KR0150525B1 - Output recontending space/code mixed type optical switching system - Google Patents

Abstract

The present invention provides a space / code mixed optical switching method for obtaining a yield of several Tb / s or more in a large-capacity ATM switch capable of accommodating not only voice and data still images but also large-capacity subscriber video services such as HDTV distribution services. An output re-compete space / code mixed optical switching system comprising: a space split optical switch having N + Nf input / output terminals; A one-cell retarder connected to the output terminal and the input terminal of the spatial division optical switch by Nf optical fiber lines, respectively; N variable code converters connected to N input optical fiber lines to an input terminal of the spatial division optical switch; An L × N code inverse converter of L units connected to N output optical fiber lines to an output terminal of the spatial division optical switch; And a switch controller interconnected to the space division optical switch and the N variable code converters by unidirectional control signal lines and electrical transmission / reception control buses, respectively.

Description

Output Rematch Space / Code Mixed Optical Switching System

1 is a block diagram of an ATM optical switching system.

2 is a schematic diagram of a two-cell timeslot output re-contrast optical switching module.

3 is an exemplary configuration diagram of (N + Nf) × (N + Nf) spatial division optical switches and one cell retarder.

* Explanation of symbols for main parts of the drawings

1: space division optical switch 2: switch controller

3: 1 cell delay 4: variable code changer

5: code inverse converter

The present invention provides a space / code mixed optical switching method for obtaining a yield of several Tb / s or more in a large-capacity ATM switch capable of accommodating not only voice and data still images but also large-capacity subscriber video services such as HDTV distribution services. An output rematch space / code mixed optical switching system according to the present invention.

In general, optical exchange technology, unlike conventional electronic exchange technology, has incoherence between signals, low signal loss on optical fiber, high speed of switching, wide power to burnout and low signal loss in parallel processing, high speed of switching, and transmission. It has the inherent advantage of taking advantage of the broad bandwidth and parallel processing capability. In addition, since a switch node in a broadband network provides ATM switching service for hundreds of Mb / s transmission links, an ATM switch having a Tb / s level yield is required at the cell level.

Considering the requirements of the switch node and the limitations of the optical device technology for cell processing and buffer implementation at the ATM level, the call control function and the ATM cell processing function have electronic technology and Tb / s-class switching. Each of the required magnetic routing switches has optical switching technology.

In implementing the N × N self-routing optical switch, in the conventional wavelength division type spatial switch, an output contention algorithm that spans two cell-timeslots can achieve an optical element reduction effect of about 50% at a single output stage. When implementing the optical switch (that is, if N is large), the dimension of the star coupler becomes very large (N + N / 2) (4N + N / 2), and about N2 single frequency laser diodes and frequency variable filter There was a disadvantage to be added. In the case of the spatial / wavelength mixed optical switch, since multiple cells are multiplexed to different wavelengths in the internal link on the spatial switch, the size of the spatial switch is maintained at N × N, which is suitable for implementing a large capacity switch. Since output contention is performed only for the timeslot time, the number of wavelength-variable light sources is too large to guarantee a certain level of cell loss.

The present invention devised to solve the problems of the prior art maintains a constant cell loss rate by applying an output contention algorithm that spans two cell-time slots as in a wavelength division space switch to a basic space / code mixed optical switch structure. It is an object of the present invention to provide an output re-contending space / code mixed optical switching system which minimizes the number of code inverse converters required for the output stage and the size of the space division optical switch.

In order to achieve the above object, the present invention provides a self-routing optical switching system of a large-capacity ATM optical switching system, comprising: a space division optical switch having N + Nf input / output terminals; A one-cell retarder connected to the output terminal and the input terminal of the spatial division optical switch by Nf optical fiber lines, respectively; N variable code converters connected to N input optical fiber lines to an input terminal of the spatial division optical switch; An L × N code inverse converter of L units connected to N output optical fiber lines to an output terminal of the spatial division optical switch; And a switch controller interconnected to the space division optical switch and the N variable code converters by unidirectional control signal lines and electrical transmission / reception control buses, respectively.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

1 is a schematic configuration diagram of an ATM optical switching system in which an electronic technology and an optical switching technology are applied to the present invention, wherein the input / output signals are an ATM cell having a speed of v (e.g., 155 Mb / s). Each cell is 53 bytes long.

The cell multiplexer 20 implemented as an electronic circuit is connected to the optical switching module 10 by a data bus of a speed V (eg, 2.5 Gb / s), and the input cells are processed by the header converter 30 in the header processing unit. And then stored in an input buffer memory within cell multiplex 20 to avoid cell loss caused by instantaneous call congestion.

The optical switching module 10 receives a plurality of cells on the same cell-timeslot from the multiple cell multiplexes 20 and then to the cell demultiplexer 40 via a data bus whose output switching capacity is LV. It performs a self-routing switching function that can output up to L input cells. That is, when the N input cells in the optical switching module 10 are to be switched to the same destination cell demultiplexer 40, the N-L cells are lost, thereby reducing the overall yield of the optical switching system.

