JP3949503B2 - Optical amplifier and optical communication system using the amplifier - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes an automatic current control (hereinafter referred to as “ACC”) circuit and an automatic output level control (hereinafter referred to as “ALC”) circuit or an automatic gain control (hereinafter referred to as “AGC”) circuit. The present invention relates to an optical amplifier that outputs and controls the output power of light to a predetermined level later, and an optical communication system using the amplifier.
[0002]
[Prior art]
In the conventional optical communication system, the use of laser light has become mainstream as the transmission distance becomes longer and the transmission capacity increases. In this optical communication system, an optical signal output by modulation of laser light is propagated using an optical fiber. FIG. 8 is a block diagram showing a configuration of a conventional example of this optical communication system, in which the communication station 10 and the communication station 20 are connected by the downstream and upstream optical fibers 1 and 2, and the optical fibers 1 and 2 are transmitted. Some optical signals are amplified by optical amplifiers (OFAs) 11, 12 and 21, 22 to perform bidirectional optical transmission between communication stations.
[0003]
A communication station 10 that constructs this optical communication system includes a B-OFA 11 and a P-OFA 12 connected to the downstream and upstream optical fibers 1 and 2, and a WDM (optical division) connected to the input end of the B-OFA 11. Multiplex apparatus), an optical multiplexer 13 connected to the output end of the P-OFA 12, and an optical transmitter 15a for transmitting an optical signal to the optical multiplexer 13 for each wavelength, for example. To 15d, a plurality of optical receivers 16a to 16d that receive the optical signals demultiplexed for each wavelength by the optical demultiplexer 14, and a monitoring module (SV) for monitoring the optical fibers 1 and 2 and the devices in the station ) 17.
[0004]
The communication station 20 includes P-OFA 21 and B-OFA 22 connected to the downstream and upstream optical fibers 1 and 2, and a WDM optical demultiplexer 23 connected to the output end of the P-OFA 21, for example. For example, a WDM optical multiplexer 24 connected to the input end of the B-OFA 22, and a plurality of optical receivers 25 a to 25 d that receive optical signals demultiplexed by wavelength, for example, by the optical demultiplexer 23, The optical multiplexer 23 includes, for example, optical transmitters 26a to 26d that transmit optical signals for each wavelength, and an SV 27 that monitors the optical fibers 1 and 2 and the devices in the station.
[0005]
In such an optical communication system, the power of laser light is very strong due to demands of customers, etc., and the light output after being amplified by the OFAs 11, 12, 21, 22 has very high light intensity. It is getting stronger. For this reason, it is dangerous if the laser beam enters the eyes of a human body, especially an operator. For example, the optical fiber is cut by some obstacle, and the operator is exposed to the laser beam emitted from the end face of the cut fiber. The fear of doing was increasing. Thus, in order to operate the optical communication system safely and accurately, it is necessary to consider the safety of the human body.
[0006]
In this communication system, as shown in FIG. 8, for example, when a break occurs in the optical fiber 2, the disconnection of the optical fiber 2 is detected, and for safety reasons, an automatic laser shutdown (ALS) function is provided. The light output was forcibly stopped by working.
[0007]
In this optical communication system, the automatic restart control (ARC) function works when the optical fiber breakage is repaired by maintenance and the optical fiber is restored to a state where optical signal communication is possible. Thus, light is automatically output from the OFA to amplify the optical signal so that optical communication is possible.
[0008]
That is, the communication recovery operation on the communication station 10 side when the optical fiber 2 is disconnected will be described based on the flowchart of FIG. 9. When the SV 17 detects the disconnection of the optical fiber 2 (step 101), the OFS 11, 12 is shut down for safety reasons (step 102).
[0009]
Next, as shown in the configuration diagram of FIG. 10, when the disconnection 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 and transmission is automatically performed. And control so that the optical signal can be communicated (step 103).
