JPH0666981B2 - Optical switch for WDM signal - Google Patents

Description

TECHNICAL FIELD The present invention relates to a signal exchange (switch) performed between a plurality of input highways and an output highway, and more particularly to an optical switch for wavelength division multiplexed signals.

"Prior Art" To selectively switch one channel signal in one input highway to one channel of one selected output highway between a plurality of input highways and output highways, Conventionally, a time division multiplex switch using an electric signal has been used. (Eg Ba
llard et.al `` The E10.S-TSS.5: A Multipurpose Digit
al Switching System ”ISS′81 Montreal Session 14-
1). That is, as shown in FIG. 8, n pieces of data (communication paths) are time-division multiplexed in each of the electric input highways 1 ₁ to 1 _m , and each input highway 1 _j (j = 1, 2).
...... m) are further m junctions 2 ₁ to 2 _m.
And each of the input highways 1 _j takes out one junctor 2 _i and collects m different junctors to form junctor groups 3 _{1 to} 3 _m . The time-division-multiplexed data in the m junctions of each junction group 3 _j are sequentially written into the data memory RAMs 4 ₁ to 4 _m sequentially using the counter 5 _j .

Based on the address data of each address control memory 6 _j, the data of the same address is read all at once from each of the m RAMs 4 ₁ to 4 _m , and the selector 7 _j causes the address control memory 6 _j to read.
One of these m data is selected based on the addressing of _j . The outputs of the selectors 7 _{1 to} 7 _m are time-divided to the electric output highways 8 ₁ to 8 _m respectively in the RAM 4 _1.
-4 _m will be selected and read.

By the above operation, any electric input highway 1 ₁ to 1 _m
It is possible to switch the data of the arbitrary time slot therein to any time slot in the arbitrary electric output highway 8 ₁ to 8 _m . FIG. 8 shows an example in which the input data D of the i-th time slot of the electric input highway 1 ₁ is output to the k-th time slot of the electric output highway 8 _m .

"Problems to be solved by the invention" This conventional electric time-division switch is capable of non-blocking switching of time-division multiplexed data to a plurality of electric input / output highways, that is, one input channel and output. If there is a space between one of the communication paths, the switch can be switched without being blocked in the switch. A non-blocking switch is a switch that is always sustainable from any incoming line to any free outgoing line, that is, a switch without an internal block, while a switch with an internal block is used from an incoming line because the internal link is in use. It is a switch that may not last on an empty line.

However, although the junction unit is usually constructed by connecting a plurality of printed boards with cables, when high-speed signals are switched, crosstalk of electric signals in the wiring interlacing of the printed boards becomes a problem. Further, when writing the time-division-multiplexed signals to the respective junctions to the RAM 4j, it is necessary to synchronize the time slots between the highways. Therefore, it is necessary to equalize the length of the cable connecting the printed boards and add an elastic memory. There was a problem that it required complicated means.

An object of the present invention is to provide a switch which has less crosstalk, does not lose synchronization of time slots, and is capable of non-blocking switching of high-speed signals.

[Means for Solving the Problems] According to the present invention, the main feature is to perform non-blocking switching by using optical signals wavelength-multiplexed to a plurality of input / output highways. This is different from the conventional technique in that an optical signal is used instead of an electric signal and a wavelength multiplexing method is used instead of time division multiplexing.

According to the present invention, m optical input highways are n
Transmitting wavelength division multiplexed optical signals of wavelength (λ ₁ ... λ _n ),
The optical signal of each optical input highway is branched into m by m optical branching devices. One branch output from each of the m optical branching devices is collected by the optical junction as an optical junction group, and in each of these m optical junction groups, the optical signals from each of the one optical junctions are collected. Signals of arbitrary l (0 ≦ l ≦ n) wavelengths are selectively output as optical signals of arbitrary mutually different wavelengths among λ ₁ to λ _{n by} the optical wavelength selector. The outputs of m optical wavelength selectors belonging to the same optical junction group are respectively multiplexed by an optical multiplexer, and the n wavelength multiplexed optical signals from the m optical multiplexers are respectively converted into m optical output highways. Is output.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention. Optical highways 11 _{1 to} 11 _m configured by optical paths such as optical fibers
N wavelengths (λ ₁ ... λ _n ) of optical signals are wavelength-multiplexed in each of the optical signals, and m optical highways 11 _j (j = 1, 1)
2 ... m) are optical junctions ₁ each of which is composed of, for example, m number of optical fibers using the optical splitters 12 _{1 to} 12 _m.
It is branched into 3 _{1 to} 13 _m . Collect the different m optical junctions, that is, optical highways 11 _{1 to} 11
_The optical junction groups 14 _{1 to} 14 _m are formed by collecting the optical junctions 13 _j in _m . Each optical junction group 14 _j includes n from the optical highways 11 _{1 to} 11 _m.
The same wavelength-multiplexed signals of the waves (λ ₁ ... λ _n ) are input. For each optical junction group 14 _j , this signal is transmitted by the optical wavelength selectors 15 ₁ to 15 _m to its n × m.
Arbitrary n waves in the wave are output as mutually different wavelengths.
Therefore, each of the optical selectors 15 ₁ to 15 _m can select any one of the input n waves of λ _{1 to} λ _n , and the input light of the selected wavelength λ _i can be selected as the wavelength λ _k. Can be converted into output light. That input of the wavelength lambda _i is converted to an output wavelength lambda _j, signal _{l i} waves from the light wavelength selector _{15 j (0 ≦ l i ≦} n) is outputted. In each group of the optical wavelength selectors 15 ₁ to 15 _m , the outputs of the l _{1 to 1 m} waves from the respective selectors are respectively combined by the optical multiplexer 16 _j and output to the optical output highway 17 _j . Each of these optical output highways 17 _{1 to} 17 _m outputs a wavelength multiplexed signal of n waves. That is, the number of output wavelengths of the optical wavelength selectors 15 ₁ to 15 _m is Therefore, the operation of each optical wavelength selector is controlled by a common control unit.

