JPH0586714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical time switch that exchanges time slots by converting the phase of an optical signal as it is without converting the time slot of an optical signal into an electrical signal.

(Prior Art) FIG. 3a is a diagram showing a conventional optical time switch constructed by cascading a loop-shaped optical delay line and an optical switch. FIG. 3b is a diagram showing a timing chart of time slot exchange in this optical time switch.

In FIG. 3a, 1 is the incoming line of the n-multiplexed time-division optical transmission line, 101, 102, 103 is the 2×2 optical time switch, 7 is the outgoing line of the n-multiplexed time-division optical transmission line, 104, 105 , 106 are T/n, respectively.
This is an optical delay line that delays T and T/n times.
It should be noted that the diagrams .

The operating principle of a conventional optical time switch will be explained with reference to FIG. To make the explanation easier to understand, let us assume that the time slot consists of 1 bit and the time slot time is T, as shown in Figure 3b, and we will explain the case where time slots A and B are exchanged. . When n time slots are input to the input line 1, the time slot A at the optical head first passes through the optical switch 101 in the through state without delay and is input to the optical switch 102.
2, the T is made into a cross state and passed through the optical delay line 105
After receiving a time delay, the signal is input to the optical switch 103, and in the optical switch 103, it is first put into a cross state every T/n cycle, then put into a through state (n-1) times, and finally put into a cross state, resulting in an optical delay. Through the line 106, the output line 7 is delayed by T (=T/n×1+T/n×(n-1)), resulting in a delay of 2T.
is output to. Similarly, for the next time slot B, by controlling each optical switch, the optical switch 101 performs T/n time, and the optical switch 102 performs (n-
1) T time, (n-1)T/ with optical switch 103
It is delayed by n hours and is output to the outgoing line 7 with a delay of nT as a result. Based on the input time slot A time, the output A is -2T
At the position of
Since it is delayed by -nT-T (this can be considered as -T since nT is the frame period), output A is delayed by T from output B. This means that A and B have been exchanged. The above-mentioned exchanging operation of A and B is actually carried out under the control of the optical switch 102, but in order to prevent the time slots from overlapping each other during this exchanging operation, it is necessary to At the optical switch 101, A is 0, B is T/n, C
is delayed by 2T/n,..., and finally A is delayed by T (=T
-0), B is (n-1)T/n (=T-T/n),
C is delayed by (n-2)T/n (=T-2T/n), and is returned to the original phase delayed by T as a whole. In addition, when the time slot is composed of m bits, the optical delay lines 104, 105, 1
The delay times of 06 are T/mn, T, T/mn, respectively.
And it is sufficient.

(Problems to be Solved by the Invention) As described above, in the conventional optical time switch, T/
An optical switch capable of switching every n cycles is required, and the switching speed increases as the degree of multiplicity increases.

An object of the present invention is to provide an optical time switch that does not require increasing the speed of the optical switch even if the multiplicity of the optical transmission line is increased.

(Means for Solving the Problems) The present invention provides the following steps in order to prevent the time slots from overlapping each other during the exchange operation when an optical signal of wavelength λ ₀ consisting of n time slots is input. Each of the n time slots is set to a different λ ₁ ~
After converting the wavelength to _λo , a delay is added using an optical delay line, and by controlling the optical switch of the input/output section provided for each wavelength, the delay required for time slot exchange is applied to each wavelength. Make it.

(Function) With the above configuration, there is no need to increase the speed of the optical switch even if the number of time slots is increased, and an optical time switch that achieves the above object can be obtained.

