JPH0730503A - Optical direct amplifier repeater - Google Patents

Abstract

PURPOSE:To discriminate an abnormal location in an optical transmission line and a repeater without interruption of a line by outputting an optical signal obtained by modulating a lighting means with a specific signal when deterioration in an optical input to the repeater is detected. CONSTITUTION:When an optical input signal is deteriorated due to any cause, an input side PD5 detects the decrease in the optical input via an input side optical branching device 1, it is informed to a monitor control circuit SV9. The SV9 controls an oscillator 10 based on the reduction in the optical input to allow a repeater to provide an output of an allocated frequency signal. Then the frequency signal modulates an oscillation output of a laser diode LD7 and the modulated optical output is given to an optical synthesizer 2 and an EDF 3 to send the signal from the repeater. Thus, a low pass filter or the like in a terminal station detects the frequency of the input signal and the reduction in the optical input in the repeater to which the frequency is allocated is recognized. Thus, which repeater is abnormal or whether or not an optical transmission line in front of the repeater is broken is discriminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a repeater arranged in an optical transmission line for amplifying an optical signal, and more particularly to an optical direct amplification repeater capable of monitoring an abnormality in the optical transmission line or the repeater.

[0002]

2. Description of the Related Art Generally, in an optical transmission system, FIG.
As shown in FIG. 2, a plurality of repeaters A1, A2, ... An are provided in bidirectional optical transmission lines F1 and F2 formed of optical fibers or the like connecting terminal stations A and B that transmit and receive optical signals. Particularly, in recent years, an optical direct amplification repeater for directly amplifying the power of an optical signal is provided, and is provided in each of the up line F1 and the down line F2 of the optical transmission line. In such an optical transmission system, as the optical input power in the repeater becomes smaller, the optical output power also becomes smaller. Therefore, by detecting this and increasing the amplification degree, the optical output power operates so as to return to the original value. .

However, for example, terminal station A to terminal station B
When an optical signal is transmitted to a repeater, if the repeater in the preceding stage of the repeater becomes abnormal, or if the optical transmission line in the preceding stage is broken, the optical input power of the repeater in one becomes small. , Only noise will be output from this repeater. Since no optical signal exists in the output noise, only the noise is output also in the next stage repeater.
Therefore, only noise is transmitted at the terminal station B to which the optical signal is to be transmitted, and at this time, there is a problem that which repeater is abnormal and which cable is disconnected cannot be identified.

For this reason, conventionally, there has been proposed a system in which a return path between an up line and a down line is provided in a repeater, and the optical transmission line is monitored by using this return path. For example,
FIG. 5 shows an example of a repeater equipped with the monitoring method. On the upstream line F1 of the optical transmission line, an input side optical branching device 1, an optical combiner 2 for combining pump light into an optical signal, and an erbium-doped fiber (hereinafter abbreviated as EDF) 3 for amplifying the optical signal 3
And an output side optical branching device 4 for branching the output signal.
Then, the optical output branched by the output side branching device 4 is detected by an output side photodiode (hereinafter abbreviated as PD) 6,
A laser diode (hereinafter, abbreviated as LD) 7 in which an automatic level controller (hereinafter, abbreviated as ALC, ALC: Auto Level Control) 8 generates excitation light by this detection output 7
The light output of is adjusted and the power of the light output is amplified to a constant level.

The optical input branched by the input side optical branching device is detected by the input side PD5, and the monitor control circuit (hereinafter abbreviated as SV) 9 controls the light emission of the LD7 based on the detected output. Therefore, the SV9 can detect the monitor signal superimposed on the optical signal via the input side PD5, and the SV9 can superimpose the monitor content of each part on the optical signal in the LD7 and output it. This configuration is the same in the down line F2, and the same reference numerals are assigned to each. And
The upstream and downstream SVs are connected to each other.

In the loopback monitoring system using such a repeater, a signal is transmitted from one terminal station after turning off the line of the transmission line consisting of an up line and a down line, and this signal is transmitted to a plurality of repeaters. Then, the signal is returned in order by, and control is performed to detect the returned signal at the terminal station. That is, when the signal from the upstream line F1 is input to one repeater, the input side PD5 detects this signal and outputs this signal to the upstream line S.
The signal is output from V9 to SV9 on the down line, and further, a signal is output through the down line F2. Therefore, when the signal from the up line F1 is not input to one repeater, the signal cannot be detected by the input side PD5, and this signal cannot be sent from the up line SV9 to the down line SV9.
It becomes impossible to output a signal through the down line F2. The fact that the signal cannot be output to the down line in this way is the same when there is an abnormality in the repeater itself.

