3-I avoids collision of information from each input terminal for each output terminal, and each buffer section 3-I
has a plurality (N) of buffers 3-11, . . . , 3-IN.

Further, the multiplexing switch section 4-I is configured to control each buffer 3-I.
It combines optical signals from J (J=1.2. . . , N).

[Function] With such a configuration, the wavelength multiplexing section 1-I multiplexes the wavelength having the routing information within the communication path onto the input optical signal of the required wavelength having the input information. Thereafter, the switch unit 2-I of the self-routing switch S performs switching by self-routing based on the wavelength, thereby transmitting the input information to a desired output terminal.

If a conflict occurs between the information from each input terminal, the input information is temporarily stored in the buffer section 3-I,
Collisions are to be avoided.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is an overall block diagram showing an embodiment of the present invention, and in this FIG. 2, 1-1.1-2. ..., 1-9
is a VCI conversion unit that also functions as a wavelength multiplexing unit,
, m(7) VCI converter 1-I (I=1°2,...
9) receives a signal from the call processing unit CP, which will be described later, for each input call [user information of this input call is carried using a type of packet called a cell on the transmission link; , a fixed-length user information field and an information identifier (VCI; Virtual Channel Iden).
a fixed-length header containing a fixed-length header containing a fixed-length header containing a fixed-length header containing a fixed-length header containing the input information. wavelength λX that has routing information within one communication path for the input optical signal (input call)
,λ■.

λ2 is multiplexed.

In this embodiment, as will be described later, there is a three-stage node group configuration, and the wavelength λX determines the routing TAG1 in the first stage node group, and the wavelength λV determines the routing TAG1 in the second stage node group. The routing TAG2 is determined, and the wavelength λZ is the third
Determine the routing TAG3 in the node group of the stage.

Here, the allocation of the wavelengths λX, λV, and λ2 is shown in FIG. 6. As can be seen from FIG. 6, wavelengths λX, λV, and λ2 are assigned to be different wavelengths for wavelength multiplexing. Further, each wavelength is arranged at equal intervals corresponding to the number of output ports in the node (nine in this example). Note that in FIG. 6, the numbers in (1) to (3) are output port numbers in each node, and the numbers 1 to 9 below them indicate wavelength values. Therefore, the wavelength λX is one of λ1 to λ, the wavelength λV is one of λ, to λ6, and the wavelength λ2 is one of λ, to λ.

Furthermore, in FIG. 2, SP is a signal processing unit, CP is a call processing unit, and the signal processing unit SP is for each incoming line (input highway).
The call processing section cp finds the optimum route within the communication path for each call and sends a signal to that effect to the VCI conversion section 1-I.

The SSD is a self-routing switch device, and as shown in FIG. 3, the self-routing switch device 1SSD has a node N D * t = N D 33 consisting of 3×3 (9) self-routing switches.

Here, nodes ND, ... ~NDi3 and ND2□ ~ND2
3, there is a primary optical link Li□, L12.3. L□,
.

L21p Lz2HL231 L31p L32) L
33 and 5 nodes ND, □ to ND2. and ND, 1 to ND33 is a secondary optical link M□□HM
1□l M13T M2LIM222 M231 M3
12M)2 HM33.

Each node NDIj (1=1, 2p 3+ J=1+ 2
+3) has a switch section 2-I (I=1.2, 3; 4° 5.6; 7, 8.9), a buffer section 3-I, and a multiplexing switch section 4-I. However, below, this node N
In order to simplify the explanation of the configuration of Dij, the explanation will be given for the node ND. Of course, the configurations of other nodes also follow this.

That is, as shown in FIG. 4, the node NDo includes switch sections 2-1 to 2-3. It has buffer sections 3-1 to 3-3 and multiplexing switch sections 4-1 to 4-3.

Here, the switch section 2-I outputs input information to a desired output terminal based on the wavelength λX having the routing information TAG1 multiplexed by the vCI conversion section 1-■. is the wavelength group selection filter 2-
I-1, optical switches 2-11 to 2-I3. Drive circuit 2-
I-2, wavelength selection filter (wavelength selection switch) 2-I
-3.

