JPS6248895A - Space dividing light exchange system - Google Patents

Abstract

PURPOSE:To attain a direct connection between terminals without using a wavelength conversion device by providing light sources having different wavelengths with each other on each of subscriber's terminals and allocating different transmission wavelengths with each other on each of the terminals in the setting of a channel. CONSTITUTION:Each of subscriber's terminals 101-104 has two light sources having the wavelengths of lambda1 and lambda2, enabling a transmission with switching an optical signal of either one wavelength. For example, when a communication is performed between the terminal 101 and 104, the terminal 101 transmits with a wavelength of lambda1 and the terminal 104 with that of lambda2 and also, by forming the channel in the route of a subscriber fiber 341 optical switches 351 and 354 a subscriber fiber 344 by a light exchanger 105, a connection between the terminals 101 and 104 can be obtained. At such a time, so that a wavelength exchanger is not required between the terminals 101 and 104, the communication can be performed with an optical signal of optical signal speed/modulation system. Besides, the communication in such a way that the terminal 101 transmits with the wavelength of lambda2 and the terminal 104 with that of lambda1 causes no trouble.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a space division optical switching system that connects arbitrary subscriber terminals among a plurality of subscriber terminals using optical signals.

(Prior art) Optical fiber transmission systems that use optical fibers as transmission paths have the advantages of being able to transmit large amounts of information because the optical fibers have a wide band, and that the optical fibers are not subject to dielectric noise. Therefore, it is expected that it will be widely used in the future. In addition to this optical fiber transmission system, it is desirable to use an optical switching system that can exchange optical signals in the optical domain without converting optical signals into electricity and exchanging them using electric circuits. As such a space-division light exchange system, a space-division light exchange system as shown in FIG. 3 and described in Japanese Patent Application Laid-Open No. 78267/1984 has been known.

The optical switch 305 shown in FIG.
Terminals 301 to 304 connected by 1 to 344
It is possible to connect any two of them. The optical exchange includes 1×3 optical switches 351 to 354 to which subscriber fibers 341 to 344 are connected, a wavelength converter 361 between the optical switches 351 and 352, and a wavelength converter 362 between the optical switches 351 and 354. A wavelength converter 363 between optical switches 353 and 352, a wavelength converter 364 between optical switches 351 and 353, a wavelength converter 365 between optical switches 352 and 354, and a wavelength converter 366 between optical switches 353 and 354. It is composed of Wavelength converters 361-36
6 converts the optical signal of wavelength λ1 input from one end face to λ2
It has the function of converting the wavelength to the wavelength of , and outputting it from the other end face. Similarly, it also has the function of wavelength converting an optical signal of wavelength λ1 inputted from the other end face to a wavelength of λ2 and outputting it from one end face. The terminal 301 includes an electrical-to-optical converter 311 that converts an electrical signal to be transmitted into an optical signal with a wavelength of λ.
, an optical-to-electrical converter 321 that converts an optical signal input from the subscriber fiber 341 into an electrical signal, and an optical signal with a wavelength λ1 from the electrical-to-optical converter 311 to the subscriber fiber 34.
1 and from the optical switch 305 to the subscriber fiber 341.
Select the optical signal of wavelength λ2 guided through the optical
It includes a multiplexer/demultiplexer 331 that sends out data to an electrical converter 321 . Similarly, the other terminals 302 to 304 have electrical-to-optical converters 312 to 314, optical-to-electrical converters 322 to 324,
It includes branch waves 5332 to 334.

