JPS6156594A - Optical time switch - Google Patents

Abstract

PURPOSE:To permit the exchange of optical signals with fewer number of photo delay elements than time division multiplex by connecting a photo delay circuit consisting of delay elements which use one time slot as a delay time unit and that consisting of delay elements which use n number of time slots as a deley time unit using a photo switch. CONSTITUTION:A delay circuit 8 conncects n pieces of delay elements in series which delay an input photo signal for t (one time slot time), and installs a photo switch in input or output side of each delay element. The time-dividing multiplexed (N-plexed) photo signal of each time slot which is input to the delay circuit 8 from an input highway 4 passes through thenecessary number of stages in the delay elements 11, is output by a photo switch 3i, and is input to the delay circuit 9 via n x m photo switch 2. The delay circuit 9 connects m pieces of delay elements 21 in series which delay input photo signal for n times t, and installs a photo coupler in input or output side of each delay element. The photo signal input from the photo coupler 4 passes through the delay element 21 for j stages, and is output from an output highway 5; provided that (m-1)n<N<=mn.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an optical time switch, and particularly to a time switch such as an optical time division switch that exchanges time division multiplexed light (No. 3) as it is. I can do it.

[Background of the invention]

This kind of conventional! In the A position, there are those that use an optical delay element and those that use an optical memory using an optical bistable element.
In order to exchange multiple optical signals, N optical delay elements are required in the former case, and NQ optical memories (2 is the number of bits in one time slot) are required in the latter case.
There is a drawback that as the time division multiplexing degree N increases, the amount of hardware for delay circuits and memory circuits increases.

[Purpose of the invention]

The purpose of the present invention is to improve upon such conventional drawbacks, and to make it possible to replace optical delay elements (No. The object of the present invention is to provide an advantageous optical time switch.

[Summary of the invention]

In order to achieve the above object, the optical time switch of the present invention includes:
In an optical time switch that switches time slots on a highway that transmits N time-division multiplexed optical signals,
It has n types of delays (0, 0,
t, 2 t, 3 t,...

(n I) t, where ≦N, t = (I time thrower 1- time)) is set to 'j', and then the delay (outputs the r1 light to one output terminal a first optical delay circuit ( ), an input optical signal having an input ψ11 circuit and an input terminal corresponding to an input optical signal;
Ji Nobu (0, n.

t, 2n t, 3n t, ==, (m-1)n t, where (m-1)n<N5m11), the second optical delay circuit outputs to one output highway. It is characterized in that the first and second optical delay circuits are connected by a non-blocking solo switch with n inputs and m outputs.

[Embodiments of the invention]

FIG. 1 shows the components of an optical time switch showing an embodiment of the present invention, in which 1 is an IXn optical switch (Sochi), 2 is an nXm optical switch, 3 is an mX1 optical coupler, 4 is an input highway, and 5 is an optical time switch.
is the output highway, 6 is the first delay circuit, 7 is the second delay circuit, 10, 11, 12°-, 1(n-1) is the first delay element group, 20, 21° 22,... ..., 2(
m-1) is the second delay strand group.

The first optical time switch includes a delay circuit whose delay unit is L (the time of l time slot) and a delay circuit whose delay unit is nt (an integral multiple of t) to give the delay to the optical No. 48. This is realized by a combination of two types of delay circuits, and this makes it possible to exchange m number of lights with a smaller number of delay elements than the number of time division multiplexers.

First, an overview of the operation will be explained. The time-division multiplexed (N-multiplexed) optical signals of each time slot 1- inputted from the input highway 4 are sent to the first delay element group 10-1 by the optical switch 1.
1(n-1) to an appropriate delay element. 1st
The delay element groups 10 to 1 (n-1) have the time t of one time slot as a unit of delay, and the delay elements 10 have a delay time of 0, 11 have a delay time t, and 12 have a delay time of 2 t.
, +・++, 1 (n - 1) is the delay time (n - 1)
t, and the optical switch l selects a delay element corresponding to the required delay time for each slot time from among them. The signal is again input to an appropriate delay element in the delay element groups 20 to 2 (m-1). The second delay element group 20 to 2 (m-1) has a delay unit of nt,
The delay element 20 has a delay time of 0.21 and a delay time of nt, 22
is the delay time 2nt, . . . , 2(m-1) is the delay time (ml) nt. The light (i) which has been delayed by the second delay cable group is output onto the output highway 5 of one upstream mXlXl optical coupler.