Note that the switch units 2-I of the nodes constituting the same first-stage node group output the input information to a desired output terminal based on the wavelength λX having the routing information TAG1 multiplexed by the VCI converter 1-I. , the switch units 2-I of the nodes ND, □ to ND23 constituting the second stage node group are connected to V
Routing information TAG multiplexed by CI converter 1-■
Nodes ND, □~ which make up the third stage node group output the input information to a desired output terminal based on the wavelength λY having 2.
Switch section 2-'■ of ND33 is VCI conversion section 1-■
wavelength λ with routing information TAG3 multiplexed with
2, the input information is output to a desired output terminal.

22, the wavelength group selection filter 2-I-1 is for distributing only the wavelength λX. This is the other node ND that constitutes the first stage node group.

In the case of the wavelength group selection filter 2-I-1 of ND13, only the wavelength λX is distributed, but in the case of the wavelength group selection filter 2-I-1 of the nodes ND, -ND23 that constitute the second stage node group, Only the wavelength λV is distributed, and in the case of the wavelength group selection filter 2-I-1 of the nodes ND3° to ND33 forming the third stage node group, only the wavelength λ2 is distributed.

The optical switches 2-11 to 2-I3 transmit call information (wavelength λ.)
and routing information (wavelengths λY, λZ) to a desired output port. In the case of the optical switches 2-11 to 2-3 of the other nodes ND, . , λ2) to a desired output port, the optical switches 2-11 to 2 of the nodes ND, 1 to ND23 forming the second stage node group
- In the case of work 3, call information (wavelength λ.) and routing information (wavelength λZ) are switched to the desired output port, and the optical switch 2-■1 of nodes ND, 1 to ND33 that constitute the third stage node group ~2-I3, call information (wavelength λ.)
to the desired output port.

Note that the optical switches 2-11 to 2-work 3 are connected to the drive circuit 2-
When it receives the drive electrical signal from I-2, it turns on and directs optical information to the corresponding output port.

When it is off, it is configured so that no light is emitted from the output port.

The drive circuit 2-I-2 selects the optical switches 2-11 to 2 based on the detection result (optical signal) at the wavelength selection filter 2-I-3.
-I3 electrically, and has an optical/electrical converter and a driver for this purpose.

The wavelength selection filter 2-I-3 has wavelengths λ, to λ.

It detects either one of these and sends a message to that effect to the drive circuit 2-I-2. This is followed by other nodes ND1□, ND1. In the case of the wavelength selection filter 2-I-3, it also detects one of the wavelengths λ1 to λ and sends a message to that effect to the drive circuit 2-I-2, but the nodes constituting the second stage node group ND2□~ND2. In the case of the wavelength selection filter 2-I-3, the wavelength λ. ~λ,
detects one of them, sends a message to that effect to the drive circuit 2-I-2, and connects the nodes ND3□ to ND constituting the third stage node group.
3. In the case of the wavelength selection filter 2-I-3, the wavelength λ7
~λ, and sends a message to that effect to the drive circuit 2-I.
Send to -2.

Further, the buffer section 3-I avoids collision of information from each input terminal for each output terminal, and each buffer section 3-I
has a plurality (3) of buffers 3-11, . . . , 3-I3.

Furthermore, the multiplexing switch section 4-I multiplexes the optical signals from each buffer.

Next, a configuration example of the buffer section 3-I and the multiplexing switch section 4-I will be explained using FIG. 5.

First, each buffer is provided with a required number ND of delay lines DL made up of optical fiber loops corresponding to the time required to propagate one cell's worth of data, as represented by buffer 3-11, and an optical signal. It is configured with an optical switch O8W that switches whether or not to pass through the corresponding delay line DL, and an address identification information generator A.
It has an IG and a monitor section MT.

Here, the address identification information generator AIG generates input information (
(including routing information), this input information is output to the buffer side, and address identification information AI
is sent to the monitor section MT. Further, the address identification information AI has a wavelength of λS at the beginning and a wavelength of λR at the end, and its length is one cell.

