JPH04260295A - Wavelength division/time division composite optical exchanger - Google Patents

Abstract

PURPOSE:To eliminate the need for an optical switch to read an optical signal stored in an optical memory element in the optical exchange implements talking connection between input and output optical highways subjected to wavelength division and time division multiplex. CONSTITUTION:Variable wavelength selection elements 130-135 select an optical signal of a desired wavelength from an incident optical signal subject to wavelength division and time division multiplex and sends the signal to optical memory elements 140-145. The optical memory elements 140-145 store an optical signal of a desired time slot from an output optical signal from the variable wavelength selection elements 130-135. Then the optical signal stored in the optical memory elements 140-145 in a desired time slot is converted into an optical signal of a specific wavelength and radiates externally. Through the constitution above, a read optical switch having been required for a conventional exchange is not required and number of active optical components is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switching system that exchanges signals as they are between wavelength-division multiplexed and time-division multiplexed input optical signals and output optical signals.

0002

[Prior Art] Optical communications using optical fibers as transmission paths are
Optical fibers are expected to be widely used in the future because they have advantages such as being able to transmit a large amount of information due to their wide band and not being affected by induced noise. The switch used in this optical communication is preferably an optical switch that can exchange optical signals in the optical domain. Such optical switching equipment includes, for example, Suzuki et al. ``Study of wavelength division/time division composite optical communication paths'' (IEICE Switching Study Group Proceedings SE8).
7-146 pp. 91-96, 1987), an optical switching system has been proposed in which optical signals are exchanged by exchanging wavelengths and time slots between wavelength-division multiplexed and time-division multiplexed input and output optical signals.

FIG. 7 is a diagram showing such a conventional wavelength-division/time-division composite optical switching system, in which the wavelength-division multiplexing degree is 2 and the time-division multiplexing degree is 3. input optical highway 10
The wavelength-divided and time-division multiplexed optical signals on 0 are sent to optical splitters 120 and 121 via optical splitter 110. The multiplexed optical signal sent to the optical splitter 120 is input to variable wavelength selection elements 130 to 133, and is also input to the optical splitter 12.
The multiplexed optical signal sent to the variable wavelength selection element 133
~135. Variable wavelength selection elements 130 to 13
2 selects an optical signal of a predetermined wavelength for each time slot from the multiplexed optical signal input via the optical splitter 120 and outputs it to each of the optical bistable elements 700 to 702, and variable wavelength selection elements 133 to 135. selects an optical signal of a predetermined wavelength for each time slot from the multiplexed optical signal input via the optical splitter 121, and selects an optical signal of a predetermined wavelength from the multiplexed optical signal inputted via the optical splitter 121, and selects an optical signal of a predetermined wavelength from the multiplexed optical signal inputted via the optical splitter 121, and selects an optical signal of a predetermined wavelength for each time slot.
emit to. Optical bistable elements 700 to 702 each store an incident optical signal and fixedly convert its wavelength to λ1, and optical bistable elements 703 to 705 each store an incident optical signal and convert its wavelength. is also fixedly converted to λ2. readout optical switch 710,
711 is an optical bistable element 700 at a timing corresponding to each time slot on the output optical highway 170.
The optical signals stored in ~702, 703~705 are taken out to the output optical highway 170 via the optical combiner 170.

FIG. 8 shows optical bistable elements 700 to 705 in FIG.
FIG. 2 is a diagram for explaining one structure of FIG. In FIG. 8, the optical bistable element has one end surface 802 and the other end surface 803 of an active layer 801 shown by broken lines in an optical bistable semiconductor laser chip 800.
An incident light 804 is input to the second end face 802 , an outgoing light 805 is outputted from the same end face 802 , and another outgoing light 806 is outputted from the other end face 803 . Further, currents i2 and i3 are injected into the optical bistable semiconductor laser chip 800 through conductive wires 807 and 808, respectively. Therefore, the sum of currents i2 and i3 to the optical bistable semiconductor laser chip 800 is i2 +
i3 is injected as the injection current i.

