KR19980026748A - Photonic Switching System with Combined SD and WD Multiplex - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed ring contention resolution device of a spatial / wavelength mixed optical switching system for obtaining yields of several Tb / s or more in a large-capacity asynchronous transfer mode exchange.

In the self-routing optical switching system of a large-capacity optical ATM switching system, the present invention relates to a space division optical switch having n + nf input / output terminals, each of which includes nf optical fiber wires of an output terminal and an input terminal of the space division optical switch. 1 cell delay means connected, n input modules connected with n input optical fiber lines to the input terminals of the spatial division optical switch, one common buffer control means connected with the n input modules with bidirectional control signal lines, and the n inputs A unidirectional control signal line for interconnecting the modules in a ring form, and n output modules connected to the output terminal of the spatial split optical switch by one optical fiber line, respectively.

Description

Photonic Switching System with Combined SD and WD Multiplex

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

2 is an optical switch structure diagram using a distributed contention leisure line according to the present invention.

3 is a structural diagram of a space division optical switch module.

4 is a configuration diagram of an input module.

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

6 is a configuration diagram of an output module.

Explanation of symbols on the main parts of the drawings

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

3: input module 4: output module

5: common buffer controller 6: contention recreation bus

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial / wavelength hybrid optical switching system, and in particular, a large capacity capable of accommodating a large capacity subscriber video service such as high definition television (HDTV) distribution service as well as voice data and still image. In an asynchronous transfer mode (ATM) exchange, a distributed ring contention resolution device of a spatial / wavelength mixed optical switching system for obtaining a yield of several Tb / s or more. It is about.

In general, in implementing a NxN self-routing optical switch, the conventional wavelength division spatial switch can reduce the number of optical elements by about 50% in a single output stage by applying the contention retention process over two timeslots. However, 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 lasers. The disadvantage was the addition of a diode and a frequency variable filter.

And even in a conventional spatial / wavelength hybrid optical switch that switches by multiplexing multiple cells at different wavelengths on the internal link on the spatial switch, a constant cell loss rate is achieved when contention retention is applied over one time slot. There is a disadvantage that the variable wavelength range of the wavelength variable light source is too wide in order to ensure the accuracy, and the number of fixed filters required for the output stage and the size of the spatially divided optical switch are minimized even when the contention resolution over two timeslots is applied. Although there is an advantage that can be achieved, it is difficult to control the space division optical switch and expand the capacity of the exchange by applying the centralized contention contention.

In order to solve the above problems of the prior art, the present invention provides a constant by applying a contention leisure solution over two time slots using a distributed unidirectional serial bus in an input module of a basic spatial / wavelength mixed optical switch. In order to minimize the number of fixed filters and the size of the space split optical switch required at the output stage under cell loss conditions, the present invention provides a distributed contention resolution device that is easy to control the space split optical switch and expand the capacity of the exchanger. There is a purpose.

In order to achieve the above object, the present invention, in the self-routing optical switching system of a large-capacity optical ATM switching system, a space division optical switch having n + nf input and output terminals, respectively, to the output terminal and the input terminal of the space division optical switch 1 cell delay means connected by nf optical fiber wires: n input modules connected by n input optical fiber wires to the input terminal of the spatial division optical switch, and one common buffer control connected to the n input modules by bidirectional control signal lines, respectively Means, unidirectional control signal lines for interconnecting the n input modules in a ring form, and n output modules each connected by one optical fiber line to an output terminal of the spatial division optical switch.

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.

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

The cell multiplexer 200 implemented as an electronic circuit is connected to the optical disk system 100 using a data bus of a speed V (eg, 2.5 Gb / s), and the input cells are header-processed by the header converter 300. It is 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 a plurality of cell multiplexes 200, and then recognizes the destination address of each cell and has a corresponding destination address through a data bus having a speed of V. FIG. The cell demultiplexer 400 performs a self-routing switching function for outputting input cells.

And even when a plurality of input cells are simultaneously switched to the same incoming cell demultiplexer 400 at the same time, the optical switching system 100 should maintain a minimum cell loss rate so that the overall yield of the optical 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 3000, and then temporarily stores the cells in a buffer to avoid cell loss and stores the ATM cells v (eg Output at the speed of 155 Mb / s).

Therefore, the switching capacity of the ATM optical switching system depends on the structure and the switching method of the optical switching system 100. In the input module of the basic spatial / wavelength mixed optical switch, a distributed ring-type unidirectional serial bus is used for two time slots. By applying the contention reduction over, it is easy to control the space division optical switch and to expand the capacity of the exchange.

