KR19980026749A - Photonic Switching System with Combined SD and WD - Google Patents

Abstract

The present invention relates to a wavelength group multiple distributed spatial / wavelength mixed optical switching method in a large-capacity ATM switch, wherein a self-routing optical switching system is configured in parallel with m optical switching subsystems having n input / output terminals, and each optical The switching subsystem includes a space division optical switch module having n + nf input / output terminals; one cell delay means connected to an output terminal and an input terminal of the space division optical switch module by nf optical fiber lines; N input modules connected to input terminals of the space division optical switch module by n input optical fiber lines; A common buffer controller connected to the n input modules by bidirectional control signal lines, respectively; Unidirectional control signal line means for interconnecting the n input modules in a ring form; N wavelength group demultiplexers connected to an output terminal of the spatial division optical switch by n output optical fiber lines; And n output modules connected to each of the optical switching subsystems by the wavelength group demultiplexer and the m output fiber lines in the m optical switching subsystems.

Description

Photonic Switching System with Combined SD and WD

1 is a block diagram of an ATM optical switching system to which the present invention is applied.

2 is a block diagram of a wavelength group multiple distributed optical switching system according to the present invention.

3 is a block diagram of a space division optical switch module according to the present invention.

4 is a block diagram of an input module according to the present invention.

5 is a view for explaining a wavelength variable range of a laser diode.

6 is a block diagram of an output module according to the present invention.

Explanation of symbols on the main parts of the drawings

1: Space division optical switch module 2: 1 cell retarder

3: input module 4: wavelength group demultiplexer

5: output module 6: common buffer controller

The present invention relates to a spatial / wavelength mixed optical switching system, particularly in a large-capacity ATM switch capable of accommodating not only voice / data and still images but also large-capacity subscriber video services such as HDVT distribution services. A wavelength group multiple distributed spatial / wavelength mixed optical switching system for yield.

In general, in implementing a NxN self-routing optical switch, in the conventional wavelength division type spatial switch, the reduction of the number of optical elements of about 50% can be achieved by applying the contention resolution process over two time slots. When implementing a large capacity optical switch (that is, when N is large), the dimension of the star coupler becomes very large (N + N / 2) × (4N + N / 2), and about N / 2 single frequency laser diodes There was a disadvantage that a variable frequency filter had to be added.

In addition, even in the existing spatial / wavelength hybrid optical switch in which multiple cells are switched to different wavelengths in the internal link on the spatial switch to perform switching, a fixed filter required at the output stage by applying contention resolution over two time slots of a distributed structure. Although the number and the size of the space division optical switch can be minimized, the control of the space division optical switch and the expansion of the exchange capacity are easy, but the input / output dimension N of the switch increases due to the structure of the single optical switching system. In addition, since the order of the space split optical switch is also increased, there are many problems in realizing the high degree optical switching system.

In order to solve the above problems of the prior art, the present invention is to construct a spatial / phage hybrid optical switching subsystem using a ring-type contention retention resolution of a basic dispersion structure in parallel and to each subsystem By applying different wavelength groups, it is easy to control the spatial division optical switch and contention fesolution over two time slots while minimizing the size of the spatial division optical switch under constant cell loss conditions, and simple expansion of the optical switching subsystem unit. The purpose of the present invention is to provide a spatial / wavelength mixed optical switching system of a distributed structure that can easily expand the total capacity of the optical switching system.

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, wherein the magnetic routing optical switching system is configured in parallel with m optical switching subsystems having n input / output terminals, Each optical switching subsystem includes a space division optical switch module having n + nf input / output terminals; One cell delay means connected to the output terminal and the input terminal of the space division optical switch module by nf optical fiber lines; N input modules connected to input terminals of the space division optical switch module by n input optical fiber lines; A common buffer controller connected to the n input modules by bidirectional control signal lines, respectively; Unidirectional control signal line means for interconnecting the n input modules in a ring form; N wavelength group demultiplexers connected to an output terminal of the spatial division optical switch by n output optical fiber lines; And n output modules connected to each of the optical switching subsystems by the wavelength group demultiplexer and the m output fiber lines in the m optical switching subsystems.