(Embodiment) 1 is an input optical transmission line with a multiplicity of n, and 2 is a first system that sequentially converts the wavelength λ ₀ of an optical signal on the input optical transmission line into n different wavelengths λ ₁ to λ _o for each time slot. This is a wavelength conversion circuit. Reference numeral 3 denotes a first optical demultiplexer, which demultiplexes each wavelength λ ₁ to λ _o , and its output is sent to the input terminal of each of the 2×2 path switching optical switches 41 to 4n provided for each wavelength. connected to one side of the The 2.times.2 path switching type optical switches 41 to 4n perform switching between the parallel state and the cross state as shown in FIG. 1b. Reference numeral 5 designates a first optical multiplexer, which is connected to one of the output terminals of each of the 2×2 route switching type optical switches 41 to 4n, and is connected to one of the output terminals of each of the 2×2 route switching type optical switches 41 to 4n.
The wavelengths λ 1 to λ o outputted from the wavelengths λ ₁ to λ _o are multiplexed. Reference numeral 6 denotes a second wavelength conversion circuit that converts the wavelengths λ ₁ to λ _o outputted from 5 back to the wavelength λ ₀ of the output optical transmission line 7 . 8 is the second
It is an optical multiplexer connected to the other one of the output terminals of each of the 2x2-way switching type optical switches 41 to 4n, and is connected to the other one of the output terminals of each of the 2x2-way switching type optical switches 41 to 4n, and has wavelengths λ ₁ - Combine λ _o . Reference numeral 9 denotes a delay line that provides a delay time of the time slot interval T for all wavelengths from λ ₁ to λ _o . Reference numeral 10 denotes a second optical multiplexer, which demultiplexes each wavelength λ ₁ to λ _o , and its output is connected to the other input terminal of each of the 2×2 path switching optical switches 41 to 4n. Ru. Reference numeral 11 denotes a control unit, which controls the first wavelength conversion circuit 2 to convert the wavelength λ ₀ of the optical signal on the input optical transmission line into n different wavelengths λ ₁ to λ _o sequentially for each time slot. The 2×2 path switching type optical switches 41 to 4n are controlled to switch between the parallel state and the cross state according to the switching control information. Regarding the control of the second wavelength conversion circuit 6, the wavelengths λ ₁ to _{λ o} are output through the optical transmission line 7.
Control is performed to convert the wavelength λ 0 to the wavelength λ ₀ .

In order to perform time slot exchange, the i-th
The case where the th time slot is delayed by the time jT and converted into the i+jth time slot will be explained. First, the optical signal of wavelength λ ₀ in the i-th time slot is converted to λ _i in the first wavelength conversion circuit. and λ _i of the first optical demultiplexer 3
output to the output terminal. If the 2×2 optical switch 4i provided for the wavelength _λi is controlled to be in a crossed state, the optical signal of _λi will pass through the second optical multiplexer 8 to the optical delay line 9. I am guided. λ _i
When the signal passes through the 2×2 optical switch 4i and is input to the optical delay line, the switch is switched from the cross state to the parallel state. The switches are then held in the parallel state until the optical signal passes through the optical delay line a total of j times. That is, the optical signal is transmitted through the optical delay line 9, the second optical demultiplexer 10, and the 2×2
It continues to circulate through the loop constituted by the route switching optical switch 4i and the second optical multiplexer 8. Total j
After the cycle, the switch is again switched to the cross state, and the signal of λ _i outputted from the 2×2 path switching type optical switch 4i is guided to the second wavelength conversion circuit through the first optical multiplexer 5, and the wavelength After being converted into λ ₀ , it is output to the output optical transmission line 7.

When the above operation is being performed, the time slot conversion operation is also performed simultaneously for the signals in time slots other than the i-th time slot, but in that case, the wavelength in the loop is always other than λ _i , so the signals are different from each other. No polymerization occurs.

It is well known that the delay amount of the optical delay line 9 differs depending on the wavelength, but since the difference is extremely small, the influence of the wavelength can be ignored in the high speed range where the delay time is short.

Next, a description will be given using a specific example of operation.

FIG. 2 is a diagram showing the timing chart and operating wavelength of the present invention, and the multiplicity of the input optical transmission line is 3.
This is an example in which each channel is composed of 1 bit. Symbols a to g in the figure correspond to those in FIG. The operation when exchanging channels A and C will be described below with reference to FIGS. 1 and 2.

