JPH0752976B2 - Optical switch network control system - Google Patents

Description

The present invention relates to a control system for an optical switch network such as an optical switch.

(Prior Art) Optical fiber transmission technology has rapidly advanced in recent years and its application range is expanding more and more, and an optical switching system for switching an optical signal as an optical signal is being studied aiming at a more advanced system. It is desirable that the optical switching system is capable of not only one-to-one communication exchange such as a videophone, but also one-to-N communication exchange for distributing a television signal or the like to a plurality of terminals. If the optical switch network in the optical switching system has not only the function of connecting one input line and one output line, but also the function of branch connection connecting one input line and a plurality of output lines,
Exchange of such 1-to-N communication becomes possible. Conventionally, as an optical switch network that can be branched and connected, the Technical Report of the Institute of Electronics and Communication Engineers of Japan, Technical Report, Vol. 85, No. 68, SE85-33, pages 25-30
There is one described in. FIG. 4 shows a conventional 4-input 4-output optical switch network. Entry line 40
The optical signal input from 1 is split into 4 by the splitter 411,
Selection switches 43 are selected by the optical waveguides 415, 416, 417 and 418, respectively.
It is sent to 1,432,433,434. Similarly, the optical signals input from the input lines 402, 403, 404 are similarly branched by the branching devices 412, 413, 414 and sent to the selection switches 431, 432, 433, 434, respectively. The selection switch 431 selects one of the output optical signals of the branchers 411, 412, 413, 414 input by the optical waveguides 415, 419, 420, 421 and connects it to the output line 441. This will allow you to enter lines 401, 402, 4
One of the optical signals input to 03, 404 can be sent to the output line 441. Similarly, with the selection switches 432, 433, 434, branch switches
Select one of the output optical signals of 12,413,414 and output line 442,44
By connecting to 3,444, one of the optical signals input to the input lines 401, 402, 403, 404 can be sent to the output lines 442, 443, 444. Further, for example, if the selection switches 431 and 432 select the output optical signal of the branching device 411, the input lines 4 and 4 can be simultaneously input to the output lines 441 and 442.
The optical signal input to 01 is transmitted, and branch connection is realized.

FIG. 5 shows the selection switches 431,432,433,434 in FIG.
It is a figure which shows the specific example of. In the figure optical switch 505,50
7,509 controls 1 from 2 inputs by controlling voltage V
It operates as a 2 × 1 optical switch that selectively outputs one.
Further, the optical switch 511 operates as an optical switch that interrupts an optical signal that passes by controlling the voltage. The optical switch 505 selects the optical signal from one of the input optical waveguides 501 and 502 and sends it to the optical waveguide 506, and the optical switch 507 selects the optical signal from one of the input optical waveguides 503 and 504 and selects the optical waveguide 5
Send to 08. The optical switch 509 further selects an optical signal from one of the optical waveguides 506 and 508 and sends it to the optical waveguide 510. Therefore, any one of the optical signals input from the input optical waveguides 501, 502, 503, 504 is selectively transmitted to the optical waveguide 510.
The selected optical signal is sent to the output optical waveguide 512 if the optical switch 511 is in the conductive state, and is not sent if the optical switch 511 is in the disconnected state.

The optical branching devices 411 to 414 in FIG. 4 are technical report 86, Optical and Quantum Electronics Research Group of the Institute of Electronics and Communication Engineers OQE84-
107 An optical fiber type distribution circuit described on pages 81 to 87 or a plurality of branched optical switches can be used.
FIG. 6 is a diagram showing a configuration of a branching device using a plurality of branching optical switches. In FIG. 6, optical switches 602, 60
5,606 is in a state where a constant voltage of Vm is applied and an optical signal input from one incident end is branched to the other two outgoing ends with an equal amount of light. Therefore, the optical signal input from the input optical waveguide 601 is bisected by the optical switch 602 and is output to the optical waveguides 603 and 604. The optical signal emitted to the optical waveguide 603 is further bisected by the optical switch 605 and emitted to the output optical waveguides 607 and 608. The optical signal output to the optical waveguide 604 is divided into two equal parts by the optical switch 606 and output to the output optical waveguides 609 and 610. Therefore, the optical signal input from the input optical waveguide 601 is divided into four equal parts and the output optical waveguide 6
It is emitted to 07,608,609,610.

FIG. 7 shows the optical switches 505, 507, 509, 511 in FIG.
6 shows an example of the structure and characteristics of the optical switches 602, 605 and 606 in FIG.

