JPS60178724A - Optical fiber cable communication equipment - Google Patents

Abstract

PURPOSE:To reduce the cost and also to improve the reliability of an optical fiber cable communication equipment by securing such a constitution where the breakage of an optical fiber cable can be detected accurately just by having a double structure of an optical conversion part. CONSTITUTION:Plural pieces of information delivered from a relay device 1 are modulated by plural PCM modulating/demodulating devices 2 and then multiplexed by a multiplexing circuit 3. The output of the circuit 3 is converted into transmission optical signals W1 and W2 by electrooptic converters 4a and 4b having optical outputs of different wavelengths. Then both optical signals are synthesized by a multiplexing circuit 10 and transmitted to a communication equipment 8' of a terminal at the remote side via an optical fiber cable 9 to be separated again into signals W1 and W2 by a demultiplexing circuit 11. These optical signals are converted into electric signals by photoelectric converters 5a and 5b. Here the AND output obtained when the outputs of optical level drop detectors 7a and 7b are used as the double input of an AND circuit 13 is obtained only in case the cable 9 is broken or the double structure and the separation system between converters 4a and 4b as well as 5a and 5b have faults at a time. The probability is very small with the latter case and therefore the breakage of the cable 9 can be detected in the form of an output signal of the circuit 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to detection of breakage of an optical fiber cable 7' applied to an optical fiber cable communication device of a power transmission line protection relay device of a power system.

[Prior art]

A conventional communication device of this type has a configuration shown in FIG.

In Fig. 1, 1 is a power transmission line protection relay device (hereinafter referred to as a relay device), 2 is a pulse code modulation (PCM) L, which demodulates the transmission signal from the relay device 1, and a PCM modulator/demodulator that demodulates the transmission signal from the relay device 1. 3
is a multiplexing circuit that multiplexes and demultiplexes the output signals of a plurality of PCM modulators 2; 4 is an electro-optic converter that converts the output electrical signals of the multiplexing circuit 3 into optical signals; and 5 is an electrical optical converter that converts the optical signals into electrical signals. 6 is an error detector that detects code errors and loss of synchronization during signal demodulation of the PCM modem 2; 7 is an optical level drop detector 8 that detects and monitors the output of the photoelectric converter 5; 1 is an optical communication device constituted by the above components 2 to 7, etc., and 9 is an optical fiber cable.

Next, the operation will be explained. Multiple pieces of current information output from the relay device 1 (current flow direction or its polarity,
instantaneous values, etc.) are each pulse code modulated by a plurality of PCM modulators 2, and are further pulse code modulated by a multiplexing circuit 3.
A plurality of PCM signals from the PcM modulator/demodulator 2 are multiplexed, and then converted into optical signals by the electro-optic converter 4 and transmitted to the other end via the optical fiber cable 9. A similar device is also installed at the other end, and the optical signal transmitted through the optical fiber cable 9 is converted into a light signal by the opto-electrical converter 5, and is further converted into a plurality of PCM signals (by the multiplexing circuit 3). = separated and demodulated by the PCM modulator 2, and the current information of the other end is received by the relay device 1.

If an abnormality occurs in the transmission system, the current information will be erroneously transmitted to the other end, and the relay device 1 will operate in error (=). In order to prevent the relay device 1 from operating due to Alternatively, a lock signal is output directly to the relay device 1.

Incidentally, since the optical fiber cable 9 is generally installed alongside a power transmission line tower or is often built into the power line cable itself, it is conceivable that the optical fiber cable 9 may break at the same time as a system failure of the power transmission line. At this time, the above-mentioned error detector 6 should operate as the relay device 1.
In this case, an error in the code due to the breakage of the optical fiber cable 9 and a loss of synchronization are detected and the relay device 1 becomes inoperable. As a countermeasure for this, the light level drop detector 7
(It detects that the second light reception level has decreased, determines this as a breakage of the optical fiber cable 9, disables the detection of the error detector 6, and activates the relay device 1 which has been made inoperable. That is what is being considered.