FIGS. 9A, 9B, and 9C are diagrams for explaining the characteristics of the optical bistable elements 700 to 705 in FIG. 7. FIG. 9A is a diagram showing the relationship between the injection current i and the output light amount Pout when the incident light amount Pin=0. That is, when the injection current i is increased from 0, i=
When the output light amount Pout increases rapidly at it, and conversely, when the injection current i is decreased from i>it, the output light amount Pout increases rapidly.
out shows a hysteresis loop that rapidly decreases at i=ic, and the output light amount Pou decreases at i=ib.
Set state B where t = P1 and output light amount Pout
There are two stable points in the reset state A where =0. FIG. 9(b) is a diagram showing the relationship between the amount of incident light Pin and the amount of emitted light Pout when the injection current i=ib in FIG. 9(a). In other words, if the input light amount Pin is increased from 0 while in the reset state A where the output light amount Pout = 0, the output light amount Pout will rapidly increase when Pin = Ptb, and if the incident light amount Pout is subsequently decreased from the incident light amount Pin = Ptb to 0. In this case, the output light amount Pout hardly decreases and the state shifts to the set state B where the output light amount Pout = P1. Figure 9
Reset state A and set state B in FIG. 9(b) represent the same points as reset state A and set state B in FIG. 9(a), respectively. In this way, the optical bistable elements 910 to 915, which were initially in the reset state A at i=ib, have a Po
It is possible to change to the set state where ut = P1 and then maintain the set state B even if the incident light disappears. FIG. 9(c) shows the injection current i=i0 in FIG. 9(a).
Incident light amount Pin and output light amount Pout when <ic
FIG. In this case, the amount of incident light Pin=
0, the output light amount Pout = 0, and the incident light amount Pin
When increasing from 0, Pin = Pt0, the output light amount Pout increases rapidly and becomes Pout = P1,
Thereafter, when the amount of incident light is decreased to Pin=Pd0, the amount of output light becomes Pout=0. Therefore, the injection current i=ib
If the incident light amount Pin=0, the optical bistable elements 700 to 705 in the set state B with the output light amount Pout = P1 are brought into the reset state with the output light amount Pout = 0 by reducing the injection current i to i0. Can be done. Therefore, in advance, an optical bistable element having a hysteresis loop in the injection current vs. output light amount characteristic is set to have an injection current i=i0.
When the injection current i=ib is set, the optical bistable element changes to the set state or remains in the reset state depending on the presence or absence of incident light. Either one can be stored. Furthermore, the wavelength of the light emitted from the optical bistable element can be determined by keeping the injection current i constant and changing the amount of current distributed to currents i2 and i3 in FIG.
By increasing 2/i, it can be shifted to the short wavelength side, and by decreasing it, it can be shifted to the long wavelength side, and the wavelength of the emitted light from the optical bistable element can be set to a predetermined wavelength. For more information about optical bistable devices, please refer to the document ``Electronics Letters'' (ELECTRONICSLET).
TERS) September 24, 1987, Volume 23, No. 20, 108
Please refer to the description on pages 8 to 1089.

FIG. 10 is a time chart for explaining the operation of FIG.
A case where the signal A in the first time slot T1 with the wavelength λ2 above is outputted to the third time slot T3 with the wavelength λ1 on the output optical highway 170 will be explained. The variable wavelength selection element 130 in FIG. 7 has wavelengths λ1 and λ2, respectively.
Input optical highway signals 1000 and 1010 are input via branchers 110 and 120, respectively. Optical bistable element 700
The amount of current injection is periodically decreased and reset at the timing indicated by the injection current 1020. Then, the variable wavelength selection element 130 selects the wavelength λ2 in the first time slot T1.
Since the optical signal A is selected, the optical bistable element 700 can store either one of two values, changing to the set state or remaining in the reset state, depending on the presence or absence of the input optical signal 1030. Therefore, the optical bistable element 700
An output optical signal 1040 is emitted from. Here, the optical bistable element 700 has a wavelength λ of the input optical signal A.
2 is fixedly converted to λ1 and emitted. Therefore, when the readout optical switch 710 reads out the output optical signal 1040 of the optical bistable element 700 at the timing of the third time slot T3, as shown in the output optical highway 170 signal 1050 of the wavelength λ1, the input optical highway 100 has the wavelength λ2 The optical signal A in the first time slot can be switched to the wavelength λ1 of the output optical highway 170 in the third time slot T3 and output.

FIG. 11 is a diagram showing a specific example of readout optical switches 710 and 711 shown in FIG. 7. According to FIG. 11, input terminals 1, 2, and 3 are each connected to the optical bistable element 70 of FIG.
0,701,702 or 703,704,705. In addition, the output terminal 4 is connected to the optical combiner 160 in FIG.
connected to. Optical gate switch 1300, 1301,
1302 each input terminal 1 when a control signal is applied.
, 2 and 3 are outputted to the optical combiner 1310.

