JP2003318837A - Optical amplifier and optical communication system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable long-distance transmission of an optical signal by promptly performing rise from a shutdown state to output of a desired optical power. <P>SOLUTION: At restart of an optical fiber after restoration of a failure, a driving current of excited LD (laser diode) is supplied by using an ACC (automatic current control) circuit and optical output is promptly raised by targeting an optical output power P1 in an area 1. Since the optical level of P1 is determined by the driving current to be supplied to the excited LD, its current value is preset. Next, constant control of the optical output power P1 is performed in an area 2, output of the excited LD is changed by targeting an optical output power P2 after fixed time T3 from the restart (an area 3 (between T3 and T4)), next, the ACC circuit is switched to the AGC (automatic gain control) circuit, the AGC circuit is made to execute gain control to a light from the excited LD, constant control of the optical output power P2 is performed, and the optical output is promptly raised. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic current control (hereinafter referred to as "ACC") circuit, an automatic output level control (hereinafter referred to as "ALC") circuit or an automatic gain control (hereinafter referred to as "AGC"). The present invention relates to an optical amplifier that has a circuit and controls the output power of light to a predetermined level after a failure recovery and outputs the same, and an optical communication system using the amplifier.

[0002]

2. Description of the Related Art In conventional optical communication systems, laser light has become the mainstream as the transmission distance becomes longer and the transmission capacity increases. In this optical communication system, an optical signal output by modulating laser light is propagated using an optical fiber. FIG. 8 is a configuration diagram showing a configuration of a conventional example of this optical communication system, in which a communication station 10 and a communication station 20 are connected by downlink and uplink optical fibers 1 and 2, and the optical fibers 1 and 2 are transmitted. Optical signal (OFA) 11,
There is one that amplifies by 12 and 21, 22 and performs bidirectional optical transmission between communication stations.

A communication station 10 that constructs this optical communication system.
Is B-O connected to the downstream and upstream optical fibers 1 and 2.
FA11 and P-OFA12, an optical multiplexer 13 of, for example, a WDM (optical division multiplexer) connected to the input end of the B-OFA11, and an optical demultiplexer of, for example, WDM connected to the output end of the P-OFA12. Unit 14 and optical transmitters 15a to 15 for transmitting optical signals to the optical multiplexer 13 for each wavelength, for example.
d, a plurality of optical receivers 16a to 16d for receiving the optical signals demultiplexed by the optical demultiplexer 14 for each wavelength, and a monitoring module (S) for monitoring the optical fibers 1 and 2 and devices in the station.
V) 17 and

Further, the communication station 20 includes a P-OFA21 and a B-OFA2 connected to the down and up optical fibers 1 and 2, respectively.
2, a WDM optical demultiplexer 23 connected to the output end of the P-OFA 21, a WDM optical multiplexer 24 connected to the input end of the B-OFA 22, and the optical demultiplexer 23. Then, for example, a plurality of optical receivers 25a to 25d for receiving optical signals demultiplexed for each wavelength and optical transmitters 26a to 26 for transmitting optical signals for each wavelength to the optical multiplexer 23.
d and the SV that monitors the optical fibers 1 and 2 and the equipment in the station
And 27.

In such an optical communication system, the power of the laser light has become very strong due to the demand of the customer, and the optical output after being amplified by the OFA 11, 12, 21, 22 is the optical intensity. Is becoming very strong. For this reason, it is dangerous if the laser light gets into the eyes of the human body, especially the worker. For example, the optical fiber is cut by some obstacle, and the worker is exposed to the laser light emitted from the end face of the cut fiber. The fear of doing so was increasing. As described above, in order to operate the optical communication system safely and appropriately, it is necessary to consider the safety of the human body.

In this communication system, as shown in FIG. 8, for example, when a disconnection occurs in the optical fiber 2, the disconnection of the optical fiber 2 is detected, and for safety reasons, an automatic laser shutdown (ALS) is used. ) The function was working to forcibly stop the optical output.

In this optical communication system, the broken optical fiber is repaired by maintenance, and when the optical fiber is restored to a state where optical signal communication is possible, automatic restart control (A
The (RC) function worked to automatically output light from the OFA to amplify the optical signal and enable optical communication.

That is, a communication recovery operation on the communication station 10 side when the optical fiber 2 is broken will be described with reference to the flowchart of FIG.
When the disconnection of (1) is detected (step 101), the system including the OFA 11 and 12 is shut down for safety reasons by the ALS function (step 102).