The cell demultiplexer 40 implemented as an electronic circuit processes the cells input from the optical switching module 10 in the header converter 50, and stores them in a buffer for a while to avoid cell loss. Output at a speed of v (e.g., 155 Mb / s). Therefore, the switching capacity of the ATM optical switching system depends on the structure of the optical switching module 10 and the self-routing switching scheme, and the variable code is applied by applying an output contention algorithm over two cell-time slots to the spatial / code mixed optical switch structure. A schematic configuration diagram of the optical switching module 10, which can minimize the number of converters and code inverse transformers and the size of the spatially divided optical switch, is shown in FIG.

2 is a structural diagram of an optical switching module 10 capable of minimizing a switch size and the number of variable code converters and code inverse converters while maintaining a low cell loss rate. And a one-cell delay (3), N variable code converters (4), and code inverse converters (5).

The input / output terminals of the spatial division optical switch 1 are connected to the N variable code converters 4, the code inverse converter 4 and the code inverse converter 5 in one direction by N input / output optical fiber lines, respectively, 2) is connected to the space division optical switch 1 and the unidirectional switch control signal line, and is interconnected with the N variable code converters 4 by N electrical transmission and reception control buses in both directions.

The one-cell retarder 3 is interconnected with Nf optical fibers, respectively, with the input / output terminals of the spatial division optical switch 1.

As shown in the figure, referring to the switching operation for a plurality of input cells, after each cell arrives at the variable translator 4, routing information for each cell is transmitted by each variable translator 4; It is sent to the switch controller 2 via the control bus, and the arbiter in the switch controller 2 receives each cell in each variable code converter 4 according to routing information of the cell received from each variable code converter 4. The code information to be converted is responded to the variable code converter 4 via the reception control bus, and the switch controller 2 also controls the path between the input terminal and the output terminal of the spatial division optical switch 1. Each variable code converter 4 converts an input cell into one of codes 1 to L according to the code information received from the switch controller 2, and the converted cells are internal to the space division optical switch 1 It is switched to the destination output with code multiplexing along the path. If more than L input cells are to be switched to the same output stage of the spatial division optical switch 1, cells that have failed contention by the arbiter in the switch controller 2 are output once more at the next cell-timeslot time. In order to compete, the code 1 is converted to one of the codes L, and the code is multiplexed at the output terminal of the spatial division optical switch 1 and switched to the one-cell delay unit 3. Cells that are code-multiplexed and pass through the one-cell delay unit 3 are output contended in preference to cells newly input to the variable code converter 4, and are controlled by the switch controller 2 to perform the spatial division optical switch 1 Is switched to the output stage. By default, contention is performed over two cell-timeslots, but still discards failed cells. Each code inverse converter 5 receives up to L cells multiplexed from the output terminal of the spatial division optical switch 1 with L fixed code inverse converters and outputs them to the cell demultiplexer.

Therefore, as in the present invention, a space division optical switch 1, a switch controller 2, a one-cell delay unit 3, N variable code converters 4, and N × L code inverse converters 5 are composed of The optical switching module performs output contention over two cell-timeslots, thereby maintaining the required cell loss rate while reducing the value of L, thereby reducing the number of codes required for output contention. . In addition, since cells that have failed in contention in the first cell-timeslot are also code-multiplexed and stored in the one-cell delay unit 3, the number of input / output terminals Nf added to the spatial division optical switch 1 is also reduced to N / 6. It is advantageous for the implementation of this large switching module.

FIG. 3 shows a space division optical switch 1 having a size of (N + Nf) × (N + Nf) in the inventive device capable of minimizing the number L of codes and the size of the space division optical switch. An example of the implementation of the one-cell delay unit 3 is shown.

As shown in FIG. 3, the space division optical switch 1 of (N + Nf) × (N + Nf) is composed of N + Nf optical space switches 6,7 and N + Nf optical couplers 8,9. The one cell delay unit 3 is composed of Nf optical fiber delay lines 10. The optical space switches 6, 7 connected to the switch controller 2 by unidirectional control signal lines have one input terminal and one output terminal. The N optical space switches 6 connected to the variable code converter 4 by an input optical fiber line are interconnected one-to-one to each of the N + Nf optical couplers 8 and 9 by means of unidirectional optical transmission buses. However, the output ends of the Nf optical space switches 7 connected to the output ends of the optical fiber delay lines 10 are configured to be connected one-to-one to only N optical couplers 8 by a unidirectional optical transmission bus. Therefore, in the case of the optical coupler 9 and the optical space switch 7 which are connected one-to-one to the input terminal and the output terminal of the optical fiber delay line 10, Nf pieces of the N + Nf input / output terminals are not connected. The N optical couplers 8 are connected to the code inverse converter 5 one-to-one with one output optical fiber line. Now, as an example, when L + 2 input cells are switched to the same output stage of the spatial division optical switch 1, by the arbiter in the switch controller 2, the L cells which have successfully competed are converted into the variable translator 4 In the code 1, code 2, ... code L, the remaining two cells that have failed to compete are converted into the code 1 and code 2 by the variable code converter 4 and input to the optical space switch 6, respectively. The L cells which have successfully competed are output to the unidirectional optical transmit bus connected to the incoming optical coupler 8 at the input of each optical space switch 6 under the control of the switch controller 2, and the incoming optical coupler 8 Code-multiplexes cells input with L different codes and outputs the codes to the code inverse converter 5 through the output optical fiber line.