As explained above, the conventional wavelength division/time division optical switch shown in FIG. 7 moves an input optical signal of any wavelength and any time slot to a given wavelength and a given time slot. becomes possible.

[0009]

[Problem to be solved by the invention] Such wavelength division/
In a time-division composite optical switch, the optical signal stored in the optical bistable element continues to be emitted from the optical bistable element until a reset signal is applied to the optical bistable element. In order to read out the optical signal stored in the optical signal to the output optical highway, it is necessary to prepare a readout optical switch at the output of the optical bistable element and connect the output of the optical bistable element to the output optical highway only in a predetermined time slot. be. Therefore, when the wavelength multiplicity is n and the time division multiplicity is m, the variable wavelength selection element is used as an active optical component.
n pieces, m・n optical bistable elements, and m・n optical gate switches that constitute the readout optical switch, a total of 3
Since the number of active optical components is m.n, the number of required active optical components increases, resulting in an increase in the scale of the device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wavelength-division/time-division composite optical switch that does not require a readout optical switch and therefore requires fewer active optical components.

[0011]

[Means for Solving the Problems] The wavelength division/time division composite optical switch provided by the present invention has a plurality of variable wavelength division multiplexed optical signals for selecting a desired wavelength optical signal from input optical highway signals that have been wavelength division multiplexed and time division multiplexed. a wavelength selection element; and a first control signal connected to the output end of each of the plurality of variable wavelength selection elements to store an optical signal of a desired time slot of the output optical signal from the variable wavelength selection element; It is characterized in that it includes at least a plurality of optical memory elements that convert the optical signal stored in a desired time slot into a specific wavelength according to a control signal and output it to an output optical highway. Furthermore, the wavelength division/time division composite optical switch provided by the present invention includes a plurality of wavelength selection elements that select an optical signal of a predetermined wavelength from an input optical highway signal that has been wavelength division multiplexed and time division multiplexed; is connected to the output end of each of the wavelength selection elements of the wavelength selection element, and a first control signal stores the optical signal in a desired time slot of the output optical signal from the wavelength selection element, and a second control signal stores the optical signal in a desired time slot. It is characterized in that it includes at least a plurality of output wavelength tunable optical memory elements that convert the optical signal into a desired wavelength and output it to an output optical highway.

0012

[Operation] According to the wavelength-division/time-division multiplexed optical switch of the present invention, a predetermined wavelength is selected from input wavelength-division multiplexed and time-division multiplexed optical signals, and light of the selected wavelength in any time slot is After the signal is moved to a predetermined time slot, it can be converted into an optical signal of a different wavelength and output, so an optical signal of any wavelength and any time slot can be connected to any outgoing line, and the readout optical switch Therefore, in the case of wavelength multiplicity n and time division multiplicity m, the required active optical components are m/n variable wavelength selection elements, m/n optical memory elements, or m/n wavelength selection elements. In either case, the output wavelength tunable optical memory elements are m.times.n, for a total of 2.m.times.n, and the number of active optical components can be reduced compared to the conventional method.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a wavelength division/time division composite optical switch according to a first embodiment of the present invention. Wavelength division multiplicity 2,
An example of time division multiplicity 3 is shown.

The wavelength-divided and time-division multiplexed optical signals on the input optical highway 100 are sent to optical splitters 120 and 121 via an optical splitter 110. Optical splitter 120
The multiplexed optical signal sent to the variable wavelength selection elements 130 to 1
The multiplexed optical signal input to 32 and sent to optical splitter 121 is input to variable wavelength selection elements 133 to 135. The variable wavelength selection elements 130 to 133 are the optical branching device 120
selects an optical signal of a predetermined wavelength from the multiplexed optical signal inputted via and outputs it to each of the optical memory elements 140 to 142;
Further, the variable wavelength selection elements 133 to 135 are connected to the optical branching device 121.
Optical signals of desired wavelengths are selected from the multiplexed optical signals inputted via the multiplexed optical signals and outputted to optical memory elements 143 to 145, respectively.

