JPH08293871A - Optical atm switch - Google Patents

Abstract

PURPOSE: To constitute a node of high speed and a large scale with few parts by respectively outputting a cell addressed to a next node among cells from an input light link and an input line, converting it to a light frequency and a cell addressed to an output line among them through a buffer. CONSTITUTION: The cells incoming from the input line and the input light link through an optical demultiplexer 10 are divided to cells addressed to the output line and cells addressed to the next node and outputted by 1-input and 2-output switchs 11-1 to 4. An output line buffer 12 inputs the cells addressed to the output line and outputs them to the output line. On the other hand, variable light frequency converters 13-1 to 4 input each cell addressed to the next node directly or through an input line buffer 14. Each converter 13 respectively converts the inputted cells to the cells of the light frequency corresponding to the address node by being controlled by a control circuit 16, and an optical connector 15 multiplex the cells and outputs them to the output light link. Thereby, cells execute routing in a node with little hard quantity and at high speed so that a large-scale node is easily constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical ATM switch for exchanging fixed length cells. In particular, a hypercube type optical AT using an arrayed waveguide diffraction grating type filter
The present invention relates to a node (switching element) configuration of an M switch.

[0002]

2. Description of the Related Art FIG. 4 shows the structure of a hypercube type ATM switch. In the figure, eight nodes are displayed with addresses 000 to 111 assigned to them. The nodes that accommodate the input / output lines are connected to each other by a hypercube network. In the hypercube network shown here, 8 nodes arranged in 3 (= log ₂ 8) dimensions compare 1 bit of each digit of the node address displayed in binary with the address of another node and 1 bit. Only the nodes that have different links have links. For example, node 000, node 001, node 010,
The nodes 100 are connected to each other (shown by thick lines in the figure).
The hypercube network has a self-routing function. Further, each node preferentially allocates a route to a cell having a short distance, and has a function of bypassing the cell when conflict occurs. Regarding Hypercube Network, read "Multic" by Reed and Fujimoto.
omputer Networks: Message-Based Parallel Process
ing ", 1987, The MIT Press", pages 17-18.

FIG. 5 shows the structure of a hypercube type optical ATM switch using an arrayed waveguide diffraction grating type filter (Japanese Patent Application No. 7-45835, "Hypercube type interconnection network"). In the figure, eight nodes are displayed with addresses 000 to 111 assigned to them. Each node accommodating the input / output line includes an in-node routing circuit 41, an optical multiplexer 42 and an optical demultiplexer 43.
Have. The input / output optical links of the nodes 000 to 111 are
Input / output port 0 of arrayed waveguide diffraction grating filter 60
~ 7 are connected in sequence. That is, nodes 000, 0
, 111, and the input ports 0, 1, 2, of the arrayed waveguide diffraction grating type filter 60.
..., 7 are connected. The output ports 0, 1, 2, ..., 7 of the arrayed-waveguide diffraction grating filter 60 and the node 00
The optical demultiplexers 43 of 0,001,010, ..., 111 are connected.

The input / output ports of the arrayed waveguide diffraction grating filter 60 and the optical frequency have a predetermined relationship. For example, the optical frequencies f0, f1, f input from the input port 0
The light of 2, ..., f7 are output ports 0,1,2,
..., 7 is output. The light of optical frequencies f0, f1, f2, f3, f4, f5, f6, f7 input from the input port 5 is output to the output ports 3, 4, 5, 6, 7, 7, 0, 1, 2 respectively. .

Here, in order to connect each node in a hypercube type, a predetermined optical frequency is used between the corresponding nodes. For example, node 000 and nodes 001, 010,
To connect 100, optical frequencies f1, f2, and f4 are used, respectively. When the optical frequency multiplexed light of the optical frequencies f1, f2, f4 is input to the input port 0 of the arrayed waveguide diffraction grating filter 60, the light of the optical frequencies f1, f2, f4 is output from the output ports 1, 2, 4 respectively. It is output (indicated by a thick line in FIG. 5) and sent to the corresponding node. Further, the optical frequencies f1, f4, and f6 are used to connect the node 101 and the nodes 001, 100, and 111, respectively. The optical frequency multiplexed light having the optical frequencies f1, f4 and f6 is the arrayed waveguide diffraction grating type filter 60.
When the light having the optical frequencies f1, f2, and f4 is input to the input port 5 of each of the output ports 4, 7, and 1 (see FIG. 5),
Are indicated by a thick line) and are sent to the corresponding nodes.