The optical switch is composed of optical waveguides 702 and 703 formed close to each other on an optical crystal 701 having an electro-optical effect as shown in FIG. 7 (a). At this time, the incident light 1 of the light amount Pin is transmitted from one incident end 710 of the optical waveguide 702 to the optical waveguide 703.
When the incident light 2 of the light quantity Pin is also applied from one of the incident ends 711 to change the voltage V between the electrodes 704 and 705 on the optical waveguides 702 and 703, the incident light included in the optical signal output from the other end faces 707 and 708 of the optical waveguides 702 and 703 is changed. The light amounts of 1 and incident light 2 change. FIG. 7B shows the light amount 720 of the incident light 2 and the light amount 721 of the incident light 1 included in the optical signal output from the end face 707 with respect to the voltage V. FIG. 7C shows the light amount 722 of the incident light 1 and the light amount 723 of the incident light 2 included in the optical signal output from the end surface 708 with respect to the voltage V. When V = Vl, most of the incident light 1 is from the exit end 707,
A small amount is output as crosstalk from the output end 708,
Most of the incident light 2 is output from the output end 708, and a small amount is output from the output end 707 as crosstalk. This state is called a bar state. When V = Vh, most of the incident light 1 is emitted from the emission end 708, and a small amount is crosstalk as emission end 707.
Most of the incident light 2 is output from the output end 707,
A small amount is output from the output end 708 as crosstalk.
This state is called a cross state.

Optical switches 505, 507 and 509 in FIG.
When two optical signals are applied to the input end and the control voltage Vl or Vh is applied, the optical signal input from the output end 707 to the input end 710 at V = Vl is obtained, and the optical signal input to the input end 711 at V = Vh. Is operating as a 2 × 1 switch. Further, the optical switch 511 in FIG. 5 makes V = V from the emitting end 707 when an optical signal is made incident on the incident end 710 and a control voltage Vl or Vh is applied.
In l, an optical signal is obtained, and in V = Vh, it operates as an optical switch that disconnects the optical signal.

In FIG. 7 (a), only the incident light 1 with the light amount Pin is incident end 7
When the voltage V is input to the output terminal 10 and the output light amount from the output terminal 707 is changed to 721 in FIG.
The output light quantity from 08 changes like 722 in FIG. 7 (c). When V = Vm, the amount of light output from the emission ends 707 and 708 is 1/2 Pin. This state is called a branch state. The optical switches 602, 605 and 606 in FIG. 6 are in a branched state in which the voltage Vm is applied.

(Problems to be Solved by the Invention) Since the optical switch networks 411, 412, 413, 414 are used in the conventional optical switch network shown in FIG.
There is a problem that the accumulation of crosstalk caused by 31.432,433,434 is large. FIG. 8 is a diagram showing an example of accumulation of crosstalk, in which the same numbers as those in FIG. 4 represent the same components as in FIG. In this case, the optical signal from the incoming line 401 is not connected to any outgoing line, the optical signal from the incoming line 402 is connected to the outgoing line 443, the optical signal from the incoming line 403 is branched and connected to the outgoing lines 441 and 442, and the incoming line is The optical signal from 404 shall be connected to outgoing line 444. In the selection switch 431, the optical signal guided by the optical waveguide 801 indicated by the solid line from the branching device 413 is sent to the outgoing line 441 via the optical switches 802, 803, 804 in the bar state. At this time, unnecessary optical signals from the branching devices 411, 412, 414 guided by the optical waveguides 805.806, 807 shown by the broken lines are also input to the selection switch 431, which causes crosstalk. Also in the other selection switches 432, 433, 434, in addition to the original optical signal guided by the optical waveguides shown by the solid line in FIG. 8, unnecessary optical signals guided by the three optical waveguides shown by the broken lines are input. Therefore, crosstalk occurs.

As the number of input / output lines of the optical switch network increases, the number of input terminals of the selection switch increases, and along with that, a large number of unnecessary optical signals are input and crosstalk is accumulated. Crosstalk causes noise for analog signals and code errors for digital signals, and it is necessary to reduce crosstalk in order to realize a large-scale optical switch network. It is an object of the present invention to provide an optical switch network control system with small crosstalk even when branch connection is made in a large-scale optical switch network.

(Means for Solving the Problems) An optical switch network control method provided by the present invention to solve the above-mentioned problems is a plurality of one-input / two-output vertically connected in a tree-like manner with one input line as a base point. M 1-input N-output distribution switches composed of optical switches and 1
One output of each of the M distribution switches is connected to each of M inputs composed of a plurality of 2-input 1-output optical switches that are vertically connected in a tree-like structure with one output line as a base point. In an M-input N-output optical switch network including at least an M-input 1-output selection switch, a plurality of 1-input 2-output optical switches in the 1-input N-output distribution switch outputs the input light at a light quantity ratio according to a control voltage. It is possible to branch to one output, and when one input line is branched and connected to a plurality of output lines, two output light quantity ratios are provided to all the one-input and two-output optical switches in the distribution switch to which the one input line is connected. It is characterized by giving equal control voltages.
Further, the optical switch network control system provided by the present invention is configured by a plurality of 1-input 2-output optical switches which are vertically connected in a tree-like structure with one input line as a base point.
One input of each of the M distribution switches to M inputs composed of an input N output distribution switch and a plurality of 2-input 1-output optical switches cascade-connected in a tree shape with one output line as a base point. In the M-input N-output optical switch network including at least N M-input 1-output selection switches connected to each other, a plurality of 1-input 2-output optical switches in the 1-input N-output distribution switch are responsive to a control voltage. It is possible to split the input light into two outputs with different light intensity ratios.
When one input line is branched and connected to a plurality of output lines, a control in which two output light amount ratios are equal to one input / two output optical switch which is a branch point of an optical signal path in the distribution switch to which the one input line is connected It is characterized by applying a voltage.

(Operation) In the present invention, a distribution switch is used instead of the branch device of the conventional optical switch network as described above, and only the distribution switch to which the optical signal to be branched and connected is input is used as the branch device. As a result, the number of unnecessary optical signals input to the selection switch can be reduced, and the occurrence of crosstalk can be reduced. Furthermore, by using only the optical switch that is the branch point in the distribution switch to which the optical signal for branch connection is input as the branch state, the number of unnecessary optical signals input to the selection switch can be further reduced, and crosstalk It is possible to further reduce the occurrence.

(Example) Hereinafter, the Example of this invention is described with reference to drawings.
FIG. 1 is a diagram showing a configuration of an embodiment of the present invention and shows a 4-input 4-output optical switch network. FIG. 1 has the same configuration as that of FIG. 4 except that distribution switches 111, 112, 113, 114 are used instead of the branching devices 411, 412, 413, 414 in the conventional 4-input 4-output optical switch network shown in FIG. The attached parts represent the same components as in FIG. The distribution switch 111 includes an optical switch 121 to which the optical signal from the incoming line 401 is input and an optical switch 121.
Of the optical switches 122 and 123 to which the respective two outputs are input. The outputs of the optical switches 122 and 123 are connected to the optical waveguides 415 to 418, respectively. The optical switches 121 to 123 are the same as those shown in FIG. Like the distribution switch 111, the distribution switches 112 to 114 are each composed of three optical switches.

FIG. 2 is a diagram for explaining the operation of the first embodiment of the present invention, in which the same numbers as those in FIG. 1 represent the same components as in FIG. At this time, similarly to the operation example of the conventional optical switch network of FIG. 8, the optical signal from the input line 401 is not connected to any output line, and the optical signal from the input line 402 is output line 4.
The optical signal from the incoming line 403 is connected to the outgoing line 441 and 442.
The optical signal from the incoming line 404 is connected to the outgoing line 444. The optical signal from the incoming line 401 is input to the selection switch 433 via the optical switches 201 and 202 in the bar state and the optical waveguide 203. In FIG. 2, among the optical waveguides between the distribution switch selection switches, those not passing an optical signal are not shown, and only the optical waveguide 203 is shown from the distribution switch 111. In order to connect the optical signal from the incoming line 402 to the outgoing line 443, the distribution switch 112 is connected to the incoming line 402.
And the optical waveguide 204 are connected, and the selection switch 433 is the optical waveguide 20.
4 and outgoing line 443 need to be connected. Therefore, the optical switches 205 and 206 in the distribution switch 112 are controlled to the bar state, the optical switches 207 and 209 in the selection switch 433 are controlled to the bar state, and 208 is controlled to the cross state. Since the optical signal from the incoming line 403 is branched and connected, the optical switches 215, 216 and 217 in the distribution switch 113 are connected.
Control all branches. Then, the optical signal from the incoming line 403 is branched into four and sent to the optical waveguides 218, 219, 220 and 221. The selection switch 431 outputs the optical signal from the incoming line 403 added via the optical waveguide 218 to the outgoing line 441 by controlling the optical switches 225, 226, 227 to the bar state. Similarly, in the selection switch 432, by controlling the optical switches 228, 229, and 230 in the bar state, the input line 4 added via the optical waveguide 219 is added.
The optical signal from 03 is output to the output line 442. In order to connect the optical signal from the incoming line 404 to the outgoing line 444, the distribution switch 114 has the incoming line.
It is necessary to connect 404 and the optical waveguide 235, and the selection switch 434 should connect the optical waveguide 235 and the outgoing line 444. Therefore, the optical switch 236 in the distribution switch 114 is controlled to the bar state, the optical switch 237 is controlled to the cross state, the optical switch 238 in the selection switch 434 is controlled to the cross state, and the optical switches 239 and 240 are controlled to the bar state.

