JPH09289494A - Line monitoring device for wavelength multiplex optical submarine cable network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the line monitoring device which can monitor the wavelength multiplex optical submarine cable network. SOLUTION: An optical transmitter of a transmission-side terminal station device 1a of a station A receives a modulated signal from the line monitoring device 11, superposes it as a line monitor signal on a light signal, and outputs them to a repeating line. The line monitor signal which is sent back through the return line of each optical repeater inserted into the repeating line is demultiplexed by an optical coupler 23 and inputted to the line monitoring device 11. An optical selector 12 selects a feedback signal from each fiber couple. An array waveguide grating type filter 14 divides the selected wavelength multiple light signal into wavelengths λto λn and a selector 15 selects signals of the wavelengths, one by one. A photodetection part 16 performs photoelectric conversion and a demodulation part 17 demodulates the fed-back line monitor signal. A correlation part 18 checks whether or not there is abnormality in the line monitor signal to monitor whether or not trouble occurs to the repeating line. When the line monitoring of one fiber couple is completed, the line of a next fiber couple begins to be monitored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line monitoring device for a wavelength division multiplexed optical submarine cable network, and more particularly to an optical device incorporating a plurality of transmission terminal stations, line monitoring devices, and optical loopback circuits having different transmission wavelengths. A submarine repeater, an optical submarine cable, and a wavelength-multiplexed optical submarine cable network including an optical submarine branching device that adds / drops a specific wavelength can monitor all transmission lines in the optical submarine cable network. The present invention relates to a line monitoring device for a wavelength division multiplexing optical submarine cable network.

[0002]

2. Description of the Related Art Optical submarine cable networks are generally long-distance and most of them are installed on the seabed, so that a failure of the network may affect communication between transmitting terminal equipment. In some cases, it is necessary to pinpoint the location of the fault and repair the fault. The optical fiber cable itself and the optical repeater can be considered as places where a failure may occur in the network, but it is said that the possibility that the optical fiber cable itself will fail is small. Therefore, the conventional line monitoring device for an optical submarine cable network is configured as shown in FIG.

In the figure, 31 and 32 are the transmitting side and the receiving side of the first transmitting terminal station device, respectively, and 33 is a line monitoring device (LME). Further, 34 and 35 are the receiving side and the transmitting side of the second transmission terminal station device, respectively, and 36 is a line monitoring device (LME). In addition, 37 is an upstream line, 3
Reference numeral 8 is a down line, and one fiber pair is constituted by these. A plurality of optical repeaters are inserted in the upstream line 37 at predetermined intervals, and an optical amplifier 40 is provided in each optical repeater.
a, 40b, 40c are provided. Similarly, a plurality of optical repeaters are inserted in the down line 38 at predetermined intervals,
Each optical repeater is provided with optical amplifiers 41a, 41b, 41c. In addition, each optical amplifier 40a, 40b, 40c
The folded lines 42a, 42b, 42c are provided between the output side of each of the optical amplifiers 41a, 41b, 41c and the output side of each of the optical amplifiers 41a, 41b, 41c.

In the optical submarine cable network having such a configuration, the transmission terminal equipment on each transmitting side superimposes on the optical signal for communication and sends out the line supervisory signal. The line monitoring signal is returned to the lines on the other side by the folded lines 42a, 42b, 42c, and the line monitoring signal output from the transmission terminal device 31 is received by the line monitoring device 33. On the other hand, the line monitoring signal output from the transmission terminal device 35 is received by the line monitoring device 36. Track monitoring device 33
And 36, depending on the reception time of the received line monitoring signal,
It is possible to identify from which turn-back line it is turned back. Therefore, when an abnormality occurs in the optical submarine cable network, the line monitoring devices 33 and 36
It is possible to identify which optical amplifier has an abnormality by analyzing the line monitoring signal with.

[0005]

In recent years, wavelength-multiplexed optical submarine cable networks have been rapidly developed. In this wavelength multiplexing optical submarine cable network, one or a plurality of add / drop devices are connected to a transmission line connecting transmission terminal devices, and optical signals having a predetermined wavelength are added / dropped by the add / drop devices. By doing
Communication is possible between a large number of transmission terminal devices.
With the development of the wavelength-multiplexed optical submarine cable network having such a configuration, it is also necessary to develop a monitoring device for the wavelength-multiplexed optical submarine cable network line. However, the above-mentioned conventional line monitoring system is for monitoring the line between two transmission terminal devices, and is for monitoring the wavelength-multiplexed optical submarine cable network line that is complicatedly branched by the optical submarine branching device. There was a problem that I could not do it.