As described above, each node is connected through the arrayed waveguide diffraction grating type filter 60 and the optical frequency used in each node is selected, whereby routing by the optical frequency of the arrayed waveguide diffraction grating type filter 60 is performed. Each node can be connected in a hypercube type by utilizing the function. As a result, a plurality of optical links that are input and output to and from each node can be integrated into one input and output using the optical frequency multiplexing technique.

FIG. 6 shows a configuration example of the node 101 of the hypercube type optical ATM switch. In the figure, the cells (optical frequencies f1, f4, f6) on the input optical link connected to the output port 5 of the arrayed-waveguide diffraction grating filter 60 are demultiplexed by the optical demultiplexer 43, and are respectively converted into optoelectric converters. 44-1
Is converted into an electric cell by 4444-3 and input to the 1-input 2-output switch 45-1 to 45-3. Each 1-input 2-output switch outputs a cell to be sent to the output line to the output line buffers 46-1 to 46-3, and a cell to be sent to another node via the output optical link to the 4-input 3-output switch 47. Output. The cells of the input line are converted into electric cells by the photoelectric converter 44-4 and input to the 1-input 2-output switch 45-4. The 1-input 2-output switch 45-4 outputs the cells to be sent to the output line to the output line buffer 46-4,
The cells to be sent to the node via the output optical link are output to the input line buffer 48. The output cell of the input line buffer 48 is input to the 4-input / 3-output switch 47.

The cells input to the 4-input / 3-output switch 47 are output to the electro-optical converters 49-1 to 49-3 which convert the cells into optical-frequency cells corresponding to the destination node. The cells output from each electro-optical converter are multiplexed by the optical multiplexer 42 and sent to the output optical link. The cells of each of the output line buffers 46-1 to 46-4 are input to the electro-optical converter 49-4 via the selector 50, converted into cells of a predetermined optical frequency, and sent to the output line. 1-input 2-output switch 45-1 to 45-4 and 4-input 3-output switch 4
7 is switching-controlled by the control circuit 51.

In the configuration shown in FIG. 6, each switch, each buffer, selector and control circuit are all electric circuits. By using a matrix type optical switch instead of this electric switch, an opto-electric converter is not necessary, and a configuration using an optical frequency converter with a fixed oscillation optical frequency instead of the electro-optical converter is also possible.

[0010]

By the way, in the configuration shown in FIG. 6, there is a problem that the throughput of the node is limited by the band limitation of the electric switch. On the other hand, when the matrix type optical switch is used instead of the electric switch, the restriction on the signal band is loosened. However, with the current technology, it is difficult to integrate optical components such as optical switches, and as the number of input / output ports of an optical switch increases, the amount of hardware increases (generally proportional to (the number of input ports) x (the number of output ports)), It becomes difficult to operate the whole at high speed.

An object of the present invention is to provide an optical ATM switch whose scale can be easily expanded by using a node which enables high-speed in-node routing of a cell with a small amount of hardware.

[0012]

An optical AT according to claim 1,
The node of the M switch is connected to the input optical link and has an optical demultiplexer having a fixed demultiplexing characteristic, and is connected to each output port and the input line of the optical demultiplexer and outputs to the output line or the output optical link. Multiple 1 inputs 2 that switch and output cells
An output optical switch, an input line buffer, a plurality of variable optical frequency converters for inputting cells to be sent to an output optical link, converting them to specified optical frequencies and outputting them, and frequency multiplexing each cell for output optical output. Optical coupler for sending to link, output line buffer for sending cells to output line one by one to output line, 1-input 2-output optical switch, variable optical frequency converter based on routing information of cells And a control circuit for controlling each output optical frequency and the extraction of cells from the input line buffer.

The node of the optical ATM switch according to the present invention comprises an input line buffer, a first optical multiplexer for frequency-multiplexing an output cell of the input line buffer and a cell of the input optical link, and a first optical multiplexer. Connected to the output device, outputs at most one wave to the first output port, outputs the wave of the remaining optical frequency to the second output port, and changes the demultiplexing characteristic to each output port. Demultiplexer, a plurality of fixed optical frequency converters for converting the cells output from the first output port of the variable demultiplexer to predetermined optical frequencies, and cells output from the plurality of fixed optical frequency converters A second optical multiplexer for frequency-multiplexing and transmitting to the output optical link, and an output line buffer for inputting cells output from the second output port of the variable demultiplexer and sending them to the output line one by one , Based on cell routing information And an output optical frequency of the output port of the variable demultiplexer, and a control circuit for controlling the removal of cells from the input line buffer.