2 is a block diagram of the optical switching system 100 according to the present invention, and is easy to control the spatial division optical switching module 1 by applying the distributed ring-type contention retention, and thus the capacity increase is made in module units. Capacitance expansion is easy and the switch size and number of wavelength filters can be minimized.

As shown in FIG. 2, the optical switching system 100 includes a spatial division optical switch module 1, a one cell retarder 2, n input modules 3, n output modules 4, and a common buffer. It consists of the controller 5.

The input / output terminals of the spatial division optical switch module 1 are connected to the n input module 3 and the output module 4 in one direction with n input / output optical fiber wires, respectively, and the one cell retarder 2 is the spatial division optical fiber. The input and output terminals of the switch module 1 are interconnected with nf optical fibers, respectively.

The common buffer controller 5 is connected to 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 unidirectional control signal lines 6.

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. Contention recreation using the control signal line 6 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 6 is composed of one serial bus, and on the serial bus, the input module is input once in one time slot time of a cell into which n contention contention packets (CR packets) corresponding one-to-one to a destination address are input. (3) Cycle from 1 to n of input module (3).

Each 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 converts the CR packet having the destination address from the state information of the received CR packet from the previous input module 3 into the wavelength information to be used for wavelength conversion 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 over one cycle, each input module 3 replaces the current state information of the CR packet with the state information before 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 to 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.

In this way, the cells input to each input module 3 are selected in the wavelength groups λ1, λ2, ... λL so that the wavelengths do not overlap through the above contention recreation process.

When the number of input cells continues to be smaller than L when a plurality of cells entering the input terminal of the optical switch module 1 are continuously smaller than L, the previous time slot state in the corresponding wavelength group is subjected to contention recreation process. Since up to L can be converted to different wavelengths from the information, it is switched to the incoming output stage without any time delay in the wavelength multiplexed state.

However, in general, if the state information before one timeslot time of the CR packet is I and I cells are already waiting in the one 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 remaining input cells perform wavelength conversion differently from the current switching state information of the contention reduction process up to L, and these cells are the one-cell delayer (2). Space division optical switch module after receiving routing information including the address of 1 cell delay unit 2 from common buffer controller 5 so that it can be switched to the corresponding output stage after being stored for 1 timeslot time Send to

When the common buffer controller 5 receives the use request signal (including the destination address) of the one cell delay unit 2 from the input module 3, the common buffer controller 5 classifies the destination address, and the cells having the same destination output address in the optical switch module 1 are the same. For Rx, routing information including the address of the one cell delay unit 2 is sent to the corresponding input module 3 so that the wavelength can be stored in a multiplexed time slot.

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.

Each output module 4 receives up to L cells in a wavelength-multiplexed state through one optical fiber line from the output terminal of the optical switch module 1.

Each output module 4 receives up to L cells using L fixed filters (wavelength filter 1, wavelength filter 2, ... wavelength filter L) to select L cells.

Since each output module 4 is connected to the cell demultiplexer 400 with a data bus having a speed of V, each output module 4 is temporarily stored in a buffer to prevent cell loss, and then each cell is sequentially transferred to the cell demultiplexer 400. Output

Therefore, as in the present invention, the optical switching system 1000 is divided into a space-splitting optical switch module 1, one cell retarder 2, n input modules 3, n output modules 4, and a common buffer controller 5 The common buffer controller 5 is connected to n input modules 3 and bidirectional control signal lines, respectively, and the n input modules 3 are unidirectional control signal lines 6 so as to have a ring-shaped distributed structure. After connecting to each other and going through a contention recreation process over 2 timeslots, the control of the space division optical switch module 1 can be distributed and performed, so that the control of the space division optical switch is easy, and the capacity increase is also possible. 4) It is easy to expand capacity because it is composed of units.

Since the input cells have two switching opportunities, the required cell loss rate can be maintained while reducing the value of L, thereby reducing the number of wavelengths used for wavelength conversion, thereby minimizing the number of filters. In addition, 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.

FIG. 3 shows the arrangement of (n + nf) × (n + nf) in the device of the present invention which can easily control the space division optical switch and expand the capacity by applying the ring-type contention retention structure as described above. Fig. 1 shows the configuration of a space division optical switch module 1 and a one cell retarder 2 having a size.

As shown in FIG. 3, the space division optical switch module 1 of (n + nf) × (n + nf) includes n + nf optical space switches 10 and 11 and n + nf optical couplers 12. 13, and the one cell delay unit 2 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 to the output module 4 one-to-one with one output optical fiber line.

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 L input cells in the wavelength group λ1, λ2, ... λL, etc. are stored in the wavelength-multiplexed state for one time slot time, and are switched to the corresponding output stage at the next cell timeslot time. .

Similarly, the optical coupler 12 also wavelength-multiplies up to L input cells with different waves, and outputs them to the output module 4 through the output optical fiber line.