Next, as shown in the configuration diagram of FIG. 10, when the broken state of the optical fiber 2 is repaired and the optical fiber is restored to a state in which optical signal communication is possible, the ARC function is activated to automatically By operating the transmitter and OFA 11 and 12,
The optical signal is controlled so that it can communicate (step 10).
3).

In this ARC function, a first optical pulse (hereinafter, referred to as a "first restart pulse") having a predetermined pulse width and a predetermined optical output power is transmitted through the B-OFA 11 to the transmitter 15d of the communication station 10, for example. Sent from. Communication station 20
Then, the first restart pulse is transmitted to the receiver 25, for example.
When received at d, the SV 27 detects this and this first
The second optical pulse (hereinafter, referred to as “second restart pulse”) having a predetermined pulse width and a predetermined optical output power is transmitted from the transmitter 26d toward the communication station 10 to which the restart pulse B is transmitted. -Sent via OFA 22.

In the communication station 10, when the second restart pulse is received by the receiver 16d, the SV 17 recognizes it (step 104). However, this SV
In the recognition operation of 17, the optical fiber 2 is normally restored only when the second restart pulse received by the receiver 16d is received during the transmission of the first restart pulse by the transmitter 15d. Recognize that. Further, when the returning second restart pulse cannot be received by the receiver 16d during the transmission of the first restart pulse, it is determined that the communication is impossible, the output operation of the OFA 11, 12 is stopped, and the step is restarted. Returning to 103, the recovery confirmation of the optical fiber 2 is performed.

Here, when it is confirmed that the optical fiber 2 is normally restored, the SV 17 switches from the above pulse output to an optical output power (continuous output) capable of communication and performs optical output, and If there is a communication station connected to, the optical output of that station is also restarted and the system operates normally (step 105).

However, in the above-mentioned conventional example, there is a possibility that the output power of the optical pulse exceeds the safety standard and is output from the broken portion of the optical fiber. Therefore, IEC: 608
In the safety standard of 25-1 (2000 version), for example, when the wavelength used in the optical communication system is the 1.55 μm band, an optical level of 10 dBm or less is called class 1 and the optical output is temporarily output when a failure occurs. Although a safety function such as a shutdown function that stops automatically is not specified, this light level of 17 dBm or less is called Class 3A and the safety function described above and the pulse width and light of the restart pulse in FIGS. 11 and 12 are used. As shown in the relation of power, safety function for human body is added.

In order to satisfy this safety standard, in the optical amplifier of the above-mentioned conventional example, the restart pulse transmitted from the transmitter of one communication station is taken in by controlling the OFA by AGC or ALC, and this pulse is supplied. It is optically amplified and sent to the receiver of the other communication station. FIG. 13 is a block diagram showing an example of a conventional optical amplifier. Here, OFA is representatively shown.
21 shows the case of controlling 21. In this optical amplifier, the optical input power and the optical output power of the OFA 21 provided on the optical fiber 1 are branched by the optical couplers 30 and 31, respectively, and then detected by the photodiodes (PD) 32 and 33, which are detected. By controlling the drive current of the pump laser diode (LD) 35 by the AGC circuit 34 so that the ratio of the optical power is always a desired value (gain), the OF
Gain control of A21 is performed.

[0015]

However, in the above-mentioned conventional optical amplifier, when the OFA is controlled by the control circuit of the AGC or ALC, the desired optical output power is output from the shutdown state at the time of failure occurrence. Then, it takes a long time to output the desired optical output power. This is because when a restart pulse is transmitted from the transmitter of one communication station to the receiver of the other communication station, the optical amplifier on the way receives this pulse and amplifies its optical output power to However, if the optical output rises slowly, the pulse width will decrease, and depending on the degree of decrease in this pulse width,
This is because a state occurs in which this pulse cannot be received by the receiver.

Therefore, if the time from the shutdown state until the desired optical output power is output becomes long in this way, the pulse width of this restart pulse must be widened. However, if this pulse spreads, the optical output power that can be output will decrease due to the relationship between the pulse width of the restart pulse and the safety standard for optical power described above, and the transmission distance of the restart pulse transmitted through the optical fiber will decrease. There was a problem that the limitation could be made and the long distance optical communication could not be performed.

The present invention has been made in view of the above-mentioned problems, and uses an amplifier and a amplifier for quickly rising from the shutdown state to the output of desired optical power and enabling long-distance transmission of an optical signal. The present invention aims to provide a conventional optical communication system.