[0014]

In the node of the optical ATM switch according to claim 1, of the cells arriving from the input optical link and the input line, the one addressed to the next node is converted to the corresponding optical frequency by the variable optical frequency converter. It is sent to the output link, and the one addressed to the output line is sent to the output line via the output line buffer.

In the node of the optical ATM switch according to the second aspect, the cells arriving from the input optical link and the input line are multiplexed and input to the variable demultiplexer, and the one addressed to the next node corresponds to that node. The fixed optical frequency converter converts it to a predetermined optical frequency and sends it to the output link, and the one addressed to the output line is sent to the output line via the output line buffer.

[0016]

【Example】

(First Embodiment) FIG. 1 shows a first embodiment of a node 101 which constitutes an optical ATM switch of the present invention. In the figure,
The node 101 has an arrayed waveguide diffraction grating type filter 6
An input / output optical link connected to the 0 input / output port and an input / output line are accommodated. The optical demultiplexer 10 connected to the input optical link has a fixed demultiplexing characteristic, and has a number of output ports equal to the dimension number (here, 3) of the hypercube network. 1-input 2-output optical switches 11-1 to 11-3 are connected to each output port of the optical demultiplexer 10, one output of which is connected to the output line buffer 12, and the other output is variable optical frequency conversion. 13-1 to 13-3. 1-input 2-output optical switch 11-4 for input line
Are connected to the output line buffer 12, and the other output is connected to the input line buffer 14. The output of the input line buffer 14 is connected to the variable optical frequency converter 13-4. The output of each variable optical frequency converter is connected to the optical coupler 15, and its output is connected to the output optical link. The output of the output line buffer 12 is connected to the output line. The control circuit 16 uses the one-input / two-output optical switches 11-1 to 11-4 based on the cell routing information.
And the output optical frequencies of the variable optical frequency converters 13-1 to 13-4 and the extraction of cells from the input line buffer 14.

On the input optical link connected to the output port 5 of the arrayed waveguide grating filter 60, the optical frequency
The cells f1, f4, and f6 are multiplexed. These cells are demultiplexed by the optical demultiplexer 10, and the cells to be sent to the output line via the 1-input 2-output switches 11-1 to 11-3 are input to the output line buffer 12 to output the output optical link. The cells to be transmitted to other nodes via the respective nodes are input to the variable optical frequency converters 13-1 to 13-3. As for the cells of the input line, the cells to be sent to the output line via the 1-input / 2-output switch 11-4 are input to the output line buffer 13, and the cells to be sent to the node via the output optical link are via the input line buffer 14. And is input to the variable optical frequency converter 13-4.

The cells input to the variable optical frequency converters 13-1 to 13-4 are converted into optical frequency cells corresponding to the destination node, respectively, and multiplexed by the optical coupler 15 to form an output optical link. Sent out. The control of the cell including the method of determining the transfer destination node is described in, for example, Japanese Patent Application No. 1-11412.
The control circuit 16 executes by the method shown in 6 (self-routing speech path). The variable optical frequency converter can be realized, for example, by a method of once converting an optical signal into an electric signal and then converting it into a predetermined optical frequency using a variable optical frequency light source such as a distributed Bragg reflection type semiconductor laser with multiple electrodes. .

The cells of the output line buffer 12 are sent out one by one on the output line. The output line buffer 12 is provided with an electric buffer corresponding to the input port as shown in FIG.
The output may be controlled by a selector. Also, after optical frequency multiplexing at the entrance of the output line buffer,
The frequency multiplex buffer described in the literature ("Optical ATM switch using frequency multiplex type output buffer", 1994 IEICE Spring National Convention, paper number B-558) may be used.

In this embodiment, the input line buffer 14
However, if there is a vacancy in the optical frequency on the output optical link, multiple cells are taken out from the input line and each variable optical frequency converter converts them to an appropriate optical frequency. Very good. By allowing a plurality of cells to be taken out, the number of input buffers can be reduced.