Next, a method for selecting the first and second delay elements will be explained. Considering the case where an optical signal in a certain time slot on input highway r4 is given a delay of X (X is a natural number smaller than the multiplicity N), X is x = i + j n
Therefore, instead of giving a delay of xt, iXt and j
The delays of Xnt may be applied separately and consecutively. Here, for x and n which are 0≦X≦N-1 1≦n≦N, 0≦1≦n-1+o≦j'
Since I+J is uniquely determined, use i and j to select the strings 11 and 2j from the first and second delay elements;
All you have to do is choose 4. is the maximum value of n and j (m-1)
is a natural number satisfying (rn −1)n <N≦mn.

Delay elements 10-1 (n-1) and 20-220-2 (
can be realized using an optical fiber with a length corresponding to the delay time.

When an N-multiplexed optical time switch is created with such a configuration, the number of delay elements becomes n+m, and when the multiplicity N is large, the number of delay elements can be effectively reduced.

FIG. 2 is a block diagram of an optical time switch showing another embodiment of the present invention, in which 8 is a first delay circuit, 9 is a second delay circuit, 30, 31, 32, ---=, 3(n-2)
, 3(n-1) is the optical switch of IX2, 40°...
, 4(m-2), and 4(m-1) are 2X1 optical couplers.

Other details are the same as in Figure 1. The operation will be explained below.

Since the difference from FIG. 1 is only in the configurations within the first and second delay circuits (6° 8 and 7, 9), only that portion will be explained. The delay circuit 8 is constructed by connecting delay elements 11 in series that give an earlier delay to the input optical signal 18, and providing an optical switch of IX2 on the input or output side of each delay element. The light (No. 3) is outputted by the optical switch 31 after passing through the delay element 11 for the required number of stages.

The delay circuit 9 has delay elements 21 which give a delay of nt to the input light (n) connected in series, and a 2Xl optical coupler is provided on the input or output side of each delay element, and the optical coupler 4j
After passing through the delay element 21 in j stages, the optical signal inputted from the output highway 5 outputs from the output highway 5.
The delay circuit 8 has a delay unit of t, and the delay circuit 9 has a delay unit of n[
Each can be given a delay in units of .

In the method shown in FIG. 2, it is possible to further reduce the number of claws in the delay element compared to the method shown in FIG.

In both Fig. 11g and Fig. 2, the rr of the first and second delay circuits is
It is clear that even if the number i is replaced, the same effect as described above can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, in order to configure N multiplexed optical time switches ti-, n and m are set as (m-1
)n<N≦mn by adding 1 to 1, the number of delay elements can be reduced by 1llll compared to N, and the advantage is that the reduction effect is particularly significant when N is large. There is.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of the invention, and FIG. 2 shows a second embodiment of the invention. 1: IXn optical switch, 2: nXm optical switch. 3: rnX optical coupler, 4: Input highway, 5:
Output highway, 6, 8: first delay circuit, 7, 9: second delay circuit, I O, 11, 12, -, 1 (n-1)
: first delay element group, 20, 21.22. −． 2(m-
1): second delay element group, 30, 31, 32. .... 3(n-2), 3(n-1): 1 x 2 optical switch. 40, -4(m-2), 4(m-1): 2X1 optical coupler.

Claims (1)

[Claims] In an optical time switch that switches time slots on a highway for transmitting time-division multiplexed optical signals, a first optical delay circuit in which delay elements each having one time slot as a delay time unit are connected in parallel or in series, and n time slots ( n
: a second optical delay circuit in which delay elements whose delay time unit is a number smaller than the number of time division multiplexed units are connected in parallel or in series, and an optical switch that connects the first and second optical delay circuits. An optical time switch characterized by having: