JP2690310B2 - Optical switching system - Google Patents

Description

The present invention relates to an optical switching system for setting a path for optical communication between arbitrary terminals in an optical communication network to which a large number of terminals are connected, and using an optical functional device in a practical stage, For the purpose of realizing an optical switching system, the optical signal from the input side optical highway is switched for each time slot, and the light of a number of different wavelengths corresponding to the number of the input side optical highway is selectively changed. The wavelength allocation phase conversion means allocated to the optical signal of the time slot and the optical signal allocated the wavelength by the wavelength allocation phase conversion means are separated for each wavelength for each input side optical highway, and are set for each wavelength. It comprises a wavelength gate means for outputting to the output side highway, and a phase converting means for switching an optical signal from the output side optical highway for each time slot. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switching system for setting a path for optical communication between arbitrary terminals in an optical communication network to which a large number of terminals are connected, and particularly without converting an optical signal into an electric signal. The present invention relates to an optical switching system for directly switching. In recent years, in order to cope with the increase in the line capacity and the increase in transmission speed in public lines, researches are being conducted in various places to extend the digital switching technology to optical communication networks and apply it. Especially, in the optical switching system that directly exchanges light without converting it into an electric signal, many effects can be expected as shown below.Therefore, optimization of various systems has been sought in order to realize it. ing. The effects of implementing the optical switching system are as follows. (B) The optical transmission line, including the switching equipment, will have high speed, wide bandwidth, and low loss. (B) Crosstalk is reduced irrespective of the signal speed due to the electromagnetic non-inductivity. (C) The response speed does not change depending on the fanout number. (D) Mounting does not require grounding of the signal part. By directly processing the optical signal in this way, the characteristics of the exchange are dramatically improved. 2. Description of the Related Art FIG. 7 is an explanatory diagram showing a typical example of a time division optical switching system. For example, a four-line time-division multiplexed optical signal transmitted through one input-side optical highway 61 is sequentially bit-by-bit by a 1 × 4 optical switch 62 into four bistable semiconductor lasers 63-.
It is incident on the optical memory 63 composed of 1, 2, 3, and 4. When the incident signal is "1", the relevant portion is set to the ON state in the optical memory 63, and this state is held until it is electrically reset. Then, these optical signal outputs are read out at a time corresponding to a channel to be connected via the 4 × 1 optical switch 64 connected to the output side optical highway 65, so that the signal of one channel is transferred to another channel. It can move on-axis and realizes time-division optical switching function. FIG. 8 is an explanatory diagram showing a method for exchanging a plurality of input side optical highways 71 and a plurality of output side optical highways 75 as the number of lines increases. Reference numerals 72 and 74 denote optical phase conversion switches configured by applying the time division optical switching system shown in FIG. 7, and correspond to time switches (T switches) in the electrical digital switching technology. 73 is an optical phase conversion switch that outputs the optical signal from the optical phase conversion switch 72 in a time division manner.
It is a time division optical gate switch for distributing to 74 and corresponds to the space switch (S switch) in the same technology. The multiplexed optical signal transmitted through each input side optical highway 71 has its multiplexing order, that is, time position, exchanged by the optical phase conversion switch 72, and a time division optical gate switch is provided.
The data is periodically distributed to the optical phase conversion switch 74 on the desired line by 73 by each bit. Then, the order of multiplexing is returned to the original state and the original multiplexed signal is restored. This system corresponds to the conventional T-S-T system in operation principle. As a method proposed in addition to the T-S-T method, there is a λ-Sλ-λ method shown in FIG. In this method, the wavelength of the optical signal that has been wavelength-multiplexed and transmitted through the plurality of optical transmission lines 81 is converted by the wavelength conversion switch 82 according to the switching path and is made incident on the wavelength division optical gate switch 83. ing. Wavelength division optical gate switch 83
Is for distributing the input optical signal for each wavelength according to the exchange path. The wavelength-multiplexed signal light distributed for each wavelength has its wavelength further converted by the wavelength conversion switch 84 and is output to the output side optical transmission line 85. Problems to be Solved by the Invention In the time division optical switching system shown in FIG. 7 among the above-mentioned conventional systems, the development of optical devices such as an optical memory and a high-speed optical switch is progressing, and it is practical. Although the system can be provided, there is a problem in that the number of exchange paths is limited when trying to achieve a certain exchange rate. This is because it is necessary to reduce the number of exchange paths in order to increase the exchange speed, and to improve the exchange speed in order to increase the number of exchange paths. In the system shown in FIGS. 8 and 9,
Although the operating principle itself has been proposed, the current situation is that the development of constituent optical devices has not progressed. For example, the time division optical gate switch 73 and the ninth
It is said that it is difficult to realize the wavelength conversion switches 82 and 84 shown in the figure with existing optical devices. The present invention was created in view of such circumstances, and it is possible to realize high-speed, high-speed operation by using an optical functional device in a practical stage.