(Second Embodiment) FIG. 2 shows an optical ATM of the present invention.
The 2nd Example of the node 101 which comprises a switch is shown.
In the figure, a node 101 accommodates an input / output optical link connected to the input / output port of the arrayed waveguide diffraction grating type filter 60 and an input / output line. The input line buffer 21 is connected to the input line. The output of the input line buffer 21 and the input optical link are connected to an optical multiplexer 22 having a fixed multiplexing characteristic. The output of the optical multiplexer 22 is connected to the variable demultiplexer 23 whose demultiplexing characteristic to each output port is variable. The variable demultiplexer 23 has the same number of first output ports and second output ports as the number of dimensions of the hypercube network (here, 3), and each of the first output ports has at most one wave. Then, the wave of the remaining optical frequency is output to the second output port. The fixed optical frequency converter 24-1 is connected to the first output port of the variable demultiplexer 23, respectively.
~ 24-3 are connected. The output of each fixed optical frequency converter is connected to the optical multiplexer 25 having a fixed multiplexing characteristic, and its output is connected to the output optical link. An output line buffer 26 is connected to the second output port of the variable demultiplexer 23, and its output is connected to the output line. Control circuit 27
Is a variable demultiplexer 23 based on the routing information of the cell.
Output optical frequency of each output port of and input line buffer 2
Controls cell removal from 1.

On the input optical link connected to the output port 5 of the arrayed waveguide grating filter 60, the optical frequency
The cells f1, f4, and f6 are multiplexed. These cells are
The optical multiplexer 22 carries out optical frequency multiplexing with the output cell of the input line buffer 21, and inputs to the variable demultiplexer 23. In the variable demultiplexer 23, the cells to be sent to the output line are output from the second output port to the output line buffer 26. Further, the cell to be sent to another node via the output optical link is output from the first output port to the fixed optical frequency converter for converting the optical frequency corresponding to the transfer destination node. The control of the cell including the method of determining the transfer destination node is executed by the control circuit 27 by the same method as in the first embodiment. Further, the relationship between the transfer destination node and the optical frequency on the output link can be determined from the relationship between the characteristics of the arrayed waveguide diffraction grating filter 60 and the connection between the nodes in the hypercube network. The fixed optical frequency converter can be realized by, for example, a method in which an optical signal is once converted into an electrical signal and then converted into a predetermined optical frequency using an appropriate optical frequency light source.

The cells of the output line buffer 26 are sent out one by one on the output line. The output line buffer 26 may have a structure in which an electric buffer corresponding to the optical frequency is provided as shown in FIG. 6 after the cell is demultiplexed at the entrance and the output is controlled by the selector. Further, the frequency multiplexing buffer described in the document shown in the first embodiment may be used in the optical frequency multiplexed state.

In the present embodiment, as in the first embodiment, if there is a vacancy in the optical frequency on the output optical link, a method of taking out a plurality of cells from the input line can be adopted. In that case, each cell is converted to an appropriate optical frequency and then input to the optical multiplexer 22, and the variable demultiplexer 23 shown in FIG. 2 is configured to handle 5 or more waves instead of 4 waves.

FIG. 3 shows a configuration example of the variable demultiplexer 23.
The configuration shown here is based on the literature ("Photonic highway Switch usi
ng PLC ring resonators ", 19th ECOC International Conference Proceedings
WeP10.2, pp.545-548, 1993). In the figure, variable frequency selection circuits 31-1 to 31-3 using ring resonators are connected in cascade. Each variable frequency selection circuit has a frequency selection control electrode 32 in the ring resonator and is configured to set an optical frequency to be selected by a control signal from the control circuit 27. In the example shown here, cells with optical frequencies f1, f4, f6, fi are input, and at most one wave of optical frequencies f1, f4, f6, fi is taken out to the first output port by each variable frequency selection circuit. , The remaining optical frequency waves are extracted at the second output port.

[0026]

As described above, the optical ATM of the present invention
The switch can realize high-speed intra-node routing of a cell with a small amount of hardware by utilizing the optical frequency routing function for the intra-node routing of the cell arriving at the node. That is, since the number of components that perform optical frequency conversion is only proportional to the number of input / output ports of the node, it is possible to configure a node with a small number of components, and it is possible to configure a large-scale node relatively easily. it can. Thereby, a large-scale optical ATM switch can be easily realized.