The monitor unit MT includes a branch circuit PT that branches signals by the number ND of delay lines of the buffer, ND monitor lines MTL that receive signals branched by the branch circuit PT, and a monitor terminal MTT that has a detection unit DET. have.

All but one of the monitor lines MTL sends or transmits optical signals to a delay line DL, each consisting of an optical fiber loop corresponding to the time required to propagate one cell's worth of data, and to the next delay line DL. Optical switch OSW to switch between
and a bistable semiconductor laser BSLD provided at the connection part with the monitor terminal MTT, but when looking at each monitor, IiMTL, there is one pair of delay line DLM and optical switch 08WN. Those that are different are ND-
One exists.

The bistable semiconductor laser I3SLD has a flip-flop operation characteristic in that it is set (oscillates) when it receives the wavelength λS, and reset (stops oscillation) when it receives the wavelength λR, and this bistable semiconductor laser BSL
The output of D is input to the corresponding detection unit DET of the monitor terminal MTT.

With the above configuration, the wavelength λ. The cell that enters as an optical signal is converted to VCI by the VCI converter 1-I, and is also converted to a wavelength (TA) that determines the outgoing highway at each node.
G information) λX, λy, λZ are multiplexed. In this case, 1
In the node group in the third stage, the output port is determined by the wavelength λX, in the node group in the second stage, the output port is determined by the wavelength λV, and in the node group in the third stage, the output port is determined by the wavelength λ2.

Now, as an example, as shown in FIG. 7, the cell configuration of the input optical signal is data DATA and identification information vCI (a), and the identification information is converted to VCI (b), and routing information As, (λX, λV,
Considering the case where λ2) = (λ3.λ5.λ,) is multiplexed, in this case, at the first stage node ND, , the wavelength λ
Output port #3 is selected by , and inputted to the second stage node ND23, and in this second stage node NDo, output port #8 is selected by the wavelength λ, and inputted to the third stage node ND32. and then the third stage node ND3
2, output port #5 is selected by wavelength λ. As a result, input information is transferred from input terminal #1 to desired output terminal #1 by self-routing switching, as shown by the thick line in FIG.
It can be output to 5.

By the way, if a collision occurs between the information from each input terminal, the input information is temporarily stored in the buffer section 3-I, thereby avoiding the collision. That is, information first enters the address identification information generator AIG from the input port of the buffer section, but when input information comes in in this way, this address identification information generator AIG transfers this input information to the buffer side. At the same time, the address identification information AI is sent to the monitor section MT.

As shown in FIG. 5, the address identification information AI is branched into N0 pieces by a branch circuit PT. Then, the branched address identification information 1AI transmits the delay line DL set for each monitor line route, and connects the bistable semiconductor laser BS.
Arrive at LD. Each monitor line route is formed by cascading delay lines of optical fiber loops corresponding to the time required for one cell's worth of data to propagate, and the monitor line route leading to the bistable semiconductor laser BSLD is Since the delay amount of the semiconductor laser BSLD increases by one loop in order from the semiconductor laser BSLD drawn on the left in FIG. 5, the time for the address identification information AI to arrive at each bistable semiconductor laser BSLD is a time equivalent to one cell. They are off by one.

On the other hand, data information λ. , routing information (λY, λZp for the first stage node, λ for the second stage node
2. For the third stage node, there is no routing information.
Hereinafter, when referring to routing information, it is the same. ) is N0
is propagated on a transmission link formed by loop delay lines DT. Therefore, at the same time as a call comes in, the bistable semiconductor laser BSLD sequentially oscillates, and by detecting this point, information λ can be obtained. , it is possible to recognize the location on the fiber loop based on the routing information.

Therefore, when sending data to the output port, switch the optical switch ○ so that it goes straight from the current position without passing through the remaining loop.
In addition to controlling SW, the optical switch oswM of each route is also controlled so that the detected bistable semiconductor laser BSLD does not oscillate from the subsequent bistable semiconductor laser BSLD. The example in FIG. 5 shows a state in which the detection is performed by the second detection unit DET from the left, and the one indicated by the arrow among the optical switches ○sw and osw is turned on. In this state, the input information is transferred to the optical switch O8 indicated by the arrow in the buffer.
It passes through the delay line DT corresponding to the part W and is input to the multiplexing switch section 4-I, and the address identification information AI for monitoring does not proceed beyond the optical switch OSW shown by the arrow. , this resets the monitor function.