[0018]

In order to achieve the above object, the present invention has a pumping light source, and an optical signal to be input is multiplexed with light from the pumping light source to optically amplify and output the signal. In an optical amplifier that controls the output of light that is input at the time of restarting after failure recovery, current control means that controls the drive current of the pumping light source to be constant, and optical power of light that is input to the optical amplifier are detected. Based on the first detection means, the second detection means for detecting the optical power of the light output from the optical amplifier, and the first and second detection means, the communication from the excitation light source is performed. Level control means suitable for controlling the light output level, and the current control means for executing current control at the time of the restart, and after a certain period of time, the level control means controls the light output level. Optical amplifier is characterized in that a control execution means for causing is provided.

According to the present invention, the current control means and the level control means are provided, and at the time of restarting after the recovery from the failure, the current control means is used to quickly control the drive current value of the light source to a constant value, and this restarting is performed. After a certain time from, the control system is switched, and the level control means is used to control the optical output level output from the pumping light source, so that the optical output can be quickly raised.

According to a second aspect of the present invention, in the above invention, the level control means performs gain control with respect to a change in signal intensity of light from the pumping light source, based on the first and second detecting means. The control execution means executes the gain control by the level control means after the fixed time.

According to the present invention, the current control means and the level control means for controlling the gain with respect to the change of the optical signal intensity are provided, and the state of the optical output power immediately after the optical amplifier is started up from the shutdown state of FIG. As shown in the state diagram of FIG.
1 to T2), the optical output power of P1 is set as a target. The light level of P1 is determined by the value of the drive current passed through the excitation light source, so that current value is set in advance.
Next, in the region 2 (between T2 and T3), the current control means is used to quickly make the drive current value of the pumping light source constant to perform constant control of the optical output power P1, and after a certain time T3 from this restart, The output of the excitation light source is changed with the optical output power of P2 as a target (region 3 (between T3 and T4)),
Next, in the region 4 (T4 and thereafter), the control system is switched and the gain control is performed on the light from the pumping light source by the level control means to perform the constant control of the optical output power P2, and the rapid rise of the optical output. Plan.

According to a third aspect of the present invention, in the above invention, the level control means is based on the first and second detection means, and the optical output level with respect to a change in input amplitude of light from the excitation light source. The control execution means causes the level control means to control the optical output level after the fixed time.

According to the present invention, the current control means and the level control means for controlling the optical output level with respect to the change of the input amplitude of the light are provided, and after a certain period of time from the restart, the control system is switched and the level control means excites the light. The light output level is controlled with respect to the change in the input amplitude of the light from the light source, and the light output is quickly raised.

According to a fourth aspect of the present invention, the pumping light source outputs a light pulse of a predetermined level used for fault recovery by controlling the drive current in the current control means.

According to the present invention, with respect to the rise of the light output at the time of restart, the current control means controls so as to output the light pulse of the predetermined light output power P1 which clears the safety standard, Aim to start up the light output quickly.

According to a fifth aspect of the present invention, in the above invention, the pumping light source outputs light suitable for communication by gain control in the level control means.

According to the present invention, after the output control of the optical output power of the optical pulse by the current control means is controlled to be constant, the gain control is performed by the level control means to output the optical pulse of the desired optical output power P2 suitable for communication. .

According to a sixth aspect of the present invention, in the above invention, the excitation light source outputs the light suitable for communication by the output level control of the light in the level control means.

According to the present invention, after the output current of the excitation light source is controlled to be constant by the current control means, the optical output level is controlled by the level control means to output the light having the desired optical output power P2 suitable for communication. Let

According to a seventh aspect of the present invention, an optical communication system for transmitting an optical signal is provided with the optical amplifier according to at least one of the first to sixth aspects, which outputs a predetermined level of light at the time of the restart. An optical communication system is provided.

According to the present invention, the optical amplifier according to any one of claims 1 to 6 is used so that the desired optical power can be quickly obtained at the time of restarting, and the rising from the shutdown state to the output of the desired optical power. Do quickly.

According to a eighth aspect of the present invention, in an optical communication system for transmitting an optical signal, the optical amplifier according to at least one of the first to sixth aspects is provided, and a plurality of optical amplifiers connected via an optical transmission line are provided. There is provided an optical communication system including communication stations, wherein the optical amplifier outputs a predetermined level of light at the time of restart between the communication stations.