[Brief description of drawings]

FIG. 1 is a node 1 constituting an optical ATM switch of the present invention.
The block diagram which shows the 1st Example of 01.

FIG. 2 is a node 1 constituting the optical ATM switch of the present invention.
The block diagram which shows the 2nd Example of 01.

FIG. 3 is a block diagram showing a configuration example of a variable demultiplexer 23.

FIG. 4 is a diagram showing a configuration of a hypercube type ATM switch.

FIG. 5 is a block diagram showing a configuration of a hypercube type optical ATM switch using an arrayed waveguide diffraction grating type filter.

FIG. 6 is a node 1 of a hypercube type optical ATM switch.
The block diagram which shows the structural example of 01.

[Explanation of symbols]

 10 optical demultiplexer 11 1 input 2 output optical switch 12 output line buffer 13 variable optical frequency converter 14 input line buffer 15 optical coupler 16 control circuit 21 input line buffer 22, 25 optical multiplexer 23 variable demultiplexer 24 fixed Optical frequency converter 26 Output line buffer 27 Control circuit 31 Variable frequency selection circuit 32 Frequency selection control electrode 60 Arrayed waveguide diffraction grating type filter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H04Q 3/52 101 H04B 9/00 T

Claims (2)

[Claims] 1. An array in which a node accommodating an ATM input / output line and an input / output port of an arrayed waveguide diffraction grating type filter are connected via an input / output optical link, and an optical frequency used for each node is connected. The input and output ports of the waveguide grating filter are set so as to satisfy the connection relationship of the hypercube network, and each node outputs based on the routing information for the cells input from the input optical link and input line. In an optical ATM switch that determines a destination and performs control to divert to another node or to wait in a buffer when contention occurs, the node is connected to the input optical link, and has a dimensionality of a hypercube network. An optical demultiplexer having a fixed demultiplexing characteristic with a number of output ports equal to, and each output port of the optical demultiplexer and the input line. A plurality of 1-input 2-output optical switches connected to the output line or the output optical link to switch and output cells, and output from the input line to the output optical link via the 1-input 2-output optical switch An input line buffer for accumulating cells, and a cell sent from the plurality of 1-input 2-output optical switches or the input line buffer to the output optical link,
A plurality of variable optical frequency converters each converting to a predetermined optical frequency and outputting, and an optical coupler that frequency-multiplexes cells output from the plurality of variable optical frequency converters and sends out to the output optical link, An output line buffer for inputting cells sent from the plurality of one-input two-output optical switches to the output line and sending the cells one by one to the output line, and a plurality of the one-input two-input units based on the routing information of the cells.
An optical A comprising an output optical switch, output optical frequencies of the plurality of variable optical frequency converters, and a control circuit for controlling cell extraction from the input line buffer.
TM switch. 2. An array in which a node accommodating an ATM input / output line and an input / output port of an arrayed waveguide diffraction grating type filter are connected via an input / output optical link, and an optical frequency used for each node is connected. The input and output ports of the waveguide grating filter are set so as to satisfy the connection relationship of the hypercube network, and each node outputs based on the routing information for the cells input from the input optical link and input line. In an optical ATM switch that determines a destination and performs control to divert to another node or to make a buffer wait when a conflict occurs, the node includes an input line buffer for accumulating cells arriving from the input line. A first optical multiplexer for frequency-multiplexing the output cell of the input line buffer and the cell of the input optical link; and a first optical multiplexer connected to the first optical multiplexer. Has a first output port and the second output ports the number of which is equal to the number of dimensions of the hypercube network, at most to the first output port 1
A variable demultiplexer that outputs each wave, outputs a wave of the remaining optical frequency to the second output port, and has a variable demultiplexing characteristic to each output port; and a first demultiplexer of the variable demultiplexer. A plurality of fixed optical frequency converters for converting the cells output from the output ports into predetermined optical frequencies, and the cells output from the plurality of fixed optical frequency converters are frequency-multiplexed and sent to the output optical link. A second optical multiplexer, an output line buffer for inputting cells output from the second output port of the variable demultiplexer, and sending them to the output line one by one, and based on the routing information of the cells, An optical ATM switch, comprising: an output optical frequency of each output port of the variable demultiplexer; and a control circuit for controlling cell extraction from the input line buffer.