Note that information from other input ports also operates on the same principle,
Information from all input ports is output sequentially and evenly.

Thus, based on the wavelength with routing information,
Since information can be exchanged in the form of light using the ATM method, that is, asynchronously, it is fully compatible with higher speeds and larger volumes of information. Furthermore, the presence of the buffer section can reliably prevent information from each input terminal from colliding with each other.

By the way, in the above embodiment, 3×3 nodes NDi
Although the self-routing switch device SSD with j has been described, this self-routing switch device SSD
Generally, as shown in Figure 8, nodes with m incoming lines and m outgoing lines are used in the first and third node groups, and nodes with m incoming lines and m outgoing lines are used in the intermediate second level node group. It can be expanded to use nodes with n incoming lines and n outgoing lines.

FIG. 9 shows how the wavelengths λX, λV, and λ2 are allocated in this case. As can be seen from FIG. 9, the wavelengths λX, λY, and λ2 are assigned to be different wavelengths for wavelength multiplexing.
Each wavelength is arranged at equal intervals with respect to the number of wavelengths equal to the number of output ports in the node. In addition, in Figure 6, (1) to (
The numbers in m) or (1) to (n) are the output port numbers in each node, and the numbers 1 to m below them.

1 to n indicate wavelength values.

Next, we will briefly explain the optical devices required to implement this method.

First, the performance required for each optical device is the switch scale for an optical switch, and the number of selection/conversion channels for a wavelength selection filter/wavelength conversion element. A light switch is required.

Its scale increases in proportion to max (m, n).

Further, the number of channels of the wavelength selection filter/wavelength conversion element may be 2m+n channels.

Note that the wavelength group selection filter is as shown in FIG.
Basically, it can be configured with a single wavelength selection filter. Here, in this FIG. 10, apl is an optical branching device, and cp2 is an optical multiplexer.

λ3Wz to λSV3 are single wavelength selection filters.

Furthermore, the number of optical fiber loop delay lines in the buffer section 3-I, ie, the buffer length, is an important design parameter. The buffer length per outgoing line of one node is determined by link usage efficiency and discard rate. Now, if we set the data traffic drop rate to 10-9, the buffer length is
If the usage efficiency is 80%, it will be equivalent to 44 cells. Therefore, the number of fiber loops per person entering one outgoing line is approximately the value divided by the total number of incoming lines of one node.

Note that the VCI converter 1-I requires a variable wavelength selection filter or a variable wavelength conversion element. The number of channels is the same as in the case of switch section 2-I.

Furthermore, I would like to add a comment regarding traffic communication ability.

FIG. 11 shows the relationship between the number of highways and the number of wavelengths in this method. The switch size per node is determined by setting the limit to 16×16, and selecting the values of m and n that minimize the number of wavelengths. Therefore, in this method, the number of wavelengths is 4.
8 (the number of highways is 256), the node switch size is 16×16, so the graph shows that value as well.

Note that the difference in the number of wavelengths in this method increases as the sum of m and n.

Furthermore, based on the results shown in FIG. 11, FIG. 12 shows the relationship between the number of wavelengths and the number of accommodated channels when the speed per channel is 150 Mbps.

As for the highway speed, the current target (for the time being) is 1.6G optical fiber transmission system has already begun to be introduced in trunk systems and the high-speed modulation characteristics of the elements.
．． 6 Gbps is set to 10 Gbps in anticipation of the possibility of system operation of 10 Gbps or more by using optically controlled elements.

In addition, various wavelength control devices have been researched and experimented with due to differences in element structure, control method, etc., and the number of selectable and variable channels is limited by the wavelength interval and variable wavelength width. At present, we can expect about 10-odd wavelengths. Note that in the future, it will be possible to realize up to about 100 wavelengths.