The purpose is to realize a large-capacity optical switching system. Means for Solving Problems FIG. 1 is a principle configuration diagram of the present invention made to solve the problems of the above-described conventional technology. Reference numeral 2 denotes a wavelength allocation phase conversion means, which exchanges the optical signal from the input side optical highway 1 for each time slot, and selectively outputs light of different wavelengths corresponding to the number of input side optical highways. It is assigned to the optical signal of the time slot. Reference numeral 3 denotes a wavelength gate means for separating an optical signal having a wavelength assigned by the wavelength assignment phase conversion means 2 for each wavelength of each input side optical highway 1 and setting an output side optical highway for each wavelength. Output to 4. Reference numeral 5 is a phase conversion means, which exchanges the optical signal from the output side optical highway 4 for each time slot. The time-division multiplexed optical signal transmitted via the input-side optical highway 1 is switched by the wavelength allocation phase conversion means 2 for each time slot. At this time, the number of different wavelengths corresponding to the number of input side optical highways is assigned to the optical signal for each time slot, so that the wavelength gate means 3 allocates the wavelengths to the respective output side optical highways 4. You can The optical signal distributed for each wavelength is returned to the original order of multiplexing again by the phase conversion means 5. Therefore, as compared with the time-division multiplex optical conversion system that only performs the phase conversion, high speed and large capacity can be achieved. Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows a specific configuration example of the wavelength assignment phase conversion means. The optical signal time-division multiplexed at the time multiplicity m is passed through the input side optical highway 11 to the random switch 12
Are input to the optical waveguide 13-1, 2, ...
Each of the memory blocks of the optical memory 14 are allocated to
Input to 14-1, 2, ..., m. Each memory block, for example, the memory block 14-1 has λ ₁ , λ ₂ , ..., λ _n
It is composed of memory cells (bistable semiconductor lasers) that can maintain the light emission state at each wavelength, and one of the memory cells operates selectively by controlling the applied voltage pattern of each memory cell. It can be done. When the wavelength λ ₂ is allocated in the memory block 14-1, for example, the applied voltage of each memory cell is once set to a value equal to or lower than the operation threshold value and reset, and the memory cell corresponding to the wavelength λ ₂ is configured as a bistable semiconductor. An optical signal may be input through the optical waveguide 13-1 in a state where a voltage higher than the operation threshold is applied only to the laser. As a result, the optical waveguide 13 is made to emit light of the wavelength λ _2.
The bit signal from -1 can be temporarily stored in the memory block 14-1. By each memory block performing the above operation, the time-division multiplexed optical signal with time multiplicity m is temporarily stored in each memory block 14-1, 2, ..., M with spatial multiplicity m. . Therefore, these stored signal lights can be taken out by the sequential switch 16 in a predetermined order and sent to the input side optical highway 17. 15-1, 2, ..., M are optical waveguides that connect the optical memory 14 and the sequential switch 16, and the optical memory side thereof is branched and connected to each memory cell. The optical waveguides 13-1, 2, ..., M are similarly branched and connected to each memory cell. The number n of cells in each block corresponds to the number of optical highways. FIG. 3 shows a specific example of the structure of the wavelength gate means. , 21 are input-side optical highways, and their output terminals are connected to the demultiplexers 22-1, 2, ..., N, respectively. The optical signals of wavelengths λ ₁ , λ ₂ , ..., λ _n output from the respective demultiplexers are multiplexers (optical couplers) 23-1, 2,
…, N, and output side optical highway 24-1, 2,
..., sent to n. FIG. 4 shows a specific configuration example of the phase conversion means. The optical signal input through the output-side optical highway 31 is sequentially distributed bit by bit by the random switch 32 to the optical waveguides 33-1, 2, ..., M, and each memory cell 34-1 of the optical memory 34 is divided. , 2, ..., m are input. Each memory cell is composed of a bistable semiconductor laser and can hold its oscillation state by using an optical signal of wavelengths λ _{1 to} λ _n as a trigger. Therefore, the optical waveguides 35-1, 2,
, M, the stored optical signals are taken out by the sequential switch 36, so that the signal positions on the time axis can be exchanged and sent to the output side optical highway 37. FIG. 5 is a diagram for explaining the operation of the optical switch configured using the wavelength assignment phase conversion switch, the wavelength gate switch, and the phase conversion switch described above. Here, the number of optical highways is 2 and the number of time division multiplexing is 4 for convenience. Optical signals A, B, C, D transmitted via the subscriber line 41
Are multiplexed by the multiplexing circuit 42 on t ₀ , t ₁ , t ₂ and t ₃ on the time axis in the order of A, B, C and D, respectively. Then, the wavelength-assigned phase conversion switch 44 replaces the position on the time axis, and the number of different optical highways is equal to two.