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

1 is a block diagram of a large-capacity ATM optical switching system in which an electronic technique and an optical switching technique to which the present invention is applied are mixed.

As shown in FIG. 1, in an ATM optical exchange system in which electronic and optical technologies are mixed, input / output signals are ATM cells having a speed of v (e.g., 155 Mb / s), each of which has a length of 53 bytes. Have

The cell multiplexer 200 implemented as an electronic circuit is connected to the optical switching system 100 by a data bus of a speed V (eg, 2.5 Gb / s), and the input cells are processed by the header converter 300 in the header processing unit. And then stored in an input buffer memory within the cell multiplexer 200 to avoid cell loss caused by instantaneous call congestion.

The optical switching system 100 receives a plurality of cells on the same time slot from the multiple cell multiplex 200, and then scans the destination address of each cell to have the destination address through a data bus having a speed of V. The cell demultiplexer 400 performs a self-routing switching function for outputting input cells.

And even if multiple input cells are simultaneously switched to the same incoming cell demultiplexer 400 with a spatula, the optical switching system 100 must maintain a minimum cell loss rate so that the overall yield of the optical exchange system is not reduced. .

The cell demultiplexer 400, which is implemented as an electronic circuit, processes the cells input from the optical switching system 100 in the header converter 300, and then temporarily stores the cells in a buffer to avoid cell loss and stores ATM cells v ( Example Output the speed of 155 Mb / s).

Therefore, it depends on the structure and switching method of the switching capacitive optical switching system 100 of the ATM optical switching system, and it is possible to easily increase the capacity by constructing the basic unit space / wavelength mixed optical switch in parallel, and 2 times By applying the contention reclamation process over the lot, the number of fixed filters required for the output stage and the size of the spatial division optical switch can be minimized.

2 is a schematic configuration diagram of an optical switching system 100 according to the present invention, which can minimize the switch size and the number of wavelength filters while maintaining a low cell loss rate, and increase the capacity of the optical switching subsystem 500. Because it is made easy.

The optical switching system 100 as shown in FIG. 2 is configured to have a parallel structure with m optical switching subsystems 500, and each subsystem 500 includes a spatial division optical switch module 1, It consists of a one cell retarder (2), n input modules (3), n wavelength group demultiplexers (4), n output modules (5), and a common buffer controller (6).

The input / output terminals of the spatial division optical switch module 1 are connected to the n input modules 3 and the wavelength group demultiplexer 4 in one direction by n input / output optical fiber lines, respectively, and the one cell delay unit 2 is a space. The input and output terminals of the split optical switch module 1 are connected to each other by nf optical fibers.

The input terminal of the output module 5 is interconnected by the m optical fiber lines with the output terminal of the wavelength group demultiplexer 4 in the m optical switching subsystem 500.

The common buffer controller 6 is connected to the n input modules 3 with bidirectional control signal lines, respectively, and the n input modules 3 are connected to each other in a ring form with the unidirectional control signal lines 7.

Now, referring to the above configuration, referring to the switching operation of the plurality of cells inputted, after each cell arrives at the input module 3, each input module 3 interprets the destination address of the cell and is unidirectional. The contention recreation using the control signal line 7 is performed to convert the wavelength of each input cell so that wavelengths do not overlap with respect to each output terminal of the spatial division optical switch module 1.

The unidirectional control signal line 7 is composed of m parallel buses corresponding to the optical switching subsystem 500, and n contention leisure packets (CR packets) corresponding one to one to the destination address are input to each parallel bus. Cycles from the input module 3 to the input module 3 n once in the time slot 1 time of the cell.

Each contention recreation packet (hereinafter, referred to as a CR packet) stores up to L switching state information of the input cell and the current one cell timeslot time for one destination address.

Each input module 3 interprets the destination address of the input cell and, when a CR packet having the destination address is received from the previous input module 3, converts the wavelength information to be used for wavelength conversion from the state information of the CR packet by one time. It is determined not to overlap in the order of the slot previous state information and the current state information, and after changing the state of the CR packet, the CR packet is transmitted to the next input module 3.

After completion of the contention recreation process for one cycle, each input module 3 replaces the current state information of the CR packet with the state information before the one cell timeslot time, and performs the same process for the cell input next time. Repeat.