[0010]
In this ARC function, a first optical pulse having a predetermined pulse width and a predetermined optical output power (hereinafter referred to as “first restart pulse”) is transmitted from, for example, the transmitter 15 d of the communication station 10 via the B-OFA 11. The In the communication station 20, when the first restart pulse is received by, for example, the receiver 25d, the SV 27 detects this, and toward the communication station 10 to which the first restart pulse has been sent, for example, A second optical pulse having a predetermined pulse width and a predetermined optical output power (hereinafter referred to as “second restart pulse”) is transmitted from the transmitter 26d via the B-OFA 22.
[0011]
In the communication station 10, when the second restart pulse is received by the receiver 16d, for example, the SV 17 recognizes this (step 104). However, in the recognition operation of the SV 17, the optical fiber 2 is normal 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 it has recovered. If the second restart pulse returned during transmission of the first restart pulse cannot be received by the receiver 16d, it is determined that communication is impossible, the output operation of the OFAs 11 and 12 is stopped, and the step again Returning to 103, the restoration of the optical fiber 2 is confirmed.
[0012]
Here, when it is confirmed that the optical fiber 2 has been normally restored, the SV 17 switches from the pulse output to the communicable optical output power (continuous output) to perform optical output, and is connected to the other. If there is a communication station, the optical output of the station is restarted to perform normal operation of the system (step 105).
[0013]
However, in the above conventional example, there is a possibility that the output power of the optical pulse exceeds the safety standard from the disconnected portion of the optical fiber. Therefore, in the safety standard of IEC: 60825-1 (2000 version), for example, when the wavelength used for the optical communication system is 1.55 μm band, the optical level is 10 dBm or less, which is called class 1 and is called when a failure occurs. Although a safety function such as a shutdown function for temporarily stopping the optical output is not stipulated, this light level of 17 dBm or less is called class 3A, and the above safety function or the restart pulse of FIGS. 11 and 12 is used. As shown in the relationship between the pulse width and the optical power, a safety function for the human body is added.
[0014]
In order to satisfy this safety standard, in the above-mentioned conventional optical amplifier, the OFA is controlled by AGC or ALC to capture the restart pulse transmitted from the transmitter of one communication station, and this pulse is optically amplified. To the receiver of the other communication station. FIG. 13 is a block diagram showing an example of a conventional optical amplifier. Here, a case where the OFA 21 is controlled as a representative is shown. 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 optical couplers 30 and 31, respectively, and then detected by photodiodes (PD) 32 and 33. The gain of the OFA 21 is controlled by controlling the drive current of the pump laser diode (LD) 35 by the AGC circuit 34 so that the optical power ratio is always a desired value (gain).
[0015]
[Problems to be solved by the invention]
However, when the OFA is controlled by the AGC or ALC control circuit in the conventional optical amplifier, if the desired optical output power is output from the shutdown state at the time of failure, the desired optical output power is obtained. It takes a long time to output. 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 intermediate optical amplifier receives this pulse and amplifies its optical output power to receive the restart side. This is because if the rise of the optical output is slow, the pulse width decreases, and depending on the degree of the decrease in the pulse width, a state in which this pulse cannot be received by the receiver occurs.
[0016]
Therefore, if the time until the desired optical output power is output from the shutdown state becomes longer, the pulse width of the restart pulse must be increased. However, if this pulse spreads, the optical output power that can be output becomes lower due to the relationship between the pulse width of the restart pulse and the optical power safety standard, and the transmission distance of the restart pulse that transmits the optical fiber is reduced. There was a problem that the optical communication over a long distance could not be performed because of the limitation.
[0017]
The present invention has been made in view of the above problems, and an amplifier capable of rapidly rising from a shutdown state to an output of a desired optical power and enabling long-distance transmission of an optical signal, and optical communication using the amplifier The purpose is to provide a system.