The wavelength conversion circuit 2 converts the wavelength of channel A to λ ₁ , channel B to λ ₂ , and channel C to λ ₃ . The optical signals of channels A, B, and C are demultiplexed by three optical demultiplexers and sent to optical switches 41, 42, and 4, respectively.
3 is input. The optical switch is controlled so that it is in a cross state when inputting and outputting optical signals to and from the optical delay line, and in a parallel state at other times. In this example, in order to delay the optical signal of channel A by two time slots, the optical switch 41 is first put into a cross state and inputted to the optical delay line 9 via the multiplexer 8, and then the optical switch 41 is put into a parallel state and the optical signal is input into the optical delay line 9. After the signal has made two rounds through the optical delay line 9, it is put into a cross state again and output to the multiplexer 5. Since the optical signal of channel B is not delayed, the optical switch 42 puts it in a parallel state from the beginning and outputs it to the multiplexer 5. The optical signal of channel C is delayed by one time slot, so the optical switch 43 is set to the cross state, and the optical signal is inputted to the optical delay line 9 through the multiplexer 8.
After going around once, the signal is output to the multiplexer 5. After the optical signals of each channel are multiplexed by a multiplexer 5, the wavelength is converted to λ ₀ by a wavelength conversion circuit 6, and the signal is output to an output optical transmission line.

As is clear from the above explanation, since the optical signals of each channel are converted into wavelengths different from each other, time slots can be exchanged without any collision of optical signals.

(Effects of the Invention) The present invention is configured as if a set of optical delay line and optical switch were installed for each time slot, so the speed of the optical switch is not affected by the number of time slots, and high multiplexing is possible. An optical time switch that can be applied to optical transmission lines can be easily constructed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention, FIG. 2 is a diagram showing the timing chart and operating wavelength of the present invention, and FIG. 3 is a diagram showing the configuration and timing chart of a conventional optical time switch. DESCRIPTION OF SYMBOLS 1... Input optical transmission line, 2... First wavelength conversion circuit, 3... First optical demultiplexer, 41, 42 to 4n...
2×2 path switching optical switch, 5... first optical multiplexer, 6... second wavelength conversion circuit, 7... output optical transmission line, 8... second optical multiplexer, 9... ... Optical delay line, 10 ... Second optical demultiplexer, 11 ... Control unit,
λ ₀ , λ ₁ ~ λ _o ...wavelength.

Claims (1)

[Claims] 1. An input terminal connected to a time division multiplexed optical transmission line,
a first wavelength conversion circuit that converts wavelengths to different wavelengths for each time slot; a first optical demultiplexer that has an input terminal connected to the output terminal of the first wavelength conversion circuit and demultiplexes each wavelength; A 2x2 path switching type optical switch is provided for each wavelength, with one input terminal connected to each output terminal of the optical demultiplexer, and an input terminal connected to one of the output terminals of each optical switch. the first connected
an input/output section consisting of an optical multiplexer, and a second wavelength conversion circuit whose input terminal is connected to the output terminal of the first optical multiplexer and whose output terminal is connected to the output optical transmission line; and an input/output section of each optical switch. A second optical multiplexer whose input terminal is connected to the other side of the output terminal, and an input terminal connected to the output terminal of the second optical multiplexer, and the delay amount of the time slot interval for all wavelengths of the optical signal. a second optical demultiplexer whose input terminal is connected to the output terminal of the optical delay line and whose output terminal is connected to the other input terminal of the optical switch for each wavelength. The input and output of each optical switch is connected so that the delay time necessary for exchanging the time slot of the wavelength corresponding to the optical switch is obtained by the optical delay line. The light output from the optical switch after time slot exchange is combined by the first optical multiplexer, and each wavelength of the output is converted to its original wavelength by the second wavelength conversion circuit. An optical switch characterized by reconversion and output.