Therefore, the state information before one cell timeslot of each CR packet has information on the number and wavelength of cells switched from the previous timeslot to the corresponding destination output stage based on the current cell input time.

Since up to L switching state information before one time slot can be stored, wavelength conversion is performed by designating different wavelengths for up to L input cells.

In addition, since the current switching state information may have up to L, in general, if the value of the previous switching state information is I at any instant, different wavelengths may be applied for up to 2L-I input cells through contention recreation process. It is selected and switched to the terminating output stage, and further input cells are not selected for wavelength so that loss processing is performed.

When the destination address of the input cell is translated and switched to another optical switching subsystem 500, the contention recreation is carried out as described above through one of the m parallel buses 7 corresponding to the optical switching subsystem 500 one-to-one. The process is carried out and only by selecting different wavelength groups to avoid wavelength duplication.

That is, the wavelength conversion for the input cell is the wavelength group λ11, λ12, ... λ1L when the destination address of the cell is the output terminal for the optical switching subsystem 500, wavelength group if the optical switching subsystem 500 In the case of lambda 21, lambda 22, ... lambda 2L, and optical switching subsystem 500 m, they are selected in the wavelength groups lambda m1, lambda m2, ... lambda mL, respectively.

When multiple cells entering the input of the optical switching subsystem 500 are switched to the output of any optical switching subsystem 500, if the number of input cells continues to be less than L, the corresponding m parallel buses 7 Through the contention recreation process, one can convert up to L different wavelengths from previous timeslot state information in the corresponding wavelength group, so that it is switched to the incoming output stage without any time delay in the wavelength multiplexed state. .

However, in general, when the state information before 1 timeslot time of the CR packet is I and I cells are already waiting in the 1 cell delay unit 2, the LI input cells from the previous switching state information of the contention recreation process Is switched to the incoming output stage without any time delay, and the other input cells perform wavelength conversion differently from the current switching state information of the contention recreation process up to L, and these cells are one-cell retarder (2). Space division optical switch module receiving routing information including address of 1 cell delay unit 2 from common buffer controller 6 and inserting it into cell header so that it can be stored for 1 timeslot and then switched to the corresponding output stage. Send to

When the common buffer controller 6 receives the use request signal (including the destination address) of the one-cell delayer 2 from the input module 3, the common buffer controller 6 classifies the destination address, and the destination optical switching subsystem 500 number is different but the subsystem. Routing information including the address of the one cell delay unit 2 is sent to the corresponding input module 3 so that the same destination address in 500 may be stored in the wavelength multiplexed for one timeslot time.

The wavelength multiple space division optical switch module 1 interprets the routing information of the input cell received by the input module 3, and if the routing information does not include the one-cell delayer 2 address, the wavelength corresponding to the called address. Switch to the output of the multi-segment optical switch module 1, and switch to the output of the spatial-division optical switch module 1 to which the corresponding one-cell retarder 2 is connected if the one-cell retarder 2 address is included. .

The input cell received from the one cell delay unit 2 is switched to the output terminal of the spatial division optical switch module 1 corresponding to the destination address in the routing information.

As a result of the contention recreation process over two timeslots, which overlap the current and previous switching state information of the CR packet, the input cells have two switching opportunities, thereby maintaining the required cell loss rate while reducing the value of L. As a result, the number of wavelengths used for wavelength conversion can be reduced, thereby reducing the number of filters.

In addition, since the input cells converted from the current state information of the CR packet are also wavelength-multiplexed and stored in the one-cell retarder 2, the number of input / output terminals nf added to the spatial division optical switch module 1 is also reduced and large capacity. It is advantageous to the implementation of the optical switching module.

The wavelength group demultiplexer 4 receives mL input cells multiplexed in m wavelength groups from the output of the spatial division optical switch module 1 to the same destination output in the m optical switching subsystem 500, and these Demultiplexes the wavelength signal by wavelength group.