[0018]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention has a pumping light source, optically amplifies the input optical signal by combining it with the light from the pumping light source, and outputs it at the time of restart after recovery from a fault. In the optical amplifier for controlling the output of the light to be emitted, the current control means for controlling the drive current of the excitation light source to be constant, the first detection means for detecting the optical power of the light input to the optical amplifier, and the light Second detection means for detecting the optical power of light output from the amplifier, and the first and second detection meansThe output level of light from the excitation light source is controlled based on the optical power detected in stepLevel control means, and at the time of restart,To be below the first optical power level specified from the safety standard relationship between the pulse width of the restart pulse and the optical powerCurrent control by the current control meansFixed timeAnd after a certain timeThe second optical power level is higher than the first optical power level.Control of light output level by the level control meansExecuteAnd an optical amplifier comprising a control execution means.
[0019]
According to the present invention, the current control means and the level control means are provided, and at the time of restart after recovery from a fault, the current control means is used to quickly control the drive current value of the light source to be constant, and after this restart, the constant time has elapsed. Later, the control method is switched, and the control of the light output level output from the pumping light source is executed using the level control means, so that the light output is quickly raised.
[0020]
According to a second aspect of the present invention, in the above invention, the level control means performs gain control on a signal intensity change of light from the excitation light source based on the first and second detection means, and the control The executing means executes the gain control by the level control means after the predetermined time.
[0021]
  According to the present invention, the current control means and the level control means for controlling the gain with respect to the change in the optical signal intensity are provided, and the state showing 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 figure, at the time of restart after recovery from the failure of the optical transmission line, first, in the region 1 (between T1 and T2), the optical output power of P1 is set up as a target. Since the light level of P1 is determined by the drive current value that flows to the excitation light source, the current value is set in advance. Next, in 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 and 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)), and then in region 4 (after T4), the control method is switched and the level control means switches from the excitation light source. The gain control is executed for the light of, and constant control of the light output power P2 is performed, so that the light output is quickly raised.The “optical output power P1” is an optical power level at the time of restart and corresponds to the first optical power level. The “optical output power P2” is an optical power level after a certain time from the restart, and corresponds to the second optical power level.
[0022]
According to a third aspect of the present invention, in the above invention, the level control means controls the light output level with respect to a change in input amplitude of light from the excitation light source based on the first and second detection means. And the control execution means controls the light output level by the level control means after the predetermined time.
[0023]
The present invention includes a current control means and a level control means for performing light output level control in response to a change in light input amplitude. After a certain time from the restart, the control method is switched, and the level control means The light output level is controlled in response to a change in the light input amplitude, and the light output is quickly raised.
[0024]
According to a fourth aspect of the present invention, the excitation light source outputs a light pulse of a predetermined level used for recovery from a failure by controlling the drive current in the current control means.
[0025]
According to the present invention, the control by the current control means is performed so that the optical pulse of the predetermined optical output power P1 that clears the safety standard is output with respect to the start of the optical output at the time of restart, and the rapid light Start up the output.
[0026]
According to claim 5 of the present invention, in the above invention, the excitation light source outputs light suitable for communication by gain control in the level control means.
[0027]
According to this invention, after the constant output control of the optical output power of the optical pulse by the current control means, the gain control by the level control means is performed to output the optical pulse of the desired optical output power P2 suitable for communication.
[0028]
According to claim 6 of the present invention, in the above invention, the excitation light source outputs light suitable for communication by output level control of the light in the level control means.
[0029]
According to the present invention, after the output control of the drive current of the excitation light source by the current control unit is controlled, the light output level is controlled by the level control unit, and light having a desired optical output power P2 suitable for communication is output.
[0030]
According to a seventh 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 that outputs a predetermined level of light upon the restart is provided. An optical communication system is provided.
[0031]
According to the present invention, the optical amplifier according to any one of claims 1 to 6 can be used to quickly obtain a desired optical power at the time of restart, so that the rise from the shutdown state to the output of the desired optical power can be performed quickly. Do.
[0032]
According to an 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 communication stations connected via an optical transmission line are provided. And providing a predetermined level of light from the optical amplifier upon restarting between the communication stations.