The optical memory elements 140 to 142 are applied with a control signal at an arbitrary time slot timing from an incident optical signal, and thereby store the optical signal of a time slot corresponding to the timing at which the control signal is applied. . Further, the optical memory elements 143 to 145 receive the optical signal of the time slot according to the timing of applying the control signal by applying a positive voltage as a control signal at the timing of an arbitrary time slot from the input optical signal. remember. Then, the optical memory elements 140 to 140
By applying a positive voltage again to the optical memory elements 142, 143-145, the optical memory elements 140-142, 143-14
5 fixedly converts the stored optical signals into optical signals of wavelengths λ1 and λ2, respectively, and connects them to optical combiners 150, 160, and 1.
51 and 160 to output light highway 170.

FIG. 2 shows optical memory elements 140 to 145 in FIG.
FIG. 2 is a diagram for explaining one structure of FIG. In FIG. 2, the optical memory device has one end surface 220 and the other end surface 230 of a light guide layer 210, and one end surface 220 of the light guide layer 210.
The incident light 200 is input to 20, and the other end surface 23
Output light 250 is output from 0. Furthermore, a control signal V is applied via an electrode 240.

FIG. 3 shows optical memory elements 140 to 145 in FIG.
FIG. FIG. 3(a) is a diagram showing the relationship between the control voltage V and the current I flowing through the optical memory element. In the figure, when the incident light amount Pin=0, the control voltage V
When increasing from 0, the current I suddenly increases at V=Vs.
The thyristor exhibits an increasing characteristic, and has two stable points A1 and B1 on the load line l1 under one operating condition, or two stable points A2 and B2 on the load line l2 under another operating condition. FIG. 3(b) is a diagram showing the relationship between the current flowing through the optical memory element and the amount of light emitted from the optical memory element Pout. That is, the optical memory element has a threshold characteristic in which the current starts to flow from I=0 and when I exceeds It, the amount of output light Pout increases rapidly. Further, when Pin≠0, the optical memory element transitions from point A2 to point B2 on the load line l2 at a control voltage V2 smaller than Vs, and the optical memory element receives a current I.
2 flows. When the optical memory element transits to point B2, an optical signal with an incident light amount Pin is written into the optical memory element, and at the same time, an optical signal with an output light amount P2 is output from the optical memory element. Once the control voltage V is changed from V2 to 0V after an optical signal is written to the optical memory element, the current value I flowing through the optical memory element also becomes 0, and nothing is output from the optical memory element, but the voltage applied when the optical signal is written is Since the carrier of the optical signal with the control voltage V2 and the incident light amount Pin remains in the optical memory element, the optical signal is stored in the optical memory element even if the control voltage V is 0 and the incident light amount Pin of the optical signal is set to 0.

In order to read out the optical signal stored in the optical memory element, a control voltage V2 is applied to move the optical memory element to B.
When the transition is made to point 2, the current I2 flows through the optical memory element, so that the stored optical signal can be read out as an output optical signal with an output light amount P2. At this time, the wavelength of the optical signal emitted from the optical memory element is controlled by the peak value of the control signal Vb2 during readout, or by adjusting the value of the resistor connected to the electrode 240 in FIG. 2, the current value flowing to the optical memory element is controlled. The wavelength can be set to a desired wavelength. Furthermore, the wavelength of the output optical signal can be set to a desired wavelength by subjecting the optical memory element to temperature control.

[0019] Furthermore, the optical signal stored in the optical memory element is erased by applying a negative control voltage to the optical memory element and forcibly extracting all carriers remaining in the optical memory element out of the element. . Furthermore, when Pin=0, even if the control voltage V2 is applied, the optical memory element remains at B2.
Since there is no transition to the point, the optical signal is not stored, and therefore, even if the control voltage V2 is applied again, nothing is output from the optical memory element. Furthermore, in order to eliminate the influence of the light intensity of the output optical signal from the optical memory element when writing the optical signal to the optical memory element, the current that flows when the optical memory element transitions from point A1 to point B1 on the load straight line l1 is as shown in FIG. (b
), the threshold current It is less than or equal to I1 as shown in FIG. 3(a).
The control voltage V1 shown in FIG. 1 may be applied to the optical memory element. In other words, as shown in FIG. 6(b), the amount of light emitted from the optical memory element can be attenuated to the amount of light P1 corresponding to the current I1, which is extremely small compared to the amount of light P2 when reading out the optical signal. It is possible to suppress the influence of the amount of light emitted from the optical memory element when writing an optical signal to the element.