As is apparent from FIG. 1, each optical input highway is connected to all optical output highways via an optical wavelength selector. Therefore, by the above operation, the optical input highway 11
₁ to 11 _m one n waves of any of (λ ₁ ...... λ _n) in the optical output highway ₁₇ 1 to 17 n wave of any of the _m (λ ₁ ...... λ _n) in any of the It can be exchanged (switched) for one wave. That is, an arbitrary n in the input highways 1 ₁ to 1 _m in the conventional switch shown in FIG.
This switch is capable of performing the same operation as connecting one of the speech paths if one of the n speech paths in the output highways 8 ₁ to 8 _m has a vacancy. Can realize non-blocking operation. In the example of FIG. ₁ , the signal D of the wavelength λ _i of the input optical highway 11 ₁ is exchanged with the signal of the wavelength λ _k of the output optical highway 17 _m . Note that n and m are each an integer of 2 or more.

FIG. 2 shows a structural example of an optical wavelength selector which is a main constituent element of the present invention. In FIG. 2, the wavelength division multiplexed optical signal input from the optical junction 13 ₁ which is the optical input unit is fixedly demultiplexed by the optical demultiplexer 22 into n waves of wavelengths λ ₁ to λ _n . The n optical signals are O / E converters 23 ₁ to 23 _n.
Is converted into an electric signal and supplied to the electric switching switch 25. These electric signals are supplied to any one of the E / O converters 24 _{1 to} 24 _n by an electric switching switch 25 which can be realized by a matrix structure, for example. O / E converters 23 ₁ to 23 _n and E / O converter 24 ₁
The switch controller 26 designates the connection state with 24 _n . The n E / O converters 24 _{1 to} 24 _n output optical signals of different wavelengths λ _{1 to} λ _n only when an electric signal is input from the electric switching switch 25. Further, the optical signals from the E / O converters 24 _{1 to} 24 _n are multiplexed by the optical multiplexer 27 and output to the optical output unit 29 ₁ . In this case, the electric switching switch 25 also serves as a selector because it selectively switches 1 (0≤l≤n) of n inputs. With the above operation, an optical wavelength selector that wavelength-converts an n-wavelength input optical signal and outputs an l-wavelength optical signal can be realized. In Fig. 2, λ ₁ is replaced by λ
to _i, the lambda _i to lambda _j, lambda and _n respectively wavelength converted to lambda _1, the converted wave lambda _i, lambda _j, shows an example of output by multiplexing the lambda _1, the wavelength lambda _n light No signal is being output.

Further, in FIG. 3A, the electric input highways 1 ₁ to 1 in FIG.
FIG. 3B shows the time division multiplexing state of data at 1 _m , and the wavelength division multiplexing state of data at the optical input / output highways 11 _{1 to} 11 _m in FIG. ₁ is shown. In the case of transmitting a signal having the same amount of information as in the time division multiplexing method, the pulse width may be n times longer in the present invention. n is the multiplex number and is the third
In the figure, n = 4. Since the present invention performs wavelength conversion, it is not always necessary to synchronize the signals of the series of A ₀ to D ₀ as shown in the figure.

If the switches of the present invention are used in parallel and in multiple stages, a large capacity wavelength division switch can be constructed. For example, as shown in FIG. 4, the wavelength division multiplexing switches of the present invention are connected in parallel and in multiple stages. This can increase the number of channels up to m times. In this case, block may occur. Although FIG. 4 shows a three-stage configuration, generally an S-stage configuration (2 ≦ S) is possible, and the block rate can be reduced as S increases.