[0033]
According to the present invention, the optical amplifier according to any one of claims 1 to 6 is provided in a communication station that performs optical signal communication, and a desired optical power can be quickly obtained by using the optical amplifier in the communication station at the time of restart. Thus, the rising from the shutdown state to the output of the desired optical power is performed quickly.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary 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 denoted by the same reference numerals for convenience of explanation. The overall configuration of the optical communication system is substantially the same as that shown in FIGS.
[0035]
Example 1
FIG. 2 is a block diagram showing a configuration of the optical amplifier according to the first embodiment of the present invention. Here, the case where the OFA 21 is controlled is shown as a representative. In this figure, in this embodiment, in addition to the OFA 21, optical couplers 30 and 31, PDs 32 and 33, AGC circuit 34 and LD 35 similar to the conventional example of FIG. 8, an ACC circuit for controlling the level of optical output power from the OFA 21. 36 and a control execution unit 38.
[0036]
The ACC circuit 36 performs current control to flow a constant drive current to the pumping LD 35 so as to maintain the optical output power P1 that does not exceed the safety standard. In other words, the ACC circuit 36 controls the drive current of the pump LD 35 so that the OFA 21 sends out a restart pulse having an optical output power P1 with respect to the optical output from the transmitter. The general relationship between the drive current value flowing to the pumping LD and the optical output power of the pumping LD is the relationship shown in the current-optical output characteristic diagram of the pumping LD in FIG. 3, and the general threshold current is 10 to 100 mA. Thus, for example, the optical level of the optical output power is set to 100 mW at a drive current value of 400 mA.
[0037]
The AGC circuit 34 performs gain control of the OFA 21. That is, the optical input power and the optical output power of the OFA 21 provided on the optical fiber 1 are detected by the PDs 32 and 33 after being branched by the optical couplers 30 and 31, respectively, and the ratio of the detected optical powers. The AGC circuit 34 controls the drive current of the excitation LD 35 so that the gain always becomes a desired gain.
[0038]
The control execution unit 38 performs switching control between the ACC circuit 36 and the AGC circuit 34 in accordance with the level of optical output power from the OFA 21 detected by the PD 33. That is, the control execution unit 38 monitors the optical input / output power, and when detecting the restart pulse input after recovery from the optical fiber failure, controls the operation of the ACC circuit 36 to target the optical output power of the OFA 21. Is launched at P1. Further, the control execution unit 38 has a timer circuit (not shown) inside, and performs a constant control of the optical output power P1 for a certain period of time up to the time T3 shown in FIG. Then, the AGC circuit 34 is switched to raise the optical output power to the target P2.
[0039]
In addition, this control execution part 38 may be comprised by SV in a communication station, and may be comprised so that switching control may be performed with the control signal from SV. For example, when the control execution unit 38 is configured by SV, the optical input power detected by the PD 32 is monitored, and the shutdown operation is performed depending on the presence or absence of the optical input. In the following description, a case where the control execution unit 38 is configured by SV will be described.
[0040]
Next, the recovery operation of the optical communication of this optical amplifier will be described based on the flowchart of FIG. Here, as in FIG. 8, the recovery operation for the disconnection of the optical fiber 2 will be described. In the figure, the control execution unit 38 monitors the optical input power of the restart pulse detected by the PD 32 (step 201), recognizes the presence or absence of this optical input, and is in a normal state in which the optical fiber can perform optical communication. Is determined (step 202).
[0041]
Here, when this 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, adjacent communication stations (in this embodiment, the communication station 10 shown in FIG. 8). Since there is no response from the restart pulse, the optical amplifier 21 is shut down after the lapse of the region 5 (time T5) (step 203). In the recognition of this optical input, as in the conventional example, the communication state is determined by whether or not the restart pulse returned from the adjacent communication station can be received by the receiver during the transmission of the restart pulse from the own station. Deciding. In this shutdown state, after a certain period of time (time T6) has passed in the region 6, a restart pulse is sent again to the adjacent communication station in order to determine whether or not the optical fiber 2 has been restored.