According to the present invention, a communication station for communicating an optical signal is provided with the optical amplifier according to any one of claims 1 to 6, and at the time of restart, the communication station uses the optical amplifier to quickly obtain a desired optical power. As obtained, the rise from the shutdown state to the output of the desired optical power is performed quickly.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an optical amplifier according to the present invention and an optical communication system using the amplifier will be described with reference to the accompanying drawings. In the following drawings, the same components as those in FIG. 13 are designated by the same reference numerals for convenience of description. The overall configuration of the optical communication system is almost the same as that shown in FIGS.

(Embodiment 1) FIG. 2 is a configuration diagram showing the configuration of Embodiment 1 of the optical amplifier according to the present invention. Note that here, a case where the OFA 21 is controlled is shown as a representative. In this figure, in this embodiment, the same OF as in the conventional example of FIG.
A21, optical couplers 30, 31, PDs 32, 33, AGC
In addition to the circuit 34 and the LD 35, the ACC circuit 36 that controls the level of the optical output power from the OFA 21 and the control execution unit 38 are included.

The ACC circuit 36 controls the current so that a constant drive current flows through the pump LD 35 so that the optical output power P1 that does not exceed the safety standard is maintained. That is, A
The CC circuit 36 controls the drive current of the pumping LD 35 so that the OFA 21 sends a restart pulse with an optical output power of P1 to the optical output from the transmitter.
The general relationship between the drive current value flowing to the pump LD and the optical output power of the pump LD is the relationship shown in the current-optical output characteristic diagram of the pump LD in FIG. 3, and the general threshold current is 10 to 1
At 00 mA, for example, the drive current value is 400 mA, and the optical level of the optical output power is set to 100 mW.

The AGC circuit 34 controls the gain of the OFA 21. That is, the O provided on the optical fiber 1
The optical input power and the optical output power of the FA 21 are detected by the PDs 32 and 33 after being branched by the optical couplers 30 and 31, respectively, so that the ratio of the detected optical powers is always the desired gain. The AGC circuit 34 is an excitation LD
The drive current of 35 is controlled.

The control execution unit 38 operates according to the level of the optical output power from the OFA 21 detected by the PD 33.
Switching control between the C circuit 36 and the AGC circuit 34 is performed. That is, the control execution unit 38 monitors the optical input / output power, and when detecting the restart pulse input after the recovery of the optical fiber failure, the control execution unit 38 controls the operation of the ACC circuit 36 to set the optical output power of the OFA 21 as a target. It is launched on P1. Further, the control execution unit 38 has a timer circuit (not shown) therein, and a constant control of the optical output power P1 for a fixed time until the time T3 shown in FIG. After that, the AGC circuit 34 is switched to raise the optical output power to the target P2.

The control execution unit 38 may be configured by the SV in the communication station, or may be configured to perform the switching control by the control signal from the SV. For example, when the control execution unit 38 is configured by SV, PD3
The optical input power detected in 2 is monitored, and the shutdown operation is performed depending on the presence or absence of this optical input. In the following description, the case where the control execution unit 38 is configured by SV will be described.

Next, the recovery operation of the optical communication of this optical amplifier will be described with reference to the flowchart of FIG. In addition,
Here, similarly to FIG. 8, the recovery operation for the disconnection of the optical fiber 2 will be described. In the figure, the control execution unit 38
The optical input power of the restart pulse detected by the PD 32 is monitored (step 201), the presence or absence of this optical input is recognized, and it is determined whether or not the optical fiber is in a normal state capable of optical communication. (Step 202).

If the optical input cannot be recognized, as shown in the state diagram of the optical output power when the optical fiber is abnormal in FIG. 5, the adjacent communication stations (in this embodiment, the communication shown in FIG. Since there is no restart pulse response from the station 10), the optical amplifier 21 is put into the shutdown state after the lapse of the region 5 (time T5) (step 203). Incidentally, in the recognition of this optical input, as in the case of the conventional example, the communication state is determined by whether or not the receiver can receive the restart pulse returned from the adjacent communication station during the transmission of the restart pulse from the own station. Deciding. In this shutdown state, after a certain period of time (time T6) in the area 6, the restart pulse is again sent to the adjacent communication station in order to determine whether or not the optical fiber 2 is restored.