[Second Embodiment] FIG. 5 shows a second embodiment of the present invention. In each of the electric input highways 1 ₁ to 1 _m , n pieces of data are time-division multiplexed into time slots t _{1 to} t _n , and these data are multi-wavelength E / O converters 33 _{1 to} 33 _{m, respectively.} Is used for conversion into an optical signal that is wavelength division multiplexed with n wavelengths of λ ₁ to λ _n . In this case converts electric light based on time slots _{t 1} wavelength lambda _{1, t 2} and λ ₂ ...... _{t n} to a corresponding, such as a lambda _n. Each multi-wavelength E / O converter 33 ₁ ~
The output m of 33 _{m is used} as the optical input highways 11 _{1 to} 11 _{m of} the wavelength division multiplexing optical switch 31 described with reference to FIG.
To the optical output highways 17 _{1 to} 17 _m to output optical signals. Each of the optical output highways 17 _{1 to} 17 _m is connected to the multi-wavelength O / E converter 34 ₁
Connect to to 34C _m, time slots _t 1 the optical signal wavelength division multiplexed in the optical wavelength lambda ₁ to [lambda] _n of each highway ~t
_It is converted into an electric signal time-division-multiplexed into _n and output to electric output highways 8 ₁ to 8 _m , respectively. In this case, the wavelength λ ₁ is the time slot t ₁ , the wavelength λ ₂ is t ₂ , and the wavelength λ _n is t _n.
Photoelectric conversion is performed based on such correspondence. By the above operation, an electric signal time-division-multiplexed in any time slot of any electric input highway can be switched to any time slot of any electric output highway.

FIG. 6 shows a configuration example of the multi-wavelength E / O converter. Data time-division multiplexed into time slots of the electrical input highway 1 ₁ In this figure demultiplexed by the demultiplexer 35, the demultiplexed each output is E / O conversion in different wavelengths of lambda ₁ to [lambda] _n, respectively The optical signals are converted into optical signals by the devices 36 _{1 to} 36 _n , then combined by the optical coupler 37, and output to the optical highway 11 ₁ as wavelength division multiplexed outputs.

FIG. 7 shows an example of the configuration of the multi-wavelength O / E converter shown in FIG. In this figure, the data wavelength-division multiplexed on the optical highway 17 ₁ is demultiplexed by the optical demultiplexer 38, and the demultiplexed optical signals of the wavelengths λ _{1 to} λ _n are respectively O / E converters 39.
_The signal is converted into an electric signal at _{1 to} 39 _n , and the electric signal is time-division multiplexed by a multiplexer 41.

[Advantages of the Invention] As described above, according to the present invention, since the junction portion is the optical fiber wiring, crosstalk can be reduced. The second
The changeover switch unit shown in the figure is an electric circuit, but since it processes a low-speed signal that is not multiplexed, it has less crosstalk than the time division system of FIG.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a configuration example of the wavelength selector in FIG. 1, and FIG. 3 is a conventional electric input highway and the optical input highway of the present invention. And FIG. 4 is a block diagram showing the structure of a large capacity optical switch using the wavelength multiplexing signal optical switch shown in FIG. 1, and FIG. 5 is the wavelength multiplexing of the present invention. A block diagram showing an example in which a signal optical switch is inserted in a time division multiplex highway, FIG. 6 is a block diagram showing a concrete example of the multiple wavelength E / O converter in FIG. 5,
5 is a block diagram showing a concrete example of the multi-wavelength O / E converter in FIG. 5, and FIG. 8 is a block diagram showing a conventional time division multiplex electric switch. 11 _{1 to} 11 _m : optical input highway, 12 _{1 to} 12 _m :
Optical branching device, 13 _{1 to} 13 _m : Optical junction, 14 ₁ to 1
4 _m : Optical junction group, 15 ₁ to 15 _m : Optical wavelength selector, 16 _{1 to} 16 _m : Optical multiplexer, 17 ₁ to 1
7 _m: optical output highway, 22: optical demultiplexer, ₂₃ 21 to
3 _m : O / E converter, 24 _{1 to} 24 _m : E / O converter,
25: electric switching switch, 26: switch control circuit,
27: Optical multiplexer, 31: Optical switch for wavelength multiplexed signal, 3
3 _{1 to} 33 _m : multi-component wavelength E / O converter, 34 _{1 to} 3
4 _m : Multiple wavelength O / E converter.

Claims (1)

[Claims] 1. An n (n is an integer of 2 or more) wavelength (λ ₁ to
λ _n ) m optical input highways (m is an integer of 2 or more) through which optical signals wavelength-division-multiplexed are transmitted, and m optical input highway optical signals are each branched into m optical signals. M of the optical branching device incident on the optical junction of the book
, And m to which the branched optical signals from these m optical branching devices are input.
M optical junction groups each consisting of m optical junctions collected from each optical junction, and connected to each of the m optical junctions of each optical junction group. demultiplexes the emitted light into n optical signals of lambda ₁ to [lambda] _n in the optical demultiplexer, these n optical signal is converted into an electric signal each, any of these n pieces of electrical signals by the changeover switch L (0 ≦ l ≦ n)
Are supplied to different ones selected from n electro-optical converters for converting into optical signals of wavelengths λ ₁ to λ _n , and optical signals are multiplexed from these n electro-optical converters. ² and m optical wavelength selectors emitted multiplexes in vessels, m the same optical multiplexer for multiplexing the output light signal from the optical junk data connected to the group the m number of the optical wavelength selectors
An optical switch for wavelength-division-multiplexed signals, which is composed of a plurality of optical output highways into which the respective outgoing lights are incident from these m optical multiplexers.