[0042]
If 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 an initial current value to flow through the excitation LD 35. The initial current value is a current value for outputting the optical output power P1 from the OFA 21 so as not to exceed the optical output power of the optical pulse at the time of restart specified by the safety standard.
[0043]
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. Note that the light level of the optical output power P1 is determined by the value of the current flowing through the pumping LD 35. Therefore, for example, the initial current value is set in advance from the characteristic diagram shown in FIG. If the output power of the pump LD 35 can be confirmed, the optical output power of the OFA 21 is also determined.
[0044]
Next, in region 2 (T = T2 to T3), control by the ACC circuit is performed, and the initial current value passed through the excitation 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. Therefore, in this embodiment, the control time (T2 to T3) of the ACC circuit is set to 1 second or more, and the pulse width of the restart pulse (region 5) is set to 1 second in consideration of the rising characteristics of the transmitter and OFA output. When the pulse width of this restart pulse is 1 second, the optical output power of T2 to T3 is set to 12.55 dBm or less from the safety standards shown in FIGS.
[0045]
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 transmitted, the fact that the optical input is lost means that the light controlled by the ACC circuit 36 is not received by the receiving communication station, that is, It means that it is in a fault state. Therefore, if there is no optical input, the shutdown state is entered in step 203, and if there is an optical input, it is next determined whether or not time T> T0 (step 207).
[0046]
Here, T0 is a time obtained by adding the region 1 and the region 2, and here, it is determined whether or not the time T of the timer circuit has reached a certain time T3. If the timer time T has not yet reached the time T3, the process returns to step 205 to flow the initial current value. When the timer time T reaches a certain time T3, the control execution unit 38 ends the control of the drive current by the ACC circuit 36, switches the control to the AGC circuit 34, and detects the light input detected by the PDs 32 and 33. The power and optical output power are monitored, and gain control suitable for communication is performed (step 208).
[0047]
Then, the control execution unit 38 determines whether there is optical input power detected by the PD 32 (step 209). If there is optical input, the control execution unit 38 returns to step 208 to continue gain control by the AGC circuit 34, If there is no light input, it is determined that a failure has occurred, and a shutdown state is entered (step 203).
[0048]
Thus, in this embodiment, since the current control by the ACC circuit 36 is performed at the time of restart, it becomes unnecessary to monitor the optical output power. Therefore, the recognition time by the monitor monitoring becomes unnecessary, and the rise time of the optical amplifier 11 ( (T1-T2) can be shortened. By shortening the rise time, the pulse width of the restart pulse is also shortened, whereby the optical output power of the restart pulse can be increased, and it can be applied to longer-distance optical communications.
[0049]
(Example 2)
Next, another embodiment of the optical communication recovery operation in this optical amplifier will be described based on the flowchart of FIG. In this embodiment, when the SV and the control execution unit 38 are separately configured, the restart pulse is output by the optical amplifier by the control signal input from the SV in a state where the light from the transmitter is always output. The recovery operation at the time of failure is shown.
[0050]
That is, in this embodiment, since there is always light input, the timing for outputting the restart pulse cannot be determined by monitoring the presence or absence of light input as in the first embodiment. Therefore, in this embodiment, the operation is performed so that the output of the restart pulse is controlled by the control signal input from the SV. The state of the optical output power of the OFA 21 according to this embodiment is the same as the state diagram shown in FIGS.
[0051]
In FIG. 6, the control execution unit 38 is in the shutdown state of the optical amplifier 21 (step 301). In this shutdown state, after a certain time (time T6) in the region 6 has elapsed (see FIG. 5), the optical fiber 2 In order to determine whether or not has recovered, an initial current is passed through the excitation LD 35 (step 302). This initial current value is a current value for outputting the optical output power P1 from the OFA 21 as in the first embodiment.
[0052]
Next, the control execution unit 38 resets an internal timer circuit (not shown) and counts the first timer time Ta = 0 (step 303), and the optical output power of the OFA 35 is defined by the safety standard. The drive current is controlled by the ACC circuit 36 so as not to exceed the optical output power of the optical pulse at the time of restart (step 304), and a release signal from the SV is waited (step 305).