4 is a configuration diagram of an input module 3 that performs a contention recreation process and a 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 recreation 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 resolution and wavelength controller 33, and the input cell is sent to the routing information inserter 31. Is sent.

The contention recreation and wavelength controller 33 performs a contention recreation process over two timeslots using a CR packet as described above through one contention retention serial bus (CR bus), which is a unidirectional control signal line 6. 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.

In this way, after selecting one wavelength, the contention recreation and wavelength controller 33 increases the corresponding state information by the wavelength selection process by 1 and sends 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 the current switching is performed. When the wavelength is selected from the state information, one cell delay time should be stored in the one cell delay unit 2, so that the routing information inserter 31 receives the address of the one cell delay unit 2 from the common buffer controller 5. ) And the wavelength tunable laser diode 32 sends routing information and wavelength tunable 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 L different wavelengths to avoid wavelength duplication in the input module 3 performing the wavelength conversion function. The wavelength tunable laser diode 32 is formed from the contention leisure solution and the wavelength controller 33. One of the L wavelengths shown is designated.

6 is a configuration diagram of an output module 4 for receiving up to L cells input from an output terminal of the spatial division optical switch module 1.

As shown in FIG. 6, the output module 4 includes a fixed filter 40, a photoelectric converter 41, and a buffer memory 42.

The fixed filter 40 filters the wavelength multiplexed cells input through the optical fiber line connected to the optical switch module 1 to L wavelengths using the wavelength filters 1, 2, ... L.

The photoelectric converter 41 photoelectrically converts input cells wavelength-filtered from the fixed filter 40 to L optical fiber lines by using the L photoelectric conversion circuits.

The output module 4 receives and processes up to L cells at the same time, and temporarily stores them in the buffer memory 42 to prevent temporary cell loss. Output to the central portion (400).

As described above, according to the apparatus of the present invention, the optical switching system 100 includes a spatial division optical switch module 1, one cell retarder 2, n input modules 3, and n output modules 4 ), The common buffer controller (5), and the input / output terminals of the spatial division optical switch module (1) are connected to the n input modules (3) and the output module (4) in one direction by n input / output optical fiber lines, respectively, The one cell retarder 2 is connected to the input / output terminals of the spatial division optical switch module 1 by nf optical fibers, and then the unidirectional control signal line 6 connected in a ring form between the n input modules 3 and By using the common buffer controller 5 connected to the n input modules 3 by bidirectional control signal lines, the contention reduction process over two timeslots is distributed, thereby forming a spatial division optical switch module 1. Control of the optical space switches (10, 11) of the basic unit As a result, the control of the optical space switches 10 and 11 is easy, and the capacity increase is made in the input / output modules 3 and 4 and the optical space switch 10, thereby facilitating capacity expansion.

In addition, since input cells have two switching opportunities, it is possible to maintain the required cell loss rate while reducing L, thereby reducing the number of wavelengths and the number of filters used for wavelength conversion.

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.

For reference, in the proposed optical switch, under the load condition of input traffic density = 0.9 and the cell loss condition of 1 × 10-6, the number of variable wavelengths L = 4 used in the wavelength group is required, and the space division optical switch module (1 The dimension of) is (n + n / 5) × (n + n / 5).

Claims (3)

Magnetic Routing Optical Switching in High-Capacity ATM Optical Switching Systems In the system, 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; And Space / wavelength mixed optical switching system using a distributed structure ring-type contention retention structure, characterized in that consisting of n output modules connected to the output terminal of the spatial division optical switch by n output optical fiber lines. The method of claim 1, The input module A contention retention and wavelength controller connected to one input / output contention leisure line bus which is the common buffer controller and one-way control signal line; A cell buffer connected to a data bus of an output terminal of the cell multiple part, a contention recreation and an input terminal of a wavelength controller, respectively; A routing information inserter coupled to a data bus and a control bus at output terminals of the cell buffer, contention reduction, and wavelength controller, respectively; And Dispersion ring type cone, characterized in that consisting of a wavelength variable laser diode connected to the output terminal of the routing information inserter, the contention retention and the wavelength controller, the input terminal of the spatial division optical switch module, respectively by data and control bus Spatial / wavelength hybrid optical switching system with tension recreation. The method of claim 1, The output module L fixed filters connected to the output terminal of the spatial division optical switch module through one optical fiber line; L photoelectric conversion means connected to each output terminal of the fixed filter by an optical fiber line; A spatial / wavelength mixed optical switching system using a distributed ring-type contention solution, characterized in that it comprises an electric buffer memory connected to the output terminal of the photoelectric conversion means and the input terminal of the cell demultiplexer, respectively by a data bus.