The two cells which failed to compete in the first cell-timeslot are output to one optical coupler 9 designated at the input of each optical space switch 6 under the control of the switch controller 2, and the designated optical coupler 9 The two input cells are code multiplexed and output to the input terminal of the optical fiber delay line 10. After the two codes multiplexed are delayed by one cell-timeslot in the optical fiber delay line 10, the unidirectional light is connected to the incoming optical coupler 8 at the input of the optical space switch 7 under the control of the switch controller 2. Output to the send bus. The incoming optical coupler 8 receives the two cells that failed to compete in the first cell-timeslot and the input cells that successfully converted in the second cell-timeslot to one of code3, code4, ... codeL. After multiplexing the code up to L, it outputs to the code inverse converter 5 through the output optical fiber line.

As described above, according to the apparatus of the present invention, there are 1 x (N + Nf) optical space switches (6, 7) N + Nf and (N + Nf) × 1 optical coupler (8, 9) N + Nf In the single cell retarder 3 configured by using the (N + Nf) × (N + Nf) space division optical switch 1 and the Nf optical fiber delay lines 10, the space division optical switch 1 N variable code converters (4) and the output side of the one-cell delay (3) is connected to the input terminal of the optical fiber cable, and the N code inverse converter (5) consisting of L at the output terminal of the spatial division optical switch (1) and The input side of the one-cell retarder 3 is connected to the optical fiber, and the switch controller 2 is a unidirectional control signal line of the spatial division optical switch 1 and is interconnected with the N variable code converters 4 by a bidirectional transmission and reception control bus. Then, the contention in the switch controller 2 causes the input cells to perform output contention over two cell-timeslots, thereby allowing the contention to succeed in the first cell-timeslot. After converting to the designated code, the code multiplexes and switches directly to the output terminal of the spatial division optical switch 1, and in the case of a cell that has failed contention, the second cell after passing through the one cell delay unit 3 in the code multiple state- By switching in the timeslot, it is possible to maintain a constant cell loss rate while reducing the number of code inverse converters 5, i.e., L required for one output stage, and the number of variable code converters and the size of the space division optical switch 1 It can also be reduced, which is suitable for the implementation of a large capacity optical switching module.

(Reference: As a result of analyzing the performance of the optical switch of the present invention, under the load condition of ⓐ Pqⓐp = 0.9 and the cell loss condition of 10-ⓐH-6ⓐh, the output switching capacity L = 4 is required, It was confirmed that the size of the switch is (N + N / 6) × (N + N / 6).)

Claims (3)

A magnetic routing optical switching system of a large capacity ATM optical switching system, comprising: a space division optical switch (1) having N + Nf input / output terminals; A one-cell retarder 3 connected to the output terminal and the input terminal of the spatial division optical switch 1 by Nf optical fibers, respectively; N variable code converters 4 connected to the input terminals of the space division optical switch 1 by N input optical fiber lines; An L × N code inverse converter 5 of L units connected to N output optical fiber lines to an output terminal of the spatial division optical switch 1; And a switch controller (2) interconnected to the space division optical switch (1) and the N variable code converters by unidirectional control signal lines and electrical transmission / reception control buses, respectively. 2. The number of input / output terminals (Nf) added to the space division optical switch (1) for output re-competition according to claim 1, via the one-cell delay (3) in a code-multiplexed state for a cell that has failed contention. By outputting to the code inverse converter 5 in the second cell time slot, the number of additional input / output terminals of the space division optical switch 1 for satisfying a predetermined level of cell loss condition is N / 6. Switch (1) has an output repetition space / code mixed optical switching system, characterized in that the number of input and output terminals of N + N / 6. The N-type optical space switch 6 according to claim 1, wherein the spatial division optical switch 1 is connected to the N variable code converters 4 and the switch controller 2 by an input optical fiber line and a control signal line, respectively. ; Nf second optical space switches (7) connected to the output terminal and the switch controller (2) of the one-cell retarder (3), respectively, by an input optical fiber line and a control signal line; N first optical couplers 8 connected to N + Nf optical space switches and output stages and L × N code inverse converters 5 by N + Nf unidirectional optical transmission buses and output optical fiber lines, respectively; And Nf second optical couplers 9 connected to the N first optical space switch output stages and the input terminals of the one cell retarder 3 by N unidirectional optical transmission buses and output optical fiber lines, respectively. Output re-compete space / code mixed optical switching system.