[0053]
Then, the presence / absence of a release signal from the SV is detected (step 306). When the release signal is input from the SV, the control of the drive current by the ACC circuit 36 is terminated, the control is switched to the AGC circuit 34, and the PD 32 , 33 to monitor the optical input power and optical output power, and perform gain control suitable for communication (step 307).
[0054]
Next, the control execution unit 38 determines whether or not a failure such as an optical fiber disconnection has occurred (step 308). If there is no failure, the control execution unit 38 returns to step 307 to continue gain control by the AGC circuit 34, If a failure has occurred, the process returns to step 301 to put the optical amplifier 21 into a shutdown state.
[0055]
If there is no release signal from SV in step 306, it is next determined whether or not the first timer time Ta> T0 (step 309). Here, T0 is the time obtained by adding the region 1 and the region 2 as in the first embodiment. Here, it is determined whether or not the time Ta of the timer circuit has reached a certain time T3. When the first timer time Ta has not yet reached T3, the process returns to step 302 to flow the initial current value. When the first timer time Ta reaches the predetermined time T3, the control execution unit 38 resets the timer circuit to perform the counting with the second timer time Tb = 0 (step 310), and the ACC circuit The control of the drive current by 36 is terminated, the supply of current to the pumping LD 35 is stopped by the control of the SV control signal, and the optical amplifier 21 is brought into a 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 operating time of the ACC circuit, and the second timer time Tb is for defining the time of the shutdown state.
[0056]
Here, T is the time of the region 6 shown in FIG. 5, and it is determined here whether or not the second timer time Tb has reached a certain time T6. If the timer time Tb has not reached T6 again, the process returns to step 311 to continue the control of the ACC circuit 36. When the timer time Tb reaches a certain time T6, the process returns to step 302 and the initial current value is supplied again to shift from the shutdown state to the restart state.
[0057]
In this way, in this embodiment, the restart pulse can be output by the ACC circuit 36 by the control signal from the SV. Therefore, even when there is always light input from the optical fiber, The rise time of the amplifier can be shortened, whereby the pulse width of the restart pulse can be shortened, the optical output power can be increased, and it can be applied to longer-distance optical communications.
[0058]
The present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, as shown in FIG. 7, an ALC circuit 37 is provided instead of the AGC circuit, and the drive current of the pump LD is output so that the optical level of the optical output power suitable for communication is output with respect to the optical output from the pump LD 35. It is also possible to control the light level to be constant.
[0059]
Also in this case, current control by the ACC circuit 36 is performed at the time of restart, and constant light level control by ALC is performed after this current control, so that the rise time of the optical amplifier is shortened and restarted as in the above-described embodiment. The pulse width of the pulse can be shortened and the optical output power can be increased, and an effect that it can be applied to longer-distance optical communication can be achieved.
[0060]
【The invention's effect】
As described above, according to the first aspect of the present invention, an excitation light source is provided, and an optical signal to be input is combined with the light from the excitation light source to be amplified and output, and after the failure recovery, An optical amplifier that performs output control of light input at the time of start-up includes a current control means and a level control means, performs current control by the current control means at the time of restart after recovery from a failure, and by a level control means after a certain time Since the level control is performed, the rising from the shutdown state to the output of the desired optical power is quickly performed, and the optical signal can be transmitted over a long distance.
[0061]
According to the second aspect of the present invention, the current control by the current control means is performed at the restart after recovery from the failure, and the gain control by the level control means is switched after a certain time. Therefore, from the shutdown state to the output of the desired optical power Rapid start-up enables long-distance transmission of optical signals.
[0062]
According to the third aspect of the present invention, the current control by the current control means is performed at the time of restart after recovery from the failure, and after a certain period of time, the control is switched to the control of the light output level with respect to the change in the light input amplitude by the level control means. To a desired optical power output quickly, enabling long-distance transmission of optical signals.