Thus, for example, in the optical transmission system shown in FIG. 4, a signal is output from the terminal station A and a plurality of repeaters A are output.
1, A2, ..., An by detecting the optical signal in the down line of the terminal station A while performing the above-described control in sequence, the repeater is abnormal when the optical signal cannot be detected. Alternatively, it is possible to determine that the transmission path to the preceding repeater is broken. In addition, for the same purpose, FIG. 6 is a structure in which both of the upstream line and the downstream line are connected so that the optical output of the one line and the optical line of the other line are input. In this case, for example, when the signal is not input from the up line, the signal is not output from the repeater, so that the signal toward the down line is not output, and the monitoring can be performed in the same manner as described above. Another example of such a loopback monitoring method is disclosed in Japanese Patent Laid-Open No. 3-13018.

[0008]

In the loopback monitoring method in such a conventional optical direct amplification repeater, the line of the optical transmission line between the terminal stations in which the repeater is present is turned off, and the repeaters are sequentially arranged. If it is not operated, the abnormal portion cannot be discriminated. Therefore, there is a problem that it takes a long time to make the discrimination, and therefore the time during which the line is turned off becomes long. An object of the present invention is to provide an optical direct amplification repeater capable of discriminating an abnormal portion in an optical transmission line and a repeater without turning off the line.

[0009]

An optical direct amplification repeater of the present invention has a plurality of repeaters arranged in an optical transmission line, each of which is provided with a signal generator for generating a unique signal, and has its own repeater. When the optical input signal level to the optical signal is reduced, the optical signal modulated by each unique signal is output.
That is, each of the plurality of repeaters has a unit for amplifying an optical input, a unit for emitting pumping light for performing the amplification, a unit for detecting the optical input, and a signal unique to each repeater. And a means for modulating the light emitting means with this unique signal, and when it detects a decrease in the optical input to its own repeater, it modulates the light emitting means with the unique signal. The optical signal obtained by the above is output. Here, the signal generator that generates a unique signal is composed of an oscillator that generates a unique frequency for each of the plurality of repeaters, or a data generator that generates unique data for each of the plurality of repeaters.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention.
5 is a configuration of a repeater related to an upstream line F1 in the optical transmission system shown in FIG. It should be noted that although the same configuration is provided for the down line F2, the description thereof will be omitted. The upstream line F1 is provided with an input side optical branching device 1, an optical combining device 2 for combining pumping light into an optical signal, an EDF 3 for amplifying an optical signal, and an output side optical branching device 4 for branching an output signal. Further, an input side PD5 for detecting the power of the optical input branched by the input side optical branching device 1, an output side PD6 for detecting the power of the optical output branched by the output side branching device 4, and pumping light are generated. LD
7, an ALC 8 that controls the light emission output of the LD 7 by the detection output of the output side PD 6, and an SV 9 that controls the LD 7 by the detection output of the input side PD 5 and the like. Further, an oscillator 10 to which different frequencies are assigned to each of the plurality of repeaters is provided and is configured to oscillate under the control of the SV 9.

According to this structure, the optical signal received from the optical input passes through the input side optical branching device 1, the optical multiplexer 2, the EDF 3 and the output side optical branching device 4 and is sent out from the optical output. At this time, a part of the optical output branched by the output side optical branching device 4 is transferred to the PD 6
And the LD 7 is controlled by the ALC 8 to control the optical output power. Therefore, when the power of the optical input decreases, the power of the optical output also decreases. In response to this, the ALC 8 increases the output of the LD 7 and increases the gain of the EDF 3 to increase the power of the optical output. The output power can be kept constant. The monitor signal for monitoring this repeater is branched from the optical input superimposed on the optical signal by the input side optical branching device 1, detected by the PD 5, and input to the SV 9. The SV 9 modulates the LD 7 based on the monitor contents of each unit, superimposes it on the optical signal, and sends it as an optical output.

The operation when the optical input signal is lowered due to some factor will be described with reference to the waveform chart of FIG. The PD 5 detects a decrease in optical input via the input side optical branching device 1,
This is transmitted to SV9. The SV 9 controls the oscillator 10 based on this decrease in the optical input, and outputs the frequency signal (a in the figure) assigned to the repeater. Then, the oscillation output of the LD 7 (b in the same figure) is modulated by this frequency signal, and this modulated optical output (c in the same figure) is output to the optical combiner 2 and the EDF 3, and as a result, this optical output is sent from the repeater. To do. Then, the terminal station can obtain the signal shown in FIG. 9D by passing the transmitted signal through, for example, a low pass filter, and the frequency can be detected by measuring the period t from this signal. .