In this way, when performing bidirectional communication using one subscriber fiber 341, in order to prevent the reflected component of the own transmitted optical signal from being mixed into the received optical signal at the optical-to-electrical converter 321, , transmitting and receiving using different wavelengths of λ1 and λ2,
As a result, the reflection component of the transmitted optical signal of wavelength λ1 is removed by the multiplexer/demultiplexer 331 provided before the optical-to-electrical converter 321, and only the received signal of wavelength λ1 is optical-to-electrically converted. When the terminals 301 and 304 communicate, as shown by the bold line in FIG. 331, a subscriber fiber 341, and an optical switch 351 to one end of the wavelength converter 362. The optical signal with the wavelength λ1 is wavelength-converted into the wavelength λ2 by the wavelength converter 362, and then input to the optical-to-electrical converter 324 through the optical switch 354, the subscriber fiber 344, and the multiplexer/demultiplexer 334, where it becomes an electrical signal. is converted to On the other hand, terminal 30
4 to the terminal 301 is sent from the electrical-to-optical converter 3
14, it is converted into an optical signal of wavelength λ1, and is sent to a multiplexer/demultiplexer 334.
, subscriber fiber 344 and optical switch 354 to the other end of wavelength converter 362 . Wavelength conversion 536
2, this optical signal of wavelength λ1 is wavelength converted into oil, and then sent to an optical switch 351, a subscriber fiber 341, and a multiplexer/demultiplexer 3.
31, the signal is input to an optical-to-electrical converter 321 and converted into an electrical signal. In this way, within the optical exchanger 305, the wavelength λ
By performing wavelength conversion between λ1 and λ2, terminals having the same transmitting wavelength and receiving wavelength can communicate with each other.

FIG. 4 is a diagram showing the configuration of wavelength converters 361 to 366 in FIG. 3. Among the optical signals inputted from the fiber 401, an optical signal having a wavelength λ1 is selected by the multiplexer/demultiplexer 402 and inputted to the wavelength conversion device 403. The wavelength conversion device 403 converts the input optical signal of wavelength λl to wavelength λ2. The wavelength-converted optical signal of wavelength λ2 is now.

It is guided to a fiber 406 by a demultiplexer 405 . On the other hand, an optical signal with a wavelength λ1 among the optical signals inputted from the fiber 406 is selected by the multiplexer/demultiplexer 405 and inputted to the wavelength conversion device 404. The wavelength conversion device 404 converts the input optical signal of wavelength λ1 into wavelength λ2. The wavelength-converted optical signal of wavelength λ2 is guided to fiber 401 by multiplexer/demultiplexer 402. Examples of the wavelength conversion devices 403 and 404 in FIG.
of Quantum Electronics) QE
- pnp described in volume 14, issue 11, pages 810-813
A composite element of an n-structure photodetector and a light emitting diode can be used.

(Problems to be Solved by the Invention) The maximum operating frequency of such a wavelength conversion device using a composite device of a pnpn structure light receiving element and a light emitting diode is about 100 MHz, and high-speed optical signal conversion of 100 MHz or higher is impossible. Can not. Furthermore, since it has the characteristic of S-type negative resistance, the relationship between the amount of input light and the amount of output light is nonlinear, and it is also impossible to exchange optical signals intensity-modulated with analog signals. In this way, in the space-division optical switching system using a wavelength conversion device, there are limitations on the speed and modulation method of optical signals communicated between terminals.

An object of the present invention is to provide a space division optical switching system that does not use a wavelength conversion device, and to enable communication between terminals at any speed and any modulation method.

(Means for Solving the Problem) In the space division optical switching system of the present invention, each subscriber terminal is provided with at least light sources with different wavelengths, and when setting a communication path, the called subscriber terminal and the calling subscriber terminal have different wavelengths. It is characterized by assigning transmission wavelengths.