When the optical input is recognized, the internal timer circuit is reset to set the timer time T = 0 (step 204). Then, the control execution unit 38 causes the excitation LD
An initial current value is passed through 35. The initial current value is a current value for causing the OFA 21 to output the optical output power P1 so as not to exceed the optical output power of the optical pulse at the time of restart defined by the safety standard.

In the region 1 (T = T1 to T2) shown in FIG. 1, the pumping LD 35 is activated with the optical output power P1 as a target to raise the optical output. The optical output power P
The light level of 1 is determined by the value of the current passed through the pumping LD 35, so the initial current value is set in advance from the characteristic diagram shown in FIG. 3, for example. If the output power of the pump LD 35 can be confirmed, the optical output power of the OFA 21 is also determined.

Next, in the area 2 (T = T2 to T3), A
The control by the CC circuit is performed, and the initial current value flowing in the exciting LD 35 is held (step 205). The time for holding this initial current value needs to be set longer than the optical pulse width for ARC control. So, in this example,
The control time (T2 to T3) of the ACC circuit is set to 1 second or more,
The pulse width (region 5) of the restart pulse is set to 1 second in consideration of the rising characteristics of the output of the transmitter or OFA, and when the pulse width of the restart pulse is 1 second, as shown in FIG.
According to the safety standards shown in FIG. 12, the optical output power of T2 to T3 is set to 12.55 dBm or less.

Next, the control execution unit 38 determines whether or not an optical pulse (restart pulse) is input (step 206). That is, in this region 2, since the restart pulse is being sent, the fact that there is no light input means that the light controlled by the ACC circuit 36 is not received by the communication station on the receiving side, that is, It means that they are in a disordered state. Therefore, if there is no light input, the shutdown state is entered in step 203,
If there is an optical input, then it is determined whether time T> T0 (step 207).

Here, T0 is the time obtained by adding the area 1 and the area 2, and here it is determined whether or not the time T of the timer circuit has reached the fixed time T3. This timer time T
Is not yet time T3, step 20
Returning to 5, the initial current value is passed. Also, this timer time T
Is reached for a certain time T3, the control execution unit 38 ends the control of the drive current by the ACC circuit 36 and controls the AGC.
By switching to the circuit 34, the optical input power and the optical output power detected by the PDs 32 and 33 are monitored, and gain control suitable for communication is performed (step 208).

Then, the control execution section 38 judges whether or not there is an optical input power detected by the PD 32 (step 209), and if there is an optical input, returns to step 208 to control the gain by the AGC circuit 34. If it is continued and there is no optical input, it is determined that a failure has occurred, and a shutdown state is entered (step 203).

As described above, in this embodiment, by controlling the current by the ACC circuit 36 at the time of restart, it is not necessary to monitor the optical output power, so that the recognition time by the monitor monitoring becomes unnecessary and the optical amplifier 11 of the optical amplifier 11 is not required. It is possible to shorten the rise time (between T1 and T2). This shortening of the rising time also shortens the pulse width of the restart pulse, which makes it possible to increase the optical output power of the restart pulse and to apply it to longer-distance optical communication.

(Embodiment 2) Next, another embodiment of the optical communication recovery operation in this optical amplifier will be described with reference to the flowchart of FIG. In this embodiment, when the SV and the control execution unit 38 are separately configured, a restart pulse is output by the optical amplifier in response to the control signal input from the SV when the light from the transmitter is constantly output. This shows the recovery operation when the operation is performed.

That is, in this embodiment, since the optical input is always present, the timing for outputting the restart pulse cannot be determined by monitoring the presence or absence of the optical input as in the first embodiment. Therefore, in this embodiment, the output of the restart pulse is controlled by the control signal input from the SV. The OFA 2 according to this embodiment is
The state of the optical output power of No. 1 is the same as the state diagrams shown in FIGS. 1 and 5.

In FIG. 6, the control execution unit 38 puts the optical amplifier 21 into the shutdown state (step 30).
1) In this shutdown state, after a certain period of time (time T6) in the region 6 (see FIG. 5), the optical fiber 2
In order to determine whether or not has been restored, an initial current is passed through the pump LD 35 (step 302). This initial current value is the same as that of the first embodiment.
It is a current value for outputting 1.

Next, the control execution unit 38 resets the internal timer circuit (not shown) to set the first timer time Ta = 0.
And count (step 303), and OFA35
Drive power is controlled by the ACC circuit 36 so that the optical output power of the optical pulse does not exceed the optical output power of the optical pulse at the time of restart defined in the safety standard (step 30
4) Then, the system waits for a release signal from the SV (step 305).