The wavelength group demultiplexer 4 is the demultiplexed wavelength group signals [lambda] 11, [lambda] 12, ... [lambda] 1L are output modules 5 of 1 of the optical switching subsystem 500, and the wavelength group signals [lambda] 21, [lambda] 22, ... [lambda] 2L is the output module 5 of the optical switching subsystem 500, and the wavelength group signals [lambda] m1, [lambda] m2, ... [lambda] mL are the output modules 5 of the optical switching subsystem 500m, respectively. Send.

Each output module 5 receives up to mL cells through m fiber optic lines from the output of m wavelength group demultiplexers 4 in different optical switching subsystems 500.

The wavelength group signal of the cells input from the wavelength group demultiplexer 4 to the output module 5 corresponds to the optical switching subsystem 500 to which the output module 5 belongs, so that within one optical switching subsystem 500. All output modules 5 receive signals of the same wavelength group through m optical fiber lines.

When the output module 5 is in the optical switching subsystem 500 i, each output module 5 must receive mL cells each wavelength multiplexed in wavelength group i, so L for each wavelength group i Receive up to mL cells using m fixed filters (wavelength filter i1, wavelength filter i2, ... wavelength filter iL) with L selectable cells.

Since each output module 5 is connected to the cell demultiplexer 400 with a data bus having a speed of V, the output modules 5 are temporarily stored in a buffer to prevent cell loss, and then the cells are sequentially transferred to the cell demultiplexer 400 in order. Output

Therefore, as in the present invention, the optical switching system 100 is configured to have a parallel structure with m optical switching subsystems 500, and each subsystem 500 includes a space division optical switch module 1 and a one cell retarder. (2) Consisting of contention recreation process over 2 time slots, consisting of n input modules (3), n wavelength group demultiplexers (4), n output modules (5), and common buffer controllers (6) Since the input cells have two switching opportunities, the required cell loss rate can be maintained while reducing the value of L, thus reducing the number of wavelengths used for wavelength conversion, thereby reducing the number of filters.

Since the input cells, which are wavelength-converted from the current state information of the CR packet, are also wavelength-multiplexed and stored in the one-cell delay unit 2, the number of input / output terminals nf added to the spatial division optical switch module 1 is also n / ( L + 1) is sufficient, which is advantageous for implementing a large capacity optical switching module.

3 shows the size of (n + nf) × (n + nf) in the device of the present invention, which can minimize the number L of wavelengths required for wavelength conversion and the size of the space division optical switch module 1 as described above. FIG. 1 is a configuration diagram of a space division optical switch module 1 and a one cell retarder 2. FIG.

As shown in FIG. 3, the space division optical switch module 1 of (n + nf) × (n + nf) is composed of n + nf optical space switches 10,11 and n + nf optical couplers 12,13. The one cell retarder 3 is composed of nf optical fiber delay lines 14.

The optical space switches 10 and 11 have one input terminal and n + nf output terminals, and the optical coupler 12 and 13 have n + nf input terminals and one output terminal. The n optical space switches 10 connected to the input module 3 by the input optical fiber lines are connected one-to-one to the n + nf optical couplers 12 and 13, respectively, with their output terminals being unidirectional optical transmission buses. The output ends of the nf optical space switches 11 connected to the output ends of the optical fiber delay lines 14 are configured to be interconnected one-to-one only to the n optical couplers 12 by a unidirectional optical transmission bus.

Therefore, in the case of the coupler 13 and the optical space switch 11, which are connected one-to-one to the input terminal and the output terminal of the optical fiber delay line 14, nf of n + nf input / output terminals are not connected.

The n optical couplers 12 are connected one-to-one to the wavelength group demultiplexer 4 by one output optical fiber line, respectively.

The optical space switch 10 interprets the routing information of the input cell received by the input module 3, and if the address of the one cell retarder 2 is not included, the optical space switch 10 is input to the input coupler 12 corresponding to the called address. If the one-cell delay device 2 address is included, the optical fiber delay line 14 is switched to the input terminal of the optical coupler 13 connected thereto.

The optical space switch 11 connected to the optical fiber delay line 14 switches to the input terminal of the optical coupler 12 corresponding to the destination address in the routing information of the input cell.

