JPS63105539A - Optical subscriber terminal equipment - Google Patents

Abstract

PURPOSE:To decrease the loss between a subscriber fiber and an optoelectric converter and between the said fiber and an electrooptic converter by using multiplexers/ demultiplexers connected in cascade and photocouplers in place of an photocoupler of 4-input and 1-output. CONSTITUTION:Only the light of wavelength lambda1 passes through between end faces 101 and 102 of a multiplexer/demultiplexer 100 and only the light of wavelength lambda2 passes through between end faces 103 and 102. Only the light of wavelength lambda1 passes through between end faces 105 and 106 of a multiplexer/demultiplexer 104 and only the light of wavelength lambda2 passes through between end faces 107 and 106. A transmission signal is switched by a switch 801 and inputted to either an electrooptic converter 802 or 803, the signal is converted into a optical signal of wavelength lambda1 by the converter 802 and the signal is converted into an optical signal of wavelength lambda2 by the converter 803 and they are led to the subscriber fiber 810 through multiplexers/ demultiplexers 100, 104 via a photocoupler 108 of 2-input/1-output. The optical signal sent to a terminal equipment through the subscriber fiber 810 is given to an optoelectric converter 805 or 808 depending on the wavelength of the signal via a photocoupler 108 and the multiplexer/demultiplexer 104 and one of the output electric signals is selected as a reception signal by a switch 804.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a subscriber terminal optical system accommodated in a space-division optical switch.

(Prior art) Optical fiber transmission systems that use optical fibers as transmission paths have the advantages of being able to transmit a large amount of information because the optical fiber has a wide band, and that the optical fiber is not subject to induced 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 No. 1987-190725 is known.

The optical switch 705 shown in FIG.
Optical subscriber terminals 701 connected by 1 to 744
704 can be connected.

The optical exchange includes 1×3 optical switches 751 to 754 to which subscriber fibers 741 to 744 are connected, and an optical switch 75.
Optical fiber 761 between 1°752 and optical switch 751
, 754, and an optical switch 753.
, 752, and an optical switch 751.
, 753 and the optical switch 752
, 754, and an optical switch 753.
, 754 and an optical fiber 766 between them.

Optical subscriber terminals 701 to 704 have wavelengths λ1. It has two light sources of wavelength λ, and can transmit an optical signal by switching the wavelength of either one. For example, when terminals 701 and 704 communicate, terminal 701 transmits at wavelength λ, terminal 704 transmits at wavelength λ, and as shown by the thick line in FIG. - Optical switch 751. Optical fiber 762-optical switch 754-
By forming a communication path along the path of the subscriber fiber buffer 44, the optical subscriber terminals 701 and 704 can be connected. Note that the terminal 701 transmits at the wavelength λ, and the terminal 701 transmits at the wavelength λ.
04 may be transmitted at wavelength λ. Which terminal transmits at which wavelength is instructed by a subscriber line signal from the control circuit of optical exchange 705 to the control circuit of each terminal before starting communication between the terminals. Alternatively, it may be determined in advance that the calling side terminal transmits at λ1 and the called side terminal transmits at λ.

FIG. 4 shows optical subscriber terminals 701 to 701 in the embodiment of FIG.
704 is a diagram showing a specific example. The transmission signal is switch 8
01 and is input to either the electro-optical converter 802 or 803. When the transmission signal is input to the electro-optical converter 802, it is converted into an optical signal with a wavelength of λ, and when it is input to the electro-optic converter 803, the wavelength is
is converted into an optical signal. Electrical-optical converters 802, 80
The output signal of No. 3 is guided to subscriber line fiber 810 by optical coupler 809. From optical switch to subscriber fiber 81
The optical signal sent to the terminal by the optical coupler 809
The signals are branched by the wavelength filters 806 and 807. The wavelength filter 806 transmits only the optical signal of wavelength λ among the input optical signals, and outputs the optical signal to the optical-electrical conversion circuit 805.
Among the input optical signals, the wavelength filter 807 transmits only the optical signal with wavelength λ, and outputs the optical signal to the optical-to-electrical conversion circuit 806.
Enter. Therefore, the optical-electrical converter 805 converts only the optical signal of wavelength λ8 of the branched output signal of the optical coupler 809 into an electrical signal, and the optical-electrical converter 808
Of the 9 branched output signals, only the optical signal with wavelength λ is converted into an electrical signal. The switch 804 is an optical-to-electrical converter 805°8
08 is selected as the received signal. Therefore, by switching the switches 801 and 804, the transmission wavelength and reception wavelength of the terminal can be changed, and in FIG. 8, the transmission wavelength is λ1 and the reception wavelength is λ.

If the switches 801 and 804 are both reversely switched, the state will be such that the transmitting wavelength is 2 and the receiving wavelength is λ□.

By using different wavelengths for transmission and reception in this way, even if the wavelength component of the own transmitted optical signal mixes into the received optical signal, it can be removed by the action of the wavelength filters 806 and 807.
- It becomes possible to carry out bidirectional communication using the wooden subscriber fiber 841. Furthermore, λ1 is used as the transmission and reception wavelength.
．． Since it is possible to switch depending on the use of either one of λ, communication between arbitrary optical subscriber terminals is possible.

