JPS5811563B2 - Hikari Eye Bar Tsuushin Houshiki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber communication system having a function of detecting a location where a failure occurs in an optical fiber.

Signal transmission systems using optical fibers, which have various characteristics such as broadband performance, low susceptibility to electromagnetic interference, and good electrical insulation, are the latest technology for low-loss fibers and electrical-to-optical and optical-to-electrical conversion. Due to rapid progress in the development of devices, it suddenly came into the spotlight.

This is particularly attractive in power communications, which have many sources of electromagnetic interference, and some power companies have already begun practical tests.

By the way, in order to facilitate the realization of optical fiber communication systems, it is of course necessary to further improve the performance of optical fibers, but at the same time, it is necessary to develop efficient systems, that is, to transmit information economically and reliably. It is necessary to be able to transmit.

The present invention has been made in view of the above points, and while the conventional experimental method uses a pair of optical fiber transmission lines for transmission and reception, the present invention allows transmission and reception of light energy in the direction of propagation in the optical fiber. Taking advantage of its stability, we can reduce the cost of the system by allowing communication in both directions to occur simultaneously through a single optical fiber, and at the same time, when a failure occurs within the optical fiber, the transmission loss increases and the light becomes the point of failure. Taking advantage of the fact that the received signal is reflected at The present invention aims to promote the realization of optical fiber communication systems by providing a highly reliable communication system that also has a function for detecting failure points.

Next, the present invention will be explained in detail using the drawings.

The figure is a block system diagram of an embodiment of the present invention.

In the figure, 1 is an optical fiber, and an A station and a B station, which will be described below, are coupled to both ends of the optical fiber.

In station A, 2 is a data transmission circuit, 3 is a test pulse generation circuit, 4 is a transmission changeover switch element, and 5 is an optical transmitter that converts an electrical signal into an optical signal and transmits it. The contact c is always on the contact a side, and applies the output of the data transmission circuit 2 to the optical transmitter 5. Also, if a local failure such as a break or clouding occurs in the optical fiber 1, the reception level monitoring circuit 9, which will be described later, detects this. When the reception level drops below a certain value, the switch is switched to the contact side, and the output of the test pulse generating circuit 3 is applied to the optical transmitter 5.

6 is a well-known half mirror; 17 is an optical receiver that converts an optical signal into an electrical signal and sends it out; 8 is a gain control circuit thereof; It is controlled by the output of the circuit 3 and greatly reduces the receiving sensitivity of the optical receiver 7 during these transmissions, preventing a part of the transmitted signal from leaking to the optical receiver 7 side at the half mirror 6 and being received at the own station. For example, the information transmission reliability is prevented from decreasing.

9 is a reception level monitoring circuit, 10 is a reception changeover switch element, 11 is a pulse regeneration circuit, 12 is a data reception circuit, 13
is a pulse interval display circuit, and the reception level monitoring circuit 9
constantly instructs the output level of the optical receiver 7, making it possible to monitor the quality of the optical fiber transmission path and preventing a drop in information transmission reliability.

Further, when the reception level drops below a certain value due to the occurrence of a failure in the optical fiber 1, an output is sent out.

Simultaneously with the control of the transmission changeover switch element 4 described above, the reception changeover switch element 10 is controlled to switch its contact c from the contact a side to the contact b side, and the output of the optical receiver 7 which is applied to the pulse regeneration circuit 11 is is added to the pulse interval display circuit 13.

In addition, the pulse interval display circuit 13 receives as input the pulse P2 from which the test pulse is reflected at the point of failure and returns to the optical receiver 7 when a failure occurs in the optical fiber 1, and the output pulse P1 of the test pulse generation circuit 3. It displays the pulse time interval of Pl and P2, and detects the location of a failure in the optical fiber 1 from this.The delay circuit 1
4, the time relationship is pre-adjusted.

Next, in the B station, 15 is a data transmitting circuit, 16 is an optical transmitter, 17 is a half mirror, 118 is an optical receiver, 19 is a gain control circuit, 20 is a pulse regeneration circuit, and 21 is a data receiving circuit. The function of the circuit is similar to that of station A.

Reference numeral 22 denotes a reception level monitoring circuit, which constantly instructs the optical receiver 1B to measure the level, makes it possible to monitor the transmission quality in the optical fiber 1, prevents a decrease in information transmission reliability, and at the same time, monitors the level of the optical receiver 1B. When the optical fiber 1 is thought to have a failure due to the drop being below a certain value, an output is sent out to stop the data transmission of the data transmission circuit 15.

The above is the configuration of the embodiment of the present invention.

Next, its operation will be explained.