Then, the presence or absence of the release signal from the SV is detected (step 306), and when the release signal is input from the SV, the control of the drive current by the ACC circuit 36 is terminated, and the control is sent to the AGC circuit 34. Switch to PD 32,3
The optical input power and the optical output power detected in 3 are monitored, and gain control suitable for communication is performed (step 30).
7).

Next, the control execution unit 38 determines whether or not a failure such as an optical fiber disconnection has occurred (step 30).
8) If no failure occurs, the process returns to step 307 to continue the gain control by the AGC circuit 34. If a failure occurs, the process returns to step 301 to put the optical amplifier 21 into the shutdown state.

If there is no release signal from the SV at step 306, then the first timer time Ta>
It is determined whether it is T0 (step 309). Where T
Like the first embodiment, 0 is the time obtained by adding the area 1 and the area 2. Here, the time Ta of the timer circuit is the constant time T.
It is judged whether or not it has reached 3. If this first timer time Ta has not yet reached T3, step 3
Returning to 02, the initial current value is passed. Further, when the first timer time Ta reaches the fixed time T3, the control execution unit 38
Resets the timer circuit so that the second timer time Tb =
The count is set to 0 (step 310), the control of the drive current by the ACC circuit 36 is terminated, and the supply of the current to the pumping LD 35 is stopped by the control of the SV control signal, and the optical amplifier 21 is put into the shutdown state. (Step 311). Next, the control execution unit 38 determines whether or not the second timer time Tb> T (step 312). The first timer time Ta is for defining the operation time of the ACC circuit, and is the second timer time Tb.
Is for defining the shutdown time.

Here, T is the time of the area 6 shown in FIG. 5, and here the second timer time Tb is the constant time T6.
I am deciding whether or not I have reached. If the timer time Tb has not reached T6 again, the process returns to step 311 to continue the control termination of the ACC circuit 36. When the timer time Tb reaches the fixed time T6, step 30
After returning to 2, the initial current value is supplied again, and the shutdown state is changed to the restart state.

As described above, in this embodiment, since the restart pulse can be output by the ACC circuit 36 by the control signal from the SV, even when the optical input from the optical fiber is always present, the same as in the first embodiment. In addition, the rise time of the optical amplifier can be shortened, whereby the pulse width of the restart pulse can be shortened and the optical output power can be increased, and it can be applied to optical communication over a longer distance.

The present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention. For example, as shown in FIG.
An ALC circuit 37 is provided instead of the GC circuit, and the excitation LD
It is also possible to control the drive current of the pumping LD so as to perform constant control of the optical level so that the optical level of the optical output power suitable for communication is output with respect to the optical output from 35.

In this case also, the ACC circuit 3 is restarted.
6, the current control is performed, and the constant light level is controlled by the ALC after this current control. Therefore, the rise time of the optical amplifier is shortened, the pulse width of the restart pulse is shortened, and the optical output is reduced, as in the above-described embodiment. The power can be increased, and it can be applied to optical communication over a longer distance.

[0060]

As described above, according to the first aspect of the present invention, the pumping light source is provided, and the input optical signal is multiplexed with the light from the pumping light source to be optically amplified and output. An optical amplifier for controlling output of light input at restart after failure recovery is provided with a current control unit and a level control unit, and when restarting after failure recovery, current control is performed by the current control unit for a certain period of time. Since the level control is performed later by the level control means, the rise from the shutdown state to the output of the desired optical power can be performed quickly, and the optical signal can be transmitted over a long distance.

According to the second aspect of the present invention, at the time of restart after the failure recovery, the current control means performs the current control, and after a certain period of time, the level control means is switched to the gain control, so that the desired optical power is changed from the shutdown state. It enables quick rise to the output and enables long-distance optical signal transmission.

According to the third aspect of the present invention, the current control means controls the current at the time of restarting after the failure recovery, and after a certain period of time, the level control means switches to the control of the light output level with respect to the change of the light input amplitude. Rapidly rising from the shutdown state to the output of desired optical power and enabling long-distance transmission of optical signals.

In the fourth to sixth aspects of the present invention, the pumping light source outputs an optical pulse of a predetermined optical output power that clears the safety standard in response to the rise of the optical output of the current control means at the time of restart. At the same time, the light suitable for communication is outputted by the gain control by the level control means or the light output level control for the change of the input amplitude of the light, so that it is possible to operate safely and appropriately in consideration of the influence on the human body.