As explained above, the optical memory element is reset in advance by applying a negative control signal to the optical memory element, and then a positive control signal Vb1 is applied at the timing of an arbitrary optical signal time slot. to write an optical signal into the optical memory element. Next, by applying the positive control signal Vb2 at the timing of a predetermined time slot, the optical memory element can output the stored optical signal at the predetermined time slot. In addition, if the time slot of the optical signal input to the optical memory element is not moved, it is reset in advance with a negative control signal, and the control signal Vb2 is applied to the optical memory element at the timing of the time slot of an arbitrary optical signal. By doing so, the optical memory element outputs the input optical signal without moving the time slot. For details about optical memory devices, see K. Ka
sahara et al. , “Double het
erostructure opto electro
nic with a dynamic me
mory with low-power consu
mption”, Appl.phys.Lett. 5
2(a), 29 February 1988 or I. Ogura et al. , “A nove
l optical self-routing sw
itch with a wave length fi
altering function a v
vertical to surface transm
ission electro-photonic d
evice”, the 22nd Conference
ce on solid state devices
and materials, Sendai, pp.
533-536, 1990.

FIG. 4 is a time chart diagram for explaining the operation of FIG. The case of outputting to three time slots will be explained. The variable wavelength selection element 130 in FIG.
Input via 0. The optical memory element 140 has a control voltage 42
A negative voltage -VR is periodically applied and reset at the timing indicated by 0. and variable wavelength selection element 130
selects the optical signal of wavelength λ2 from the optical signals of wavelengths λ1 and λ2, so the optical memory element 140
0 in the first time slot T1 is stored and outputted in the third time slot T3. Here, the optical memory element 140 converts the wavelength λ2 of the input optical signal A into λ
Assuming that the wavelength λ1 is fixedly converted to λ1 and emitted, as shown in the output optical signal 440 of the optical memory device 140, the optical signal A having the wavelength λ1 is outputted from the optical memory device 140 in the third time slot T3. Therefore, the output optical signal 440 from the optical memory element 140 is outputted to the output optical highway 170 via the optical combiners 150 and 160, so that the first wavelength λ2 of the input optical highway 100 is output as shown in the output optical highway 170 signal 450.
The optical signal A of the time slot is outputted to the output optical highway 170.
can be switched to the third time slot T3 of the wavelength λ1 and output.

As explained above, by using the first embodiment of the present invention shown in FIG. It becomes possible to move it. In this case, when an optical signal is stored in the optical memory, a control signal is applied to the optical memory element at a predetermined time slot timing to convert the stored optical signal into an optical signal of a predetermined wavelength. Since it can be converted and taken out, there is no need for a readout optical switch that was required when conventional optical bistable devices were used as memory, and when the wavelength multiplicity is n and the time division multiplicity is m. The active optical components include m*n variable wavelength selection elements and m*n optical memory elements, so the number of active optical components can be reduced to 2m*n in total.

FIG. 5 shows wavelength division/wavelength division according to the second embodiment of the present invention.
1 is a diagram showing a time division composite optical switch; FIG. Again, an example of a wavelength division multiplexing degree of 2 and a time division multiplexing degree of 3 is shown.

The wavelength-divided and time-division multiplexed optical signals on the input optical highway 100 are sent to optical splitters 120 and 121 via an optical splitter 110. Optical splitter 120
The multiplexed optical signal sent to the wavelength selection elements 500 to 502
The multiplexed optical signal input to the wavelength selector 121 and sent to the optical splitter 121 is input to the wavelength selection elements 503 to 505. The wavelength selection elements 500 to 502 select an optical signal of wavelength λ1 from the multiplexed optical signal input via the optical splitter 120, and output it to the output wavelength variable optical memory elements 510 to 512, respectively.
Further, the wavelength selection elements 503 to 505 select an optical signal of wavelength λ2 from the multiplexed optical signal input via the optical splitter 121, and output it to the output wavelength variable optical memory elements 513 to 515, respectively.

Output wavelength tunable optical memory elements 510 to 512
By applying a control signal at the timing of an arbitrary time slot from an incident optical signal, the optical signal of the time slot corresponding to the timing of application of the control signal is stored. In addition, the output wavelength variable optical memory element 513
515 stores an optical signal of a time slot corresponding to the timing of application of the control signal by applying a control signal at the timing of an arbitrary time slot from the input optical signal. Then, by applying a control signal again to the output wavelength tunable optical memory elements 510 to 515 at a timing corresponding to each time slot on the output optical highway 170, the output wavelength tunable optical memory elements 510 to 512
Alternatively, each of 513 to 515 converts the wavelength of the stored optical signal to either λ1 or λ2 and outputs it to the output optical highway 170 via the optical combiner 150, 160 or 151, 160.