Two wavelengths λ ₀ , λ ₁ are assigned, and D (λ ₀ ), C (λ
₁ ), A (λ ₀ ), B (λ ₀ ) in this order
Entered in 46. On the other hand, similarly for the other optical highways, the optical signals E, F, G, H multiplexed by the multiplexing circuit 43 are transmitted by the wavelength allocation phase conversion switch 45 to H (λ ₁ ), E.
(Λ ₀ ), G (λ ₁ ), F (λ ₁ ) are exchanged in this order, and respective wavelengths are assigned to the wavelength gate switch 46. In the wavelength gate switch 46, the wavelength λ
The optical signals D, E, A and B of ₀ are sent to the phase conversion switch 47 in this order, and the optical signals H, C, G and F of the wavelength λ ₁ are sent to the phase conversion switch 48 in this order. In the phase conversion switch 47, the input optical signal is E, D, A, B
The order of the subscriber line is changed by the demultiplexing circuit 49.
It is sent to each of the terminals a, b, c, d of 51. Regarding the input optical signal of the phase conversion switch 48, H, C, G,
They are exchanged in the order of F and sent by the demultiplexing circuit 50 to the respective terminals e, f, g, h of the subscriber line 51. It should be noted that the replacement of the optical signals on the time axis and the wavelength allocation in the wavelength assignment phase conversion switches 44 and 45 and the replacement of the optical signals in the phase conversion switches 47 and 48 are set according to the connection state of this optical switch. In this embodiment, the connection state shown in FIG. 6 is achieved. Among the optical functional devices used in this embodiment, the phase conversion switch should be composed of a 1 × m optical switch, an m × 1 optical switch and a bistable semiconductor laser according to the conventional example shown in FIG. You can Further, the wavelength gate switch can be composed of the existing optical demultiplexer and optical coupler. Furthermore, since the wavelength assignment phase conversion switch does not need to convert the input optical signal into an arbitrary wavelength, it can be configured according to the phase conversion switch. And since the wavelength gate switch is composed of only passive components, a highly reliable system is provided. In the present invention, the number of different wavelengths corresponding to the number of optical highways is assigned to each optical signal by using the wavelength assignment phase conversion means so that the optical signal is selected by the wavelength gate switch according to the assigned wavelength. And then
This is because it is possible to increase the response speed and increase the line capacity as compared with a simple time division optical switching system. Effects of the Invention As described in detail above, according to the configuration of the present invention, it is possible to realize a high-speed and large-capacity optical switching system by using an optical functional device in a practical stage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram showing a wavelength assignment phase conversion switch showing an embodiment of the present invention, and FIG. 3 is a wavelength showing an embodiment of the present invention. FIG. 4 is a configuration diagram of a gate switch, FIG. 4 is a configuration diagram of a phase conversion switch showing an embodiment of the present invention, FIG. 5 is an operation explanatory diagram of an optical switch showing an embodiment of the present invention, and FIG. FIG. 7 is an explanatory diagram of a connection state, FIG. 7 is an explanatory diagram of a conventional time division multiplex optical switching system, FIG. 8 is an explanatory diagram of a conventionally proposed T-S-T optical switching system, and FIG. It is explanatory drawing of a (lambda) -S (lambda)-(lambda) optical switching system. 1 ... Input side optical highway, 2 ... Wavelength assignment phase converting means, 3 ... Wavelength gate means, 4 ... Output side optical highway, 5 ... Phase converting means.

Claims (1)

(57) [Claims] A plurality of wavelength allocation phase conversion means respectively connected to a plurality of input side optical highways, a wavelength gate means connected to the plurality of wavelength allocation phase conversion means and a plurality of output side optical highways, and a plurality of output side optical means A plurality of phase conversion means respectively connected to the highway, each wavelength allocation phase conversion means, a random switch that distributes the time division multiplexed optical signal from each of the input side optical highways to a plurality of paths for each time slot; A plurality of memory blocks respectively storing the optical signals from the plurality of paths, and a sequential switch for taking out the optical signals stored in the plurality of memory blocks in a predetermined order, each of the memory blocks being Having a plurality of memory cells to which different wavelengths are assigned corresponding to the number of input side optical highways, The wavelength gate means separates the optical signal to which the wavelength is assigned by the wavelength assignment phase conversion means for each wavelength for each of the input side optical highways, and outputs the plurality of output side optical highways to which the respective wavelengths are assigned. An optical switching system in which the phase conversion means outputs the optical signals from the output side optical highways for each time slot.