In the above connection, the selective switch 431 does not add unnecessary optical signals other than the optical signals to be originally connected to the optical switch 225 from the optical waveguide 218, and thus crosstalk does not occur. Also in the selection switch 432, an unnecessary optical signal other than the optical signal to be originally connected to the optical switch 228 from the optical waveguide 219 is not added and crosstalk does not occur. In the selection switch 433, the optical waveguide 204
In addition to the optical signals to be originally connected to the optical switch 207 from the optical switch 207, two unnecessary optical signals are input via the optical waveguides 203 and 204. In the selection switch 434, only one unnecessary optical signal is input via the optical waveguide 221 in addition to the optical signal to be originally connected from the optical waveguide 235 to the optical switch 238. In the conventional switch network, as shown in FIG. 8, three unnecessary optical signals are input to all the selection switches 431 to 434, whereas in the first embodiment of the present invention, the selection switch 431. The number of unnecessary optical signals added to ~ 434 can be reduced and crosstalk can be significantly reduced.

FIG. 3 is a diagram for explaining the operation of the second embodiment of the present invention, and the connection of the incoming line and the outgoing line is the same as the diagram for explaining the operation of the first embodiment of the present invention in FIG. Is. The same reference numerals as those in FIG. 2 represent the same components as those in FIG. Further, the distribution switches 111, 11 other than the distribution switch 113
The control of the optical switches in 2,114 and the optical switches in the selection switches 431 to 444 is the same as in FIG. Distribution switch
In 113, an optical waveguide 218 connected to the selection switches 431, 432,
The optical switch 215 is in a crossed state so that the optical signal from the incoming line 403 is branched to only 219, and the optical switch 216, which is a branch point.
Controls the branch state.

As a result, unnecessary optical signals input to the selection switches 433 and 434 in the first embodiment of the present invention shown in FIG. 2 via the optical waveguides 220 and 221 are not generated, and crosstalk generated in the selection switch 433 is reduced. At 434, crosstalk no longer occurs.

(Effects of the Invention) As described above, according to the present invention, it is possible to reduce the crosstalk generated in the optical switch network and to realize a large-scale optical switch network.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the first embodiment of the present invention, and FIG. 3 is an operation of the second embodiment of the present invention. 4 is a diagram showing the configuration of a conventional optical switch network, FIG. 5 is a diagram showing a specific example of the selection switches 431 to 434 in FIG. 4, and FIG. 6 is a diagram in FIG. FIG. 7 is a diagram showing an example of the branching devices 411 to 414, FIG. 7 is an optical switch 505 in FIG. 5 and FIG.
FIG. 8 is a diagram showing an example of the structure and characteristics of 507, 509, 511, 602, 605 and 606, and FIG. 8 is a diagram for explaining the operation of the conventional optical switch network of FIG. In the figure, 111-114 are distribution switches, 121-123, 201, 2
02,205 ~ 209,215 ~ 217,225 ~ 230,236 ~ 240,505,507,50
9,511,602,605,606,802 ~ 805,809 ~ 811,814,822 ~ 824,8
27,829-831,834 are optical switches, 411-414 are branching devices, 431
434 is a selection switch, 701 is an electro-optic crystal, and 704 and 705 are electrodes.

Claims (2)

[Claims] 1. A M-input 1-output N-output distribution switch composed of a plurality of 1-input 2-output optical switches that are vertically connected in a tree shape with one input line as a base point, and a tree with one output line as a base point. N input-one-output selection switches, each of which has one input of the M distribution switches connected to each of the M inputs composed of a plurality of two-input one-output optical switches connected in cascade In the optical switch network of M input N output including at least, a plurality of 1 input 2 output optical switches in the 1 input N output distribution switch can branch the input light into two outputs at a light quantity ratio according to a control voltage. When one input line is branched and connected to a plurality of output lines, a control voltage for equalizing two output light quantity ratios is given to all the one-input and two-output optical switches in the distribution switch to which the one input line is connected. Optical switching network control method, characterized in that. 2. A M-input 1-output N-output distribution switch composed of a plurality of 1-input 2-output optical switches cascade-connected in a tree pattern with one input line as a base point, and a tree with one output line as a base point. N input-one-output selection switches, each of which has one input of the M distribution switches connected to each of the M inputs composed of a plurality of two-input one-output optical switches connected in cascade In the optical switch network of M input N output including at least, a plurality of 1 input 2 output optical switches in the 1 input N output distribution switch can branch the input light into two outputs at a light quantity ratio according to a control voltage. When one input line is branched and connected to a plurality of output lines, two output light quantity ratios are equal to one input and two output optical switches which are branch points of the optical signal path in the distribution switch to which the one input line is connected. Optical switching network control method, characterized by providing a control voltage that.