(Problems to be Solved by the Invention) The conventional optical subscriber terminal shown in FIG.
The optical signal passing through 09 is attenuated by at least 6 dB as a loss due to four branching or merging. Therefore, since the received optical signal sent from the subscriber fiber 810 is attenuated by at least 6 dB before reaching the wavelength filters 806 and 807, the opto-electrical converters 805 and 808 need to be of correspondingly high sensitivity. Similarly, the electro-optical converter 802,
Since the transmitted optical signal from 803 is attenuated by at least 6 dB before reaching the subscriber fiber 810, it is necessary to increase the amount of light emitted from the electrothermal-optical converter accordingly.

An object of the present invention is to provide an optical subscriber terminal that does not use an optical coupler and has four power outputs and one output, and to reduce losses between the subscriber fiber and the optical-to-electrical converter and between the electric-to-optical converter.

(Means for solving the problem) The optical subscriber terminal provided by the first invention of the present application converts an input transmission signal into an optical signal of one of two different wavelengths according to a control signal. An electric-to-optical converter emits light from one of two output ends determined for each wavelength, converts the optical signal incident on the two input ends into an electric signal, and selectively selects one of the two according to a control signal. an optical subscriber terminal comprising an optical-to-electrical converter outputting as a received signal, two of each of two output ends of the electric-to-optical converter and two input ends of the optical-to-electrical converter; are connected to two input ends, respectively, and an optical coupler, in which output ends of the two multiplexer/demultiplexers are connected to two input ends, respectively, and a subscriber fiber is connected to the output end. It is characterized by including.

Further, the optical subscriber terminal provided by the second invention of the present application converts an input transmission signal into an optical signal of one of two different wavelengths according to a control signal, and converts the input transmission signal into an optical signal of one of two different wavelengths, and an electric-to-optical converter that outputs from one of the second output terminals, converts the optical signal input to the first and second input terminals into an electrical signal, and selectively receives one of the signals according to a control signal; An optical subscriber terminal comprising an optical-to-electrical converter outputting as a signal, wherein a first output terminal of the electrical-to-optical converter and a first input terminal of the optical-to-electrical converter each have two terminals. a first optical coupler connected to the input end; and a second optical coupler, the second output end of the electrical-to-optical converter and the second input end of the optical-to-electrical converter connected to the two input ends, respectively. and a multiplexer/demultiplexer in which output ends of the first and second optical couplers are respectively connected to two input ends and a subscriber fiber is connected to the output end.

(Function) In the present invention, instead of the optical coupler with 4 manpower and 1 output as described above, cascade-connected multiplexer/demultiplexer and optical coupler are used to connect the subscriber fiber and the optical-to-electrical converter. -Loss between optical converters can be reduced.

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

FIG. 1 is a diagram showing the configuration of an embodiment of the first invention of the present application. FIG. 1 shows a multiplexer/demultiplexer 100 in place of the four-power single-output optical coupler 809 in the conventional subscriber terminal optical system shown in FIG.
, 104 and an optical coupler 108 with two manual outputs and one output are used, and the same numbers as in FIG. 4 represent the same components.

Only light of wavelength λ can pass between the end faces 101 and 102 of the multiplexer/demultiplexer 100, and light of wavelength λ is allowed to pass between the end faces 103 and 102.
Only 100% of light can pass through. Similarly, only light of wavelength λ1 can pass between end faces 105 and 106 of multiplexer/demultiplexer 104, and only light of wavelength λ can pass between end faces 107 and 106. The transmission signal is switched by switch 801 and input to either electrical-optical converter 802 or 803. When the transmission signal is input to the electro-optical converter 802, it is converted into an optical signal with a long wavelength, and then the electro-optical converter 803
When the signal is input to the optical fiber, it is converted into an optical signal with a long wavelength. Electricity
The output optical signals of the optical converters 802 and 803 are sent to the multiplexer/demultiplexer 10.
0 are incident on end surfaces 101, 103, respectively, and are incident on end surfaces 102.
Subscriber fiber 8 via two-power one-output optical coupler 108
Leads to 10. Optical switch to subscriber fiber 810
The optical signal sent to the terminal is input from the end face 106 to the multiplexer/demultiplexer 104 via the optical coupler 108 with two outputs and one output. The multiplexer/demultiplexer 104 sends only the optical signal of wavelength λ1 among the input optical signals from the end face 105 to the optical-to-electrical converter 80.
5, and only the optical signal of wavelength λ is input from the end face 107 to the optical-to-electrical converter 808. Switch 804 is light-
The output electrical signal of either electrical converter 805 or 808 is selected as the received signal.