An object of the present invention is to eliminate the above-mentioned problems of the conventional device and to provide a line monitoring device capable of monitoring a wavelength-multiplexed optical submarine cable network line.

[0007]

In order to achieve the above object, the present invention provides a plurality of transmission terminal equipments, an optical submarine repeater incorporating an optical loopback circuit, an optical submarine cable, and a specific wavelength. In a line monitoring device of a wavelength division multiplexing optical submarine cable network including an optical submarine branching device that adds / drops, a command to output a line monitoring signal to all of a plurality of transmitters provided in the transmission terminal equipment. Means for receiving, and a line monitoring signal output by the transmitter from the signal that has been fed back to be monitored through the optical loopback circuit built in the optical submarine repeater. And a means for detecting a fault in the line between the transmission terminal equipments based on the extracted signal.

According to the present invention, the line monitoring signal is output to all of the plurality of transmitters provided in the transmission terminal equipment, and the line monitoring signal is fed back via the optical loopback circuit built in the optical submarine repeater. Since the received signal is extracted, it is possible to monitor the normality and abnormality of each line even in a complicatedly branched WDM optical submarine cable network.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a system diagram showing the configuration of an embodiment of the present invention. In the figure, 1a and 1b are the transmitting side of the A station, the receiving side terminal device is 2a and 2b are the transmitting side of the B station, and receiving side terminal devices are 3a and 3b are the transmitting side and the receiving side of the D station, respectively. Terminal device, and 4a, 4
Reference numerals b are terminal devices on the transmitting side and the receiving side of station C, respectively. Each transmitting-side receiving terminal station includes a plurality of optical transmitters for transmitting optical signals of wavelengths λ1 to λn and a plurality of optical receivers for receiving optical signals of wavelengths λ1 to λn.

Reference numerals 5, 6, 7, and 8 are optical repeaters inserted in the repeater line. Each of the optical repeaters 5, 6, 7 and 8 is provided with an optical amplifier and a folded line on the upstream and downstream lines. Reference numerals 9 and 10 denote optical undersea branching devices that add / drop optical signals of specific wavelengths. Further, 11 is a line monitoring device provided in the A station, 23 is an optical coupler,
Reference numeral 24a is an optical reception signal from the first fiber pair, and 24n is an optical reception signal from the nth fiber pair. Further, 25a is an electric transmission signal to the first fiber pair, and 25n is an electric transmission signal to the nth fiber pair. Each of the stations B to D is also provided with a line monitoring device similar to the line monitoring device 11, but is not shown. Further, although only one fiber pair connecting between the transmission terminal equipments is shown in the drawing, usually, a plurality of fiber pairs are housed and laid in the same cable, and the line monitoring device 11 is provided with the plurality of fiber pairs. It is also configured to be able to monitor railroad tracks.

The line monitoring device 11, which is the main part of this embodiment, selects the fiber pair and outputs the optical reception signal from the selected fiber pair, and the selected optical reception signal. The optical amplifier 13 for amplifying the wavelength-multiplexed optical signal amplified by the optical amplifier 13 has wavelengths λ1 to
Array waveguide grating type filter 14 branched to λn and optical selector 1 for selecting one of the branched wavelengths λ1 to λn
5, a light receiving unit 16 for converting an optical signal of the wavelength selected by the optical selector 15 into an electric signal, a demodulating unit 17 for demodulating a received signal, and a correlating unit 18 for correlating the transmitting signal and the receiving signal. A control interface 19, a control device 20, a modulator 21 for modulating a transmission signal, and a selector 22 for selectively transmitting the modulation signal to the optical transmitter of each station. The correlator 18 correlates the transmission signal and the reception signal to determine whether the reception signal is normal or abnormal.

Next, the operation of this embodiment will be described. First, the optical selectors 12 and 15 are controlled so that the line supervisory signal output from the optical transmitter of the terminal device on the transmission side selected by the selector 22 is selected by the optical selectors 12 and 15. Now, assuming that the selector 22 selects the optical transmitter 1a1 having the wavelength λ1 of the transmission side terminal device of the station A,
The optical transmitter 1a1 outputs a signal in which the line monitoring signal output from the modulator 21 is superimposed on the optical signal for communication. As shown in the figure, assuming that the optical signal of wavelength λ1 is used for communication with the station B, the optical signal output from the optical transmitter 1a1 and the line supervisory signal are inserted in the relay line. Optical repeater 5, optical undersea branching device 9 and optical repeater 6
Is transmitted to the receiving side terminal device 2b of the B station. In addition,
Although only two optical repeaters are shown in the figure, the number of optical repeaters is not limited to this. Each optical repeater has an optical amplifier and a line for returning the optical signal amplified by the optical amplifier.