Therefore, in the optical fiber delay line 14, up to λ mL of input cells are divided into wavelength groups λ11, λ12, ... λ1L, wavelength groups λ21, λ22, ... λ2L, wavelength groups λm1, λm2, ... λmL, etc. 1 time slot time is stored as it is, and it is switched to the corresponding output stage at the next cell timeslot time.

Similarly, the optical coupler 12 also wavelength-multiplexes up to mL input cells with different wavelengths and outputs them to the wavelength group demultiplexer 4 through the output optical fiber line.

4 is a configuration diagram of the input module 3 performing the contention recreation process and the wavelength conversion function over two timeslots as described above.

As shown in FIG. 4, the input module 3 includes a cell buffer 30, a routing information inserter 31, a wavelength variable laser diode 32, a contention leisure solution, and a wavelength controller 33.

After one cell arrives from the cell multiplier 200 in the cell buffer 30, the destination address of the cell is transferred to the contention leisure solution and the wavelength controller 33, and the input cell is sent to the routing information inserter 31. Is sent.

The contention leisure solution and the wavelength controller 33 perform contention leisure process over two time slots using CR packets as described above through m contention leisure parallel buses (CR buses) that are unidirectional control signal lines 7. Do this.

That is, when the state information before 1 timeslot time of the CR packet received through the CR bus is less than L, one wavelength variable information is selected from the corresponding wavelength group by using the previous state information. After examining the current switching state information of the packet, it selects one wavelength variable information from the current state information only when it is less than L.

If the previous and current state information of the CR packet is larger than L, the wavelength cannot be designated for the input cell, so that the loss processing is performed.

After selecting one wavelength in this manner, the contention leisure solution and the wavelength controller 33 increase the corresponding state information by the wavelength selection process by 1 and send the CR packet to the next input module 3 through the CR bus. send.

When one wavelength is selected from the state information before one time slot time, since the use of the one-cell retarder 2 is not necessary, only the wavelength variable information is transmitted to the wavelength variable laser diode 32, and When the wavelength is selected from the switching state information, it is necessary to store one cell time in the one cell delay unit 2, so that the address of the one cell delay unit 2 is allocated from the common buffer controller 6 to the routing information inserter ( 31) and the wavelength variable laser diode 32 sends routing information and wavelength variable information, respectively.

The routing information inserter 31 inserts routing information into the header of the cell received from the cell buffer 30, and the wavelength variable laser diode 32 receives the cell received by the routing information inserter 31 according to the wavelength variable information. Is converted into wavelength and transmitted to the spatial division optical switch module (1).

5 shows m wavelength groups one-to-one corresponding to m optical switching subsystems 500 in order to avoid wavelength duplication in the input module 3 performing the wavelength conversion function. Is assigned one of the mL wavelengths shown from the contention recreation and wavelength controller 33.

6 is a schematic diagram of an output module 5 for receiving up to mL cells input from the output of the m wavelength group demultiplexer 4 in each optical switching subsystem 500.

As shown in FIG. 6, the output module 5 includes a fixed filter 50, a photoelectric converter 51, and a buffer memory 52.

The m fixed filters 50 are each connected via an optical fiber line connected to the m wavelength group demultiplexers 4 in the optical switching subsystem 5000 using fixed filters i1, i2, ... iL for wavelength group i, respectively. The input wavelength multiplexed cells are filtered into L wavelengths.

The photoelectric converter 51 photoelectrically converts input cells wavelength-filtered from the fixed filter 50 to L optical fiber lines using L photoelectric conversion circuits, respectively.

The output module 5 simultaneously receives and processes up to mL cells and stores them temporarily in the buffer memory 52 in order to prevent temporary cell loss. Output to the central portion (400).