Therefore, the terminal station can recognize that the optical input is lowered in the repeater to which the frequency of the detected signal is assigned, and which repeater is abnormal or the optical transmission line in front of the repeater. It is possible to determine whether or not the wire has been disconnected. As a result, it is not necessary to turn off the transmission line for monitoring, and when an abnormality occurs in the repeater or the transmission line, the signal of the frequency assigned to each is output from the corresponding repeater, and the terminal station By detecting the frequency of this signal, it becomes possible to detect an abnormality, and the optical transmission line is never interrupted for monitoring. In addition,
If no optical signal is input, the optical output from the repeater is only noise, but at this time, a signal obtained by modulating the LD with the assigned frequency is output, and the repeater after the next stage amplifies and relays this signal. Therefore, the modulated signal is transmitted to the terminal station, and it is possible to detect it. Also in this case, the signal modulated at an appropriate level is transmitted by the action of the ALC provided in each repeater.

Here, instead of the oscillator 10, a data generator for generating the data of the code assigned to each repeater may be provided. That is, as shown in the waveform diagram of FIG.
When the input optical signal becomes small, each repeater outputs unique data (a in the figure) under the control of the SV9, and the data is used to modulate the output of the LD7 (b) in the figure, The optical output of the modulated signal (c in the same figure) is transmitted through the EDF 3 or the like. By passing the transmitted signal through a filter at the terminal station, the signal shown in FIG. 8D can be obtained, and by detecting the data from this, it is possible to determine which relay is abnormal. Further, in this case, the cause of the abnormality or the like can be recognized in the terminal station by outputting the cause of the abnormality or the like in the repeater or the optical transmission line as data. Although the above description is for the up line, it goes without saying that the same applies to the down line. Further, it goes without saying that the same can be applied to a unidirectional optical transmission system.

[0015]

As described above, according to the present invention, each of a plurality of repeaters arranged in the optical transmission line is provided with an oscillator for generating its own frequency, and the optical input signal level to its own repeater is high. When it is lowered, it is configured to output an optical signal modulated at its own frequency, so that the terminal station receives the optical signal and detects the frequency, so that any repeater fails. You can recognize if there is. Therefore, monitoring of a plurality of repeaters can be realized without turning off the line of the optical transmission line, and the optical transmission line is not interrupted for a long time. Further, each of the plurality of repeaters is equipped with a data generator that generates unique data, and when the optical input signal level to the repeater of its own is lowered, an optical signal modulated with the unique data is output. Thus, the abnormal repeater can be recognized in the terminal station without turning off the line. At this time, if the data includes the contents, it is possible to recognize the cause of the abnormality.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an embodiment of an optical direct amplification repeater of the present invention.

FIG. 2 is a waveform diagram of optical output at the time of abnormality in one embodiment of the present invention.

FIG. 3 is a waveform diagram of optical output at the time of abnormality in another embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical transmission system to which the present invention is applied.

FIG. 5 is a block diagram of an example of a conventional optical direct amplification repeater.

FIG. 6 is a block diagram of another example of a conventional optical direct amplification repeater.

[Explanation of symbols]

 1 input side optical branching device 2 optical multiplexer 3 EDF (erbium-doped fiber) 4 output side optical branching device 5 input side PD (photodiode) 6 output side PD (photodiode) 7 LD (laser diode) 8 ALC ( Automatic level controller) 9 SV (Supervisory control circuit) 10 Oscillator

Claims (4)

[Claims] 1. An optical transmission system in which a plurality of optical direct amplification repeaters are arranged in an optical transmission line extending between terminal stations, wherein the plurality of repeaters each generate a unique signal. And an optical direct amplification repeater configured to output an optical signal modulated by the unique signal when the optical input signal level to the repeater itself is lowered. 2. In an optical transmission system in which a plurality of optical direct amplification repeaters are arranged in an optical transmission line extending between terminal stations, each of the plurality of repeaters has means for amplifying an optical input. A means for emitting pumping light for performing this amplification; a means for detecting an optical input; a signal generator for generating a unique signal in each repeater; and a modulation for the light emitting means with the unique signal. And an optical signal obtained by modulating the light emitting means with the unique signal when detecting a decrease in optical input to its own repeater. Direct amplification repeater. 3. The optical direct amplification repeater according to claim 2, wherein the signal generator for generating a unique signal is an oscillator for generating a unique frequency for each of the plurality of repeaters. 4. The optical direct amplification repeater according to claim 2, wherein the signal generator for generating a unique signal is a data generator for generating unique data for each of the plurality of repeaters.