Therefore, the optical signal and the line supervisory signal output from the optical transmitter 1a1 of the A station are amplified by each relay station, and reach the receiving side terminal station device 2b of the B station through the optical subsea branching device 9. , A part of it is returned by the return line of each relay station and is returned to the receiving side terminal device 1b of the A station. The returned optical signal and part of the line monitoring signal are taken out by the optical coupler 23 and sent to the line monitoring device 11. The optical selector 12 of the line monitoring device 11 selects the signal from the A station, and the selected signal is amplified by the optical amplifier 13. Then, the arrayed-waveguide grating filter 14 divides the wavelengths into individual wavelengths λ1 to λn, and the optical selector 15 uses the wavelength λ1
Select the wavelength λ1 in ~ λn. Selected wavelength λ1
Signal is converted into an electric signal by the light receiving unit 16 and input to the demodulation unit 17. The signal demodulated by the demodulation unit 17 is compared with the transmission signal by the correlation unit 18 to determine whether the feedback signal is normal or abnormal. As a result, the line monitoring device 11
It becomes possible to monitor whether or not there is a failure in the relay line between the station and the B station. If the optical amplifier of a certain repeater station inserted in the repeater line between the A station and the B station fails or the repeater line itself fails, the control unit 20 determines that a feedback signal with weak power is generated. By detecting whether it is from the second relay station, it is possible to estimate or identify the location where the failure or the failure has occurred.

Although the above description is for line monitoring between the A station and the B station, line monitoring between the A station and the D station, and between the A station and the C station can be similarly performed. Specifically, station A and D
Since the stations communicate using optical signals of wavelength λ2,
First, the line monitoring device 11 uses an optical selector so that the line monitoring signal is output from the optical transmitter of wavelength λ2 of station A and the feedback signal from the optical transmitter of wavelength λ2 can be compared with the transmission signal in the correlator 18. 12, 15 and the selector 22 are controlled. Then, the correlation unit 18 and the control unit 20 monitor from the input feedback signal whether or not a failure has occurred in the relay line connecting the A station and the D station. Also in monitoring the relay line between the A station and the C station, the line monitoring device 11 outputs a line monitoring signal from the optical transmitter of the wavelength λn of the A station, and the feedback signal from the optical transmitter of the λn is received by the correlator 18. The optical selectors 12 and 15 and the selector 22 so that they can be compared with the transmission signal at
It becomes possible to monitor the failure of the relay line in the same manner as described above by controlling the.

Next, the line monitoring device 11 includes the first to the first stations of the A station.
Control is performed so that the line supervisory signals are sequentially transmitted from each transmitter of the transmission side terminal equipment of n fiber pairs, and each feedback signal is received in synchronization with this to detect normality or abnormality of each feedback signal. By doing so, it is possible to detect a failure in all the relay lines with which station A is communicating. Also,
By cyclically performing this operation, it is possible to constantly monitor the failure of the relay line related to the A station, and to provide a highly reliable wavelength-multiplexed optical submarine cable network. The above explanation was for monitoring the relay line between the A and B stations, between the A and D stations, and between the A and C stations.
It is apparent that the line monitoring between the D stations, the B-C stations, and the D-C stations can be performed by the line monitoring device installed in each of the B, D, and C stations by the same operation as described above. Ah

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 shows only the main part of the present embodiment, and other configurations are the same as or equivalent to those in FIG. 1, so the illustration is omitted. The feature of this embodiment is that an optical coupler is provided at each of the signal input sides of the respective receivers of the receiving side terminal device 1b of the A station, and the wavelengths λ1 to λn output from the respective transmitters of the A station by the optical coupler. This is a point in which a part of the feedback signal of (1) is extracted and a part of the feedback signal of the wavelengths λ1 to λn is input to the line monitoring device 30. The configuration of the line monitoring device 30 can be simplified as compared with that of the first embodiment, and the optical selector 31, the light receiving unit 32, and the measurement / control unit 3 are provided.
3 and a selector 34. Here, the measurement / control unit 33 includes the demodulation unit 17 and the correlation unit 1 of FIG.
8, the control interface 19, the control device 20, and the modulator 21 have the same configuration and function.
Reference numeral 35a is an optical reception signal from the first fiber pair, and 35n is an optical reception signal from the nth fiber pair. 36a is an electrical transmission signal to the first fiber pair, and 36n is an electrical transmission signal to the nth fiber pair.