As described above, according to the apparatus of the present invention, in the optical switching system 100 configured to have a parallel structure with m optical switching subsystems 500, each subsystem 500 is a space division optical switch module ( 1), consisting of one cell retarder (2), n input modules (3), n wavelength group demultiplexers (4), n output modules (5), common buffer controller (6), The input / output terminals of the switch module 1 are unidirectionally connected to the n input modules 3 and the wavelength group demultiplexer 4 with n input / output optical fiber wires, respectively, and the one cell delay unit 2 is a spatial division optical switch module. The input and output terminals of (1) are interconnected with nf optical fibers, respectively, and the input terminal of the output module (5) has an output terminal and m optical fiber lines of the wavelength group demultiplexer (4) in the m optical switching subsystem 500. Unidirectionally connected in the form of a ring between n input modules (3) By using the control signal line 7 and the common buffer controller 6 connected to the n input modules 3 as bidirectional control signal lines, the input leisure circuit has two switching opportunities. Since it is possible to maintain the required cell loss rate while reducing the value of L, the number of wavelengths used for wavelength conversion and the number of filters can be reduced.

Since the input cells, which are wavelength-converted from the current state information of the CR packet, are also wavelength-multiplexed and stored in the one-cell delay unit 2, the number of input / output terminals nf added to the spatial division optical switch module 1 is also n / ( L + 1) is sufficient, and if the capacity is to be expanded, it is advantageous to implement a large capacity optical switching module because it needs to be expanded in units of the optical switching subsystem 500.

As a result of analyzing the performance of the proposed optical switch, if the number of optical switching subsystem 500 is 4, one wavelength group is applied under the load condition of input traffic density = 0.9 and the cell loss condition of 1E-11. The number of variable wavelengths L = 4 used is required, and the dimension of the space division optical switch module 1 in the optical switching subsystem 500 is (n + n / 5) × (n + n / 5). Confirmed to be.

Claims (4)

In a self-routing optical switching system of a large capacity ATM optical switching system, The self-routing optical switching system consists of m optical switching subsystems with n input and output terminals in parallel, Each optical switching subsystem includes a space division optical switch module having n + nf input / output terminals; One cell delay means connected to the output terminal and the input terminal of the space division optical switch module by nf optical fiber lines; N input modules connected to input terminals of the space division optical switch module by n input optical fiber wires; A common buffer controller connected to the n input modules by bidirectional control signal lines, respectively; Unidirectional control signal line means for interconnecting the n input modules in a ring form; N wavelength group demultiplexers connected to an output terminal of the spatial division optical switch by n output optical fiber lines; And A distributed spatial / wavelength mixed structure using wavelength group multiplexing comprising for each optical switching subsystem a wavelength group demultiplexer in the m optical switching subsystems and n output modules connected by m output fiber lines. Optical switching system. The method of claim 1, Through the contention reclamation process over 2 timeslots, the unidirectional control signal line connected in a ring form for output re-competement between the n input modules and the common buffer controller connected to the bidirectional control signal line to the n input modules are processed. Select the wavelengths so that the wavelengths do not overlap in the same wavelength group, and store the input cells converted into wavelength multiplexes from the current state information of the CR packet in the one-cell retarder in the wavelength multiplexed state, and then output the spatial division optical switch module in the next time slot. By switching to terminals, the number of additional input / output terminals nf of the space division optical switch module to satisfy a certain cell loss condition is n / (L + 1), and the space division optical switch module is n + n / (L + 1). A distributed spatial / wavelength mixed optical switching system using wavelength group multiplexing, characterized in that it has a number of input and output terminals. The method of claim 1, The input module A content recreation controller and a wavelength controller connected to m input / output CR buses which are the common buffer controller and one-way control signal line; A cell buffer connected to an output terminal of the cell multiple part, a content recreation unit, and an input terminal of a wavelength controller by a data bus; A routing information inserter coupled to a data bus and a control bus at output terminals of the cell buffer, content recreation and wavelength controller, respectively; And A wavelength group multiple comprising a wavelength variable laser diode connected to an output terminal of a routing information inserter, an output terminal of a contention recreation and a wavelength controller, and an input terminal of the spatial division optical switch module, respectively, by data and a control bus. Distributed spatial / wavelength hybrid optical switching system. The method of claim 1, The output module m fixed filters connected to the output terminals of the m wavelength group demultiplexers through optical fiber lines, respectively; L photoelectric conversion means connected to the output terminal of each fixed filter by L optical fibers; And 10. A distributed spatial / wavelength mixed optical switching system using wavelength group multiplexing comprising an output buffer of mL photoelectric conversion means and an electrical buffer memory connected to a data bus at an input of the cell demultiplexer.