Since the conventional device is configured as described above, current information may be erroneously transmitted due to a drop in optical level due to an abnormality in a transmission system other than the optical fiber cable 9, such as the electro-optic converter 4 or the photo-electric converter 5. Even light level drop detector 7
is activated, invalidating the detection by the error detector 6, which has the disadvantage that the relay device 1 may operate erroneously even if there is no abnormality in the optical fiber cable 9.

[Summary of the invention]

The present invention has been made in order to eliminate the above-mentioned drawbacks of the prior art, and convert the output electrical signal from a multiplexing circuit into a plurality of transmitted optical signals 1 of different wavelengths by a plurality of electro-optical converters. This is combined and multiplexed by a multiplexer, transmitted through two optical fiber cables, and the levels of multiple transmitted optical signals of different wavelengths separated by a demultiplexer are compared to determine the breakage of the optical fiber cable. It is an object of the present invention to provide an optical fiber cable communication device that can detect.

[Embodiments of the invention]

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

FIG. 2 shows a case where the output electrical signals from the multiplexing circuit 3 are duplicated. 4a and 4b are electro-optic converters that transmit transmission optical signals W, , W, which have different wavelengths, and 10 is a two A multiplexer 11 for combining transmission optical signals Wt, W having different wavelengths is a multiplexer 11 for combining transmission optical signals W1 . 5a and Lb are photoelectric converters, 7a and 7b are optical level drop detectors, 12 is an OR circuit, and 13 is an AND circuit showing an example of a comparator. be.

Next, I will explain the operation in two parts. The output electrical signal from the multiplexing circuit 3 is sent to an electro-optical converter 4 having optical outputs with different wavelengths.
a, 4b into transmission optical signals Wt, Wz, which are combined by a multiplexer 10 into one optical fiber cable 9.
The data is then transmitted to the communication device 8' at the other end. The transmitted combined transmission optical signal is separated again into two types of transmission optical signals Wl and Wx by the demultiplexer 11 at the other end, and each is converted into a stain signal by the opto-electrical converter 5a15b. Since they are the same signals, the OR circuit 12 can obtain the received signal.

Here, when the outputs of the optical level drop detectors 7a and 7b are made by the two operators of the AND circuit 13, the AND output is generated when the optical fiber cable 9 is broken or when the two electro-optic converters 4a and 4
This is only the case when the duplication and separation system of b or the two photoelectric converters 5a and 5b becomes abnormal at the same time. By the way, the probability that the duplication and separation systems will be abnormal at the same time is very small, so when the output signal of the AND circuit 13 is generated, it indicates that the optical fiber cable 9 has broken as well as a system failure of the power transmission line. There is.

In this way, the AND circuit 1
Therefore, when an output signal is generated from the AND circuit 13, it can be detected as the output signal of the circuit 2-detector 6.
By disabling the detection, the relay device 1 can be operated.

In the above embodiment, only the optical communication device 8 on the left side in FIG. 2 is duplicated with two different wavelengths from the optical communication device 8' on the right side. may have exactly the same configuration (2) and multiplex transmission in both directions.

〔Effect of the invention〕

As described above, according to the present invention, the breakage of the optical fiber cable can be reliably detected simply by duplicating the optical conversion part, so the device can be made inexpensive and highly reliable. It has a remarkable effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional optical fiber cable communication device, and FIG. 2 shows the configuration of an optical fiber cable communication device according to an embodiment of the present invention. 5b...Photoelectric converter, 7a, 7b
... optical level drop detector, lO... multiplexer, 11.
... splitter, 13... comparator. Patent applicant: Mitsubishi Electric Corporation r--1

Claims (1)

[Claims] a plurality of electro-optic converters that convert electrical signals into a plurality of transmission optical signals with different wavelengths; a multiplexer that combines the plurality of transmission optical signals with different wavelengths from the electro-optical converters; a demultiplexer that separates a combined transmission optical signal via an optical fiber cable; a plurality of opto-electrical converters that convert the plurality of transmission optical signals with different wavelengths separated by the demultiplexer into electrical signals; A fiber optic cable communication device comprising: a plurality of optical level drop detectors that detect output signals of opto-electrical converters; and a comparator that compares the plurality of detection signals from the optical level drop detectors.