(Function) In the present invention, as described above, by preparing a light source of two wavelengths at the terminal and using one of the optical signals of the two wavelengths as the transmission wavelength, the optical exchange can intervene with a wavelength conversion device. It is sufficient to directly connect the terminals without any need for communication between the terminals, and the terminals can communicate using optical signals of any signal speed and modulation format.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

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

The same numbers in Figure 1 as in Figure 3 refer to Figure 3.
Represents the same components as in the figure. In FIG. 1, the optical exchange 105 removes the wavelength converters 361 to 366 in the optical exchange 5305 in FIG. 3 and directly connects the optical switches 351 to 354. It has two light sources, and the optical signal of either wavelength can be switched and transmitted. For example, when terminals 101 and 104 communicate, terminal 101 uses wavelength λ
1, and the terminal 104 transmits at the wavelength λ2, and the exchange 105 forms a communication path from the subscriber fiber 341 to the optical switch 351.354 to the subscriber fiber 344, as shown by the thick line in FIG. Terminal 101
．． 104 can be connected. At this time, terminal 10
Since no wavelength converter is required between 1.104 and 1.104, communication is possible with optical signals of any signal speed and modulation method. In addition,
Terminal 101 transmits at wavelength 2, and terminal 104 transmits at wavelength λ1.
It is okay to send it by . The optical switch 1 determines which terminal transmits at which wavelength before starting communication between the terminals.
05 control circuit to each terminal's control circuit by a subscriber line signal. Alternatively, it may be determined in advance that the calling side terminal transmits at λ1 and the called side terminal transmits at λ2.

FIG. 2 shows the terminals 101 to 101 in the embodiment of the present invention shown in FIG.
104 is a diagram showing a specific example. The transmission signal is switch 2
01 and is input to either the electrical-optical exchanger 202 or 203. When the transmission signal is input to the electric-to-optical exchanger 202, it is converted into an optical signal of wavelength λ1, and when input to the electric-to-optical exchanger 203, it is converted to an optical signal of a different wavelength. The output optical signals of the electro-optical exchangers 202, 203 are guided by an optical coupler 209 to a subscriber line fiber 210. From optical switch to subscriber fiber 21
The optical signal sent to the terminal by the optical coupler 209
The signals are branched and input to wavelength filters 206 and 207. The wavelength filter 206 transmits only an optical signal having the same wavelength λ1 as the input optical signal and inputs it to the optical-to-electric conversion circuit 205, and the wavelength filter 207 transmits only the optical signal having the same wavelength λ2 as the input optical signal. Input to the optical-electrical conversion circuit 206. Therefore, the optical-electrical converter 205 converts only the optical signal having the same wavelength λ1 of the branched output signal of the optical coupler 209 into an electrical signal, and the optical-electrical converter 208
Only the optical signal having the same wavelength λ2 of the branched output signal is converted into an electrical signal. Switch 204 is an optical-to-electrical converter 205.20
8 selects one output electrical signal as the received signal. In this way, the transmission wavelength and reception wavelength of the terminal can be changed by switching the switches 201 and 204. In FIG. 2, the transmission wavelength is λ1 and the reception wavelength is 2. If both switches 201 and 204 are switched in the opposite direction, the state will be such that the transmission wavelength is λ2 and the reception wavelength is λ1.

(Effects of the Invention) As described above, according to the present invention, a space division optical switching system that does not use a wavelength conversion device is obtained, and communication between terminals at any speed and using any modulation method is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a specific example of terminals 101 to 104 in FIG. 1, FIG. 3 is a diagram showing a conventional space-division optical switching system, and FIG. 3 is a diagram showing the configuration of wavelength converters 361 to 366 in FIG. 3. FIG. In the figure, 101 to 104. 301 to 304 are terminals,
105゜305 is an optical exchange, 210.351-354 is an optical switch, 201゜204 is a switch, 202.20
3.311.314 is an electro-optical converter, 205.208
．． 321.324 is an optical-electrical converter, 206°207 is a wavelength filter, 209 is an optical coupler, 331.334°4
Reference numerals 02 and 405 represent multiplexers/demultiplexers, 361 to 366 represent wavelength converters, and 403 and 404 represent wavelength converter devices, respectively.

Claims (1)

[Claims] A space-division optical switching system characterized in that each subscriber terminal is provided with at least a light source having a different wavelength from each other, and different transmission wavelengths are assigned to a called subscriber terminal and a calling subscriber terminal, respectively, when setting up a communication path.