Considering the above, the current situation (highway speed; 1.6
As shown in FIG. 12, the number of channels that can be accommodated in the communication path of Gbps (number of wavelength channels: 16) is approximately 340 channels.

However, in the future (highway speed: 10 Gbps, number of wavelength channels: 48), it will be possible to accommodate 17,000 channels.

In addition, the above-mentioned wavelength selection filter/wavelength conversion element selection/
The number of conversion channels is the value required when configuring a communication path with the same element, but with fixed selection filters and conversion elements, it is not necessary to satisfy the total number of channels, and it is necessary to selectively convert the wavelength to be selected and converted. It is good if you have the ability to do so. In addition, although the number of elements is increased in the variable selection filter/conversion element, by configuring the selection width/variable width by dividing it, the required performance is less strict than when configuring it with one. This allows the number of accommodated channels to be increased.

[Effects of the Invention] As detailed above, according to the optical ATM switching system of the present invention, input information can be exchanged optically in the ATM system, that is, asynchronously, based on the wavelength having the routing information multiplexed with the input information. Therefore, it can sufficiently cope with high-speed and large-capacity information, and the presence of the buffer section also has the advantage of reliably avoiding mutual collision of information from each input terminal.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention, and FIG. 2 is an overall block diagram showing an embodiment of the present invention. FIG. 3 is a block diagram of a self-routing switch device, FIG. 4 is a block diagram of a node, FIG. 5 is a block diagram of a buffer section and a multiplexing switch section, and FIG. 6 is a diagram explaining how to allocate wavelengths. FIG. 7 is a block diagram illustrating the state of self-routing. FIG. 8 is a block diagram of a self-routing switch device with an expanded number of nodes. FIG. 9 is a diagram explaining how to allocate wavelengths in the case of FIG. 8. Figure 10 is a block diagram showing an example of a wavelength group selection filter configured with a single wavelength selection filter, Figure 11 is a graph showing the relationship between the number of highways and the number of wavelengths, and Figure 12 is a graph showing the relationship between the number of wavelengths and the number of accommodated channels. A graph showing the relationship. FIG. 13 is a block diagram showing a conventional example. In the figure, 1-I is a VCI conversion unit (wavelength multiplexing unit), 2-I is a switch unit, 2-I-1 is a wavelength group selection filter, 2-I-11 to 2-I-33 are optical switches, and 2-I-1 is a wavelength group selection filter. -I-2
is a drive circuit, 2-I-3 is a wavelength selection filter, 3-I is a buffer section, and 3-IJ is a buffer. 4-I is a multiplexing switch section, AIG is an address identification information generator, and BSLD is a bistable semiconductor laser. cp is a call processing unit, apl is an optical demultiplexer, cp2 is an optical multiplexer, DET is a detection unit, DL, DL are delay lines, Lij, Mij are optical links, MT is a monitor unit, MTL is a monitor line, MTT is a monitor terminal. NDij is a node (self-routing switch), OS
w and osw are optical switches, PT is a branch circuit, SSD is a self-routing switch device, sp is a signal processing unit, and λS%11 to λsw3 are single wavelength selection filters. 〆↑1×3 2-1-1-11 wavelength #expletive filter apl --- Optical intermediary detector cp2 --- 1 combination island χswt ~ xsws --- 1 wavelength sad selection filter pump eldest son Selected fill and 1″S length) 1 stone fill θ°
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figure

Claims (1)

[Claims] A wavelength multiplexing unit (1-I) that multiplexes a wavelength having routing information within a communication path onto an input optical signal of a required wavelength having input information; and the wavelength multiplexing unit (1-I). a switch unit (2-I) for outputting the input information to a desired output terminal based on the wavelength having the routing information multiplexed with the buffer; and a buffer for avoiding collision of information from each input terminal for each output terminal. The wavelength multiplexing section (1-I) multiplexes wavelengths having the routing information, and performs switching by self-routing based on the wavelengths, thereby converting the input information into the desired information. An optical ATM switching system characterized by output to an output terminal.