[A] Information transmission operation When transmitting information from station A to station B, the output of the data transmission circuit 2 passes through the transmission changeover switch element 4 to the optical transmitter 5.
The data signal is converted into an optical signal.

The signal is then coupled to the optical fiber 1 by the half mirror 6 and transmitted.

At station B, a half mirror 17 is used to transmit the optical signal to the optical receiver 1.
8, where the optical signal is converted back into an electrical signal, and then pulse-shaped by the pulse regeneration circuit 20 and sent to the data reception circuit 20.
Put it in.

Next, in the case of information transmission from station B to station A, the output of data transmission circuit 15 is converted into an optical signal by optical transmitter 16, and then coupled to optical fiber 1 using half mirror 17.

At the A station, a half mirror 6 guides the optical signal from the B station to an optical receiver 7 to convert it back into an electrical signal, and then inputs it through a reception selector switch element 10 to a pulse regeneration circuit 11, where it is pulse-shaped and converted into data. into the receiving circuit 12.

As described above, information can be transmitted in both directions simultaneously using one optical fiber at all times.

In this case, in order to prevent a part of the transmitted output from entering the receiving circuit of the local station via the half mirror and reducing the reliability of information transmission, the optical pulse information of both half mirrors 6 and 17 is set so that they do not match. It is preferable to control the reception sensitivities of the optical receivers 7 and 12 in time-coordinated manner and in synchronization with the data transmission time or reception time using the gain control circuits 8 and 19.

[B] Fault point detection operation If a local fault occurs such as a break in the optical fiber 1 or clouding due to surrounding conditions, the transmission loss will clearly increase and the optical reception level will drop, and furthermore, if a local fault occurs such as a break in the optical fiber 1 or cloudy When a pulse of light is applied, the light is reflected.

The reception level monitoring circuits 9 and 22 of the A and B stations measure the output levels of the optical receivers 7 and 18 to constantly monitor the transmission line loss of the optical fiber 1, thereby preventing a drop in information transmission reliability.

If the level monitoring value falls below a certain value and it is thought that a local failure such as a break has occurred, the level monitoring circuit 9 sends out an output to the transmission changeover switch element 4 and the reception changeover switch element 10. , thereby connecting the test pulse circuit 3 to the optical transmitter 5 and connecting the optical receiver 7 to the pulse interval display circuit 13.

Furthermore, the output of the level monitoring circuit 22 causes the data transmission circuit 15 to stop transmitting.

Then, the pulse signal from the test pulse generation circuit 3 is converted into an optical pulse by the optical transmitter 5 and applied to the optical fiber 1, and this optical pulse is reflected from the faulty part and passes through the half mirror 6 to the optical receiver 7. enter.

Then, the electric signal greatly amplified here enters the pulse interval display circuit 13 via the switched switch element 10, where the time relationship is compared with the pulse directly input from the test pulse generation circuit 3. The time difference indicates at what distance from the starting end of the optical fiber 1 on the A side side the failure has occurred.

As explained above with the embodiments, the present invention can perform communication in both directions at the same time using one optical fiber, which is more economical than the conventionally proposed method using two optical fibers. Since a part of the transmitter/receiver circuit is used to constantly monitor the quality of the forward transmission path and detect the location of failure, it is possible to perform highly reliable optical fiber communication with an economical system.

In addition, in the above example, considering the case where the optical fiber is short,
A test pulse for detecting the fault location was emitted from station A, but if the optical fiber is long, station B should have the same configuration as station A, and test pulses would be sent from both ends to the optical fiber. Good too.

As is clear from the above description, according to the present invention, an economical and highly reliable optical fiber communication system can be obtained, and the practical effects are great.

[Brief explanation of the drawing]

The figure is a block system diagram of an embodiment of the present invention.

Claims (1)

[Claims] 1 A transmission/reception circuit consisting of a transmission system consisting of a data transmission circuit and an optical transmitter, and a reception system consisting of an optical receiver whose reception sensitivity is reduced during transmission, a data reception circuit, and a level monitoring circuit of the optical receiver is half mirrored. - are connected to both ends of a single optical fiber via a A generating circuit and a pulse interval display circuit are provided in one or both of the transmitting and receiving circuits, and when the detection level of the level monitoring circuit of the transmitting and receiving circuit falls below a certain level corresponding to the occurrence of a fault, the data transmitting circuit is set for testing. The pulse generating circuit and the data receiving circuit are switched to the pulse interval display circuit, and a test optical pulse is sent to the optical fiber, and the reflected light pulse from the fault location and the test pulse are added to the pulse interval display circuit to detect the fault. An optical fiber communication method characterized by detecting the location of occurrence.