The optical selector 31 inputs not only the feedback signal from the first fiber pair of station A, but also the feedback signals from other fiber pairs. The optical selector 31 arbitrarily selects one of the feedback signals according to the signal from the measurement / control unit 33. The optical signal selected by the optical selector 31 is converted into an electric signal by the light receiving unit 32 and input to the measurement / control unit 33. The measurement / control unit 33 checks whether or not the feedback signal has a predetermined power, normal if the power is the predetermined power, and if there is a feedback signal that is not the predetermined power, the optical repeater corresponding to the feedback signal. It is estimated or determined that an abnormality has occurred in the repeater section adjacent to the repeater or optical repeater.
The selector 34 selects a transmitter that sends out the modulated supervisory signal and superimposes it on the optical signal according to a command from the measurement / control unit 33. The selected transmitter superimposes the supervisory signal on the optical signal and transmits it. According to this embodiment, the wavelength-multiplexed optical submarine cable network line can be monitored as in the first embodiment, and the configuration of the line monitoring device can be simplified. The array waveguide grating type filter may be a narrow band wavelength filter applying an optical demultiplexer such as a 3 dB coupler and a dielectric multilayer film type or an optical fiber grating. Further, in the present embodiment, a plurality of fiber pairs wavelength-multiplexed by one line monitoring device are targeted for monitoring, but a line monitoring device may be provided for each fiber pair.

[0018]

As is apparent from the above description, according to the present invention, conventionally, only one fiber pair and one wavelength of the optical submarine cable network line can be monitored, whereas one fiber pair is wavelength-multiplexed. An effect that it is possible to monitor a line for transmitting an optical signal, in other words, an optical submarine cable network line between a plurality of transmission terminal station devices connected via an optical submarine branching device that adds / drops a specific wavelength There is. Further, according to the inventions of claims 2 and 3, there is an effect that the line monitoring of a plurality of fiber pairs can be performed by one line monitoring device.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a block diagram showing a main part of a configuration of a second exemplary embodiment of the present invention.

FIG. 3 is a block diagram for explaining a conventional line monitoring method.

[Explanation of symbols]

1a, 2a, 3a, 4a ... Transmitting side terminal device 1b, 2
b, 3b, 4b ... Receiving side terminal device, 5, 6, 7, 8 ... Optical repeater, 9, 10 ... Optical undersea branching device, 11 ... Line monitoring device, 12 ... Optical selector, 13 ... Optical amplifier, 14 Array array grating filter, 15 Optical selector, 16 Photoreceptor, 17 Demodulator, 18 Correlator, 19 Control interface, 20 Control device, 21 Modulator, 22 Selector, 23 Optical Coupler, 30 ... Line monitoring device, 31 ... Optical selector, 32 ... Light receiving part, 33 ... Measurement control part, 34 ... Selector.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Naoki Norimatsu 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo International Telegraph and Telephone Corporation (72) Eiichi Shibano 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo No. International Telegraph and Telephone Corporation (72) Inventor Yukio Horiuchi 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo Within International Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. A wavelength division multiplexer comprising a plurality of transmission terminal devices, an optical submarine repeater incorporating an optical loopback circuit, an optical submarine branching device for adding / dropping a specific wavelength, and an optical submarine cable connecting these devices. In a line monitoring device for an optical submarine cable network, means for instructing all of a plurality of transmitters provided in the transmission terminal device to individually output a line monitoring signal, and the optical submarine repeater Means for receiving a signal fed back from a line to be monitored through an optical loopback circuit built in, and extracting a line monitoring signal output by the transmitter from the signal; And a means for detecting a fault in the line between the transmission terminal equipments according to the received signal. 2. The line monitoring apparatus for a wavelength-division multiplexed submarine cable network according to claim 1, wherein a part of the feedback signal extracted from each fiber pair is analyzed for each wavelength, and A line monitoring device for a wavelength division multiplexing optical submarine cable network characterized by detecting a fault. 3. The line monitoring apparatus for a wavelength-division multiplexed submarine cable network according to claim 1, wherein the feedback signal of each fiber pair is divided for each wavelength, and a part of the divided wavelengths is analyzed for each transmission terminal station. A line monitoring device for a wavelength division multiplexing optical submarine cable network, characterized in that a line fault between the devices is detected.