According to a seventh aspect of the present invention, the optical communication system is provided with the optical amplifiers of the first to sixth aspects so that a desired optical power can be quickly obtained. Therefore, from the shutdown state to the output of the desired optical power. Can be quickly started.

In the eighth aspect of the present invention, the communication station connected to the optical transmission line is provided with the optical amplifier of the first to sixth aspects so that a desired optical power can be quickly obtained at the restart.
It is possible to quickly rise from the shutdown state to the output of desired optical power.

[Brief description of drawings]

FIG. 1 is a state diagram showing a state of optical output power immediately after a startup of an optical amplifier from a shutdown state.

FIG. 2 is a configuration diagram showing a configuration of a first embodiment of an optical amplifier according to the present invention.

FIG. 3 is a characteristic diagram showing current and light output characteristics of the pumping LD shown in FIG.

4 is a flow chart for explaining an example of a recovery operation of optical communication in the optical amplifier shown in FIG.

FIG. 5 is a state diagram showing a state of optical output power when the optical fiber is abnormal from the shutdown state.

6 is a flow chart for explaining another embodiment of the recovery operation of optical communication in the optical amplifier shown in FIG.

FIG. 7 is a configuration diagram showing a configuration of a second embodiment of the optical amplifier according to the present invention.

FIG. 8 is a configuration diagram showing an overall configuration of an optical communication system.

9 is a flowchart for explaining an optical communication recovery operation of the communication station shown in FIG.

FIG. 10 is a configuration diagram of an optical communication system used for explaining the operation of the ARC after failure recovery.

FIG. 11 is a diagram showing a relationship between a pulse width of a restart pulse and optical power.

FIG. 12 is a diagram showing the relationship between the pulse width of the restart pulse and the optical power.

FIG. 13 is a configuration diagram showing an example of a configuration of a conventional optical amplifier.

[Explanation of symbols] 1, 2 optical fiber 10, 20 Communication station 11,12,21,22 Optical Amplifier (OFA) 13, 24 Optical multiplexer 14,23 Optical demultiplexer 15a-15d, 26a-26d transmitter 16a to 16d, 25a to 25d receiver 30,31 Optical coupler 32,33 PD 34 AGC circuit 35 Excitation LD 36 ACC circuit 37 ALC circuit 38 Control execution unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04B 10/17

Claims (8)

[Claims] 1. An excitation light source is provided, and an optical signal to be input is multiplexed with light from the excitation light source to optically amplify and output, and output control of light to be input at restart after failure recovery is performed. In the optical amplifier to be performed, current control means for controlling the drive current of the pumping light source to be constant, and first optical power detecting means for detecting the optical power of light input to the optical amplifier.
Suitable for communication with respect to the light from the excitation light source, based on the detection means, the second detection means for detecting the optical power of the light output from the optical amplifier, and the first and second detection means. Level control means for controlling the light output level, and control execution means for causing the current control means to perform current control at the time of the restart, and performing the light output level control by the level control means after a certain period of time. An optical amplifier comprising: 2. The level control means performs gain control on the signal intensity change of the light from the pumping light source based on the first and second detection means, and the control execution means sets the constant time. 2. The optical amplifier according to claim 1, wherein gain control by the level control means is executed later. 3. The level control means controls the light output level with respect to a change in the input amplitude of light from the pumping light source based on the first and second detection means, and the control execution means 2. The optical amplifier according to claim 1, wherein the optical output level is controlled by the level control means after the fixed time. 4. The pumping light source outputs a light pulse of a predetermined level used for fault recovery by controlling the drive current in the current control means.
[3] The optical amplifier according to any one of [3] to [3]. 5. The optical amplifier according to claim 1, wherein the pumping light source outputs light suitable for communication by gain control in the level control means. 6. The optical amplifier according to claim 1, wherein the pumping light source outputs light suitable for communication by controlling the output level of the light in the level control means. . 7. The optical amplifier according to claim 1, wherein in the optical communication system for amplifying and transmitting an optical signal, light of a predetermined level is output via an optical transmission line at the time of the restart. An optical communication system characterized by being provided. 8. An optical communication system for transmitting an optical signal, comprising the optical amplifier according to at least one of claims 1 to 6, and a plurality of communication stations connected via an optical transmission line, An optical communication system characterized in that the optical amplifier outputs a predetermined level of light between the communication stations upon restart.