In this embodiment, between the electro-optical converters 802 and 803 and the subscriber fiber 810, there is a multiplexer/demultiplexer 100 and an optical coupler 10g with two inputs and one output. The loss of the multiplexer/demultiplexer 100 can be reduced to 1 dB or less, and the loss of the optical coupler 108 with 2 manpower and 1 output is about 3 dB of 2 convergence loss, so the sum of both is about 4 dB. The loss can be reduced more than the minimum loss of 6 dB of the output optical coupler. Similarly, subscriber fiber 810 and optical-to-electrical converters 805, 808
In between, there is an optical coupler 108 with two outputs and a multiplexer/demultiplexer 10.
4 exists, and the sum of their losses is about 4 dB, which can reduce the loss compared to the case of using a conventional optical coupler with 4 manpower and 1 output.

Note that in FIG.
Exactly the same effect can be obtained by connecting the input end of 08 to the end face 103 of the multiplexer/demultiplexer 100.

The details of the multiplexer/demultiplexer 100 and 104 in FIG. 1 are described, for example, in the Proceedings of the 1985 National Conference of the Institute of Electronics and Communication Engineers, Volume 10, page 336.

FIG. 2 is a diagram showing the configuration of an embodiment of the second invention of the present application, and the same numbers as in FIG. 1 represent the same components as in FIG. 1. In FIG. 2, the end face of the multiplexer/demultiplexer 205 to which the optical fiber 202 is connected and the subscriber fiber 810
Only light with a wavelength of λ can pass between the end faces where the optical fiber 203 is connected and the end face where the subscriber fiber 810 is connected. It is possible. ', the output optical signal of which the wavelength of the air-to-optical converter 802 is 1 is input to the optical coupler 2o1. The signal is emitted from the optical fiber 2022 through the multiplexer/demultiplexer 205 to the subscriber fiber 810, and the wavelength of the electro-optical converter 803 is λ.

The output optical signal is outputted to a subscriber fiber 810 through a two-power single-output optical coupler 204, an optical fiber 2039, and a multiplexer/demultiplexer 205. Therefore, the electro-optical converter 802
, 803 and the subscriber fiber 810, which is the sum of the losses of the optical coupler 201 or 204 and the multiplexer/demultiplexer 205, can be reduced by 2 dB or more compared to the case of using a conventional optical coupler with four people and one output.

The wavelength-input optical signals input from the optical exchange to the subscriber fiber 810 are sent to the multiplexer/demultiplexer 2o5. The optical signal is input to the optical-to-electrical converter 805 via the optical fiber 2o2° optical coupler 201, and the optical signal with the wavelength λ is sent to the multiplexer/demultiplexer 2o5. optical fiber 203,
The signal is input to an optical-to-electrical converter 808 via an optical coupler 204. Therefore, the loss between the subscriber fiber 810 and the optical-to-electrical converters 805 and 808 is the sum of the loss of the multiplexer/demultiplexer 205 and the optical coupler 201 or 204, which is more than the loss when using a conventional optical coupler with four people and one output. can also be reduced.

(Effect of the invention) According to the present invention, the subscriber fiber and the electrical
An optical subscriber terminal with low loss between the optical converter and the optical-to-electrical converter can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the first invention of the present application,
FIG. 2 is a diagram showing the configuration of an embodiment of the second invention of the present application,
FIG. 3 is a diagram showing the configuration of a space division optical switch, and FIG. 4 is a diagram showing the configuration of a conventional optical subscriber terminal. In the figure, items 801 and 804 are switches, 802 and 80
3 is an electric-to-optical converter; 805 and 808 are optical-to-electrical converters; 100; 104, 205 are multiplexers/demultiplexers, 108, 201, 2
04 is a two-manpower one-output optical coupler, 701 to 704 are terminals, 751 to 754 are optical switches, 705 is an optical exchanger, 8
06 and 807 are wavelength filters, 809 is an optical coupler with 4 power and 1 output, and 810 is a subscriber fiber.

Claims (2)

[Claims] (1) An electro-optical converter that converts an input transmission signal into an optical signal of one of two different wavelengths according to a control signal and outputs it from one of two output ends determined for each wavelength; An optical subscriber terminal comprising an optical-to-electrical converter that converts an optical signal input into two input terminals into an electrical signal and selectively outputs one of the signals as a received signal according to a control signal. Two of the two output ends of the optical converter and two of the two input ends of the optical-to-electrical converter each have two
and an optical coupler in which the output ends of the two multiplexers and demultiplexers are respectively connected to the two input ends and the subscriber fiber is connected to the output end. An optical subscriber terminal featuring: (2) Electricity that converts the input transmission signal into an optical signal of one of two different wavelengths according to the control signal and outputs it from one of the first and second output terminals determined for each wavelength.
It includes an optical converter and an optical-to-electrical converter that converts optical signals input into first and second input terminals into electrical signals and selectively outputs one of them as a received signal according to a control signal. an optical subscriber terminal, a first optical coupler in which a first output end of the electrical-to-optical converter and a first input end of the optical-to-electrical converter are respectively connected to two input ends; a second optical coupler, in which a second output end of the electrical-to-optical converter and a second input end of the optical-to-electrical converter are respectively connected to two input ends; An optical subscriber terminal comprising a multiplexer/demultiplexer in which output ends of couplers are respectively connected to two input ends and subscriber fibers are connected to the output ends.