[0063]
In the fourth to sixth aspects of the present invention, the excitation light source outputs an optical pulse having a predetermined optical output power that clears the safety standard with respect to the rise of the optical output of the current control means at the time of restart, and the level. Since the light suitable for communication is output by the gain control by the control means or the optical output level control with respect to the change in the input amplitude of the light, the influence on the human body can be taken into consideration and the operation can be performed safely and accurately.
[0064]
According to the seventh aspect of the present invention, the optical communication system includes the optical amplifier according to any one of the first to sixth aspects so that a desired optical power can be obtained quickly, so that the rise from the shutdown state to the output of the desired optical power can be achieved. Can be done quickly.
[0065]
According to an eighth aspect of the present invention, the communication station connected to the optical transmission line includes the optical amplifier according to any one of the first to sixth aspects so that a desired optical power can be quickly obtained at the time of restart. It is possible to quickly start up to the output of optical power.
[Brief description of the drawings]
FIG. 1 is a state diagram showing a state of optical output power immediately after 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 characteristics of current and light output of the pumping LD shown in FIG. 2;
FIG. 4 is a flowchart for explaining an embodiment of an optical communication restoration operation in the optical amplifier shown in FIG. 2;
FIG. 5 is a state diagram showing a state of optical output power when an optical fiber is abnormal from a shutdown state.
6 is a flowchart for explaining another embodiment of the optical communication restoration operation in the optical amplifier shown in FIG. 2; FIG.
FIG. 7 is a configuration diagram showing a configuration of Embodiment 2 of an 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. 8;
FIG. 10 is a configuration diagram of an optical communication system used for explaining an ARC operation after failure recovery;
FIG. 11 is a diagram representing the relationship between the pulse width of the restart pulse and the optical power.
FIG. 12 is a diagram similarly 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-16d, 25a-25d Receiver
30, 31 Optical coupler
32, 33 PD
34 AGC circuit
35 Excited LD
36 ACC circuit
37 ALC circuit
38 Control execution part

Claims (8)

In an optical amplifier having a pumping light source, optically amplifying and outputting an input optical signal by combining with the light from the pumping light source, and controlling output of light input at the time of restart after failure recovery,
Current control means for controlling the drive current of the excitation light source to be constant;
First detection means for detecting the optical power of light input to the optical amplifier;
Second detection means for detecting the optical power of the light output from the optical amplifier;
Level control means for controlling an output level of light from the excitation light source based on the optical power detected by the first and second detection means;
At the time of the restart , the current control by the current control means is executed for a predetermined time so as to be equal to or lower than the first optical power level defined from the relationship of the safety standard between the pulse width of the restart pulse and the optical power. Control execution means for executing control of the optical output level by the level control means so that the second optical power level is higher than the first optical power level later;
An optical amplifier comprising:   The level control means performs gain control with respect to a change in signal intensity of light from the excitation light source based on the first and second detection means, and the control execution means includes the level control means after the predetermined time. The optical amplifier according to claim 1, wherein the gain control is executed by.   The level control means controls the light output level with respect to a change in the input amplitude of light from the excitation light source based on the first and second detection means, and the control execution means 2. The optical amplifier according to claim 1, wherein control of the optical output level by the level control means is executed.   4. The optical amplifier according to claim 1, wherein the excitation light source outputs a predetermined level of an optical pulse used for failure recovery by controlling a drive current in the current control unit. 5.   The optical amplifier according to claim 1, wherein the excitation light source outputs light suitable for communication by gain control in the level control means.   5. The optical amplifier according to claim 1, wherein the excitation light source outputs light suitable for communication by output level control of the light in the level control means. In an optical communication system for amplifying and transmitting an optical signal,
7. An optical communication system comprising the optical amplifier according to claim 1, wherein a predetermined level of light is output through an optical transmission line at the time of restart. In an optical communication system for transmitting an optical signal,
The optical amplifier according to claim 1, further comprising a plurality of communication stations connected via an optical transmission line, and having a predetermined level from the optical amplifier upon restarting between the communication stations An optical communication system characterized by outputting light.

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