FIG. 6 is a time chart for explaining the operation of FIG. 5. As an example, the input optical highway 1
Signal A of the first time slot T1 of wavelength λ2 on 00
The case where the signal is outputted to the third time slot of wavelength λ1 on the output optical highway 170 will be explained. The wavelength selection element 503 in FIG.
Enter via 21. Output wavelength variable optical memory element 513
is a negative voltage -VR at the timing shown in the control voltage 620
is applied periodically and reset. Then, the wavelength selection element 503 selects the wavelength λ2 from the optical signals of the wavelengths λ1 and λ2.
, the output wavelength tunable optical memory device 513 selects the first time slot T1 of the input optical signal 630.
The optical signal A is stored and is emitted at the third time slot T3. Here, assuming that the optical memory element 140 converts the wavelength of the input optical signal A to λ1 of λ1 and λ2 and emits it, the output wavelength variable optical memory element 5
As shown in the output optical signal 640 of No. 13, the wavelength λ1
The optical signal A is outputted from the output wavelength tunable optical memory device 513 in the third time slot T3. Therefore, the output optical signal 640 from the output wavelength tunable optical memory element 513 is outputted to the output optical highway 170 via the optical combiners 151 and 160, so that the wavelength λ2 of the input optical highway 100 is The optical signal A in the first time slot can be exchanged and outputted to the third time slot T3 of the wavelength λ1 of the output optical highway 170.

As explained above, the second embodiment of the present invention shown in FIG.
By using this embodiment, it is also possible to move an input optical signal of any wavelength and any time slot to a predetermined time slot of a predetermined wavelength. Also in this case, when the optical signal is stored in the output wavelength tunable optical memory, the stored optical signal can be arbitrarily changed by applying a control signal to the output wavelength tunable optical memory element at the timing of a predetermined time slot. Since it is possible to convert the optical signal into an optical signal with a wavelength of In this case, the necessary active optical component is a wavelength selective element.
・n pieces, m·n output wavelength tunable optical memory elements,
Therefore, the number of active optical components can be reduced to 2m·n in total.

[0028]

[Effects of the Invention] As described above, the wavelength division and
According to a time-division composite optical switch, an optical signal of any wavelength and any time slot can be connected to any outgoing line, and a readout optical switch is not required, so the number of active optical components can be reduced compared to conventional systems.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram for explaining one structure of the optical memory element in FIG. 1;

FIG. 3 is a diagram for explaining the characteristics of the optical memory element in FIG. 1;

FIG. 4 is a time chart diagram for explaining the operation of FIG. 1;

FIG. 5 is a diagram showing a second embodiment of the present invention.

FIG. 6 is a time chart diagram for explaining the operation of FIG. 5;

FIG. 7 is a diagram showing a conventional wavelength division/time division composite optical switch.

8 is a diagram for explaining one structure of the optical bistable element in FIG. 7. FIG.

9 is a diagram for explaining the characteristics of the optical bistable element shown in FIG. 7. FIG.

FIG. 10 is a time chart diagram for explaining the operation of FIG. 7;

FIG. 11 is a diagram showing a specific example of the readout optical switch shown in FIG. 7;

[Explanation of symbols]

Claims (2)

[Claims] 1. A plurality of variable wavelength selection elements for selecting an optical signal of a desired wavelength from wavelength division multiplexed and time division multiplexed input optical highway signals, and a plurality of variable wavelength selection elements connected to an output end of each of the plurality of variable wavelength selection elements. A first control signal stores the optical signal in a desired time slot of the output optical signal from the variable wavelength selection element, and a second control signal converts the optical signal stored in the desired time slot into a specific wavelength. and a plurality of optical memory elements for outputting to an output optical highway.
Time division composite optical switch. 2. A plurality of wavelength selection elements for selecting an optical signal of a predetermined wavelength from an input optical highway signal that has been wavelength division multiplexed and time division multiplexed, and connected to an output end of each of the plurality of wavelength selection elements. A first control signal stores the optical signal in a desired time slot of the output optical signal from the wavelength selection element, and a second control signal converts the optical signal stored in the desired time slot into a desired wavelength. What is claimed is: 1. A wavelength-division/time-division composite optical switch, comprising at least a plurality of output wavelength-tunable optical memory elements that emit the output to an output optical highway.