JP2009200454A - Optical amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: while a high-speed optical amplifier with small transient response to burst signal input is required in accordance with expansion and complication of an application range of an optical network, waveform of input light can not be maintained since response speed is not sufficient in the conventional technology. <P>SOLUTION: The optical amplifier includes: a first input monitor means 550; a second input monitor means 560; an optical amplification means 310 including an optical amplification medium 300; an optical delay means 900; a control means 400 for performing feed-forward control; and a high-speed output variable means 610, when the optical amplification means is controlled by the feed-forward control according to signals of the input monitor means 500, response performance of the optical amplification medium is improved, and high-speed response performance is attained by utilizing an overshoot signal as a control signal. Furthermore, the high-speed and stable optical amplifier is attained by simultaneously performing high-speed feedback control of the high-speed output variable means 610 using signals of optical output monitors 700. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

    The present invention relates to an optical amplifier and an optical amplifier control method.

    In the Wavelength Division Multiplexing (WDM) communication network, rare earth doped fibers such as erbium-doped fiber amplifier (EDFA) that can amplify the wavelength band of several tens of nanometers as an optical signal are used. An optical amplifier is used.

    On the other hand, the form of an optical network has changed from a point-to-point network to a ring network using a Reconfigurable Optical Add-drop Multiplexer (ROADM) node. Furthermore, in recent years, the spread of optical networks to ordinary households has become full-scale.

    As the application range of the optical network expands and becomes complex in this way, the transmitted optical signal is required to be a burst signal.

    In bursty optical signal transmission, fluctuations in a wide dynamic range from signal OFF to ON are instantaneously repeated. In the case of 10 Gbit / sec, which is the current general signal transmission rate, fluctuations occur at the rise / fall of about 0.1 nsec, but the optical amplifier is also required to cope with such high-speed fluctuations.

    As a response to high-speed fluctuations in an optical amplifier using a rare earth-doped fiber, a method of delaying input to the rare earth-doped fiber by using a delay element as compared with monitoring of an input optical signal has been devised and described in Patent Document 1. .

In Patent Document 1, a method corresponding to high-speed input fluctuation is used by a feedforward control method of driving an excitation laser according to a result of monitoring an input signal. Furthermore, by delaying the input to the rare earth-doped fiber using a delay means, the time required for a series of controls such as monitoring of the input signal and driving of the excitation laser is secured, and the timing of fluctuation of the optical signal input to the rare earth-doped fiber is As a result of monitoring the input signal, fluctuations in the excitation laser beam controlled are substantially matched to reduce the control delay.
JP 2002-261364 A

Problems to be solved by the present invention

    When optical input signals with various fluctuation amounts are assumed, it is necessary to change the amount of energy to be injected in advance depending on the fluctuation amount of the optical input signal input to the optical amplifier using the rare earth doped fiber. However, since the method of Patent Document 1 is a fixed delay element, it is difficult to cope with various optical input fluctuations.

    In Patent Document 1, feedback control of the pump laser by monitoring the optical output signal is used for gain and output stabilization. However, since feedback control cannot be performed in a time of 1 μsec or less, high-speed stability is achieved. Conversion was difficult.

    In view of the above circumstances, it is a main object of the present invention to provide an optical amplifier whose gain and output are stably controlled in response to high-speed burst signal input having various fluctuation ranges.

Means for solving the problem

    In order to solve the above problems, the optical amplifier according to the present invention has a high speed and a variable width by controlling the amount of energy injected by the pump laser before the input optical signal that has changed at high speed is input to the rare earth doped fiber. This corresponds to the optical input signal.

    The optical amplifier according to claim 1 includes at least an input monitoring unit, an optical amplifying unit, an optical delay unit disposed in front of the optical amplifying unit, and an amplification of the optical amplifying unit using the input monitoring unit. An optical amplifier including control means for performing feedforward control for control, wherein an overshoot signal is used for the amplification control.

    Here, the “light amplification means” is amplification means that is excited by light or electrons and makes the output light intensity larger than the input light intensity, and includes an optical amplification medium. The “input monitoring means” means means for monitoring an electric signal or an optical signal including intensity information of light input to the optical amplifier in the previous period. “Feed forward control” means control for driving a controlled object by outputting a control signal to the controlled object in accordance with the magnitude of a signal that is also input to the controlled object. Further, the “overshoot signal” means a control signal that transiently shows a value larger than the steady level with respect to the steady level, as shown in FIG. Here, the steady level is the control signal intensity when one second or more has elapsed from the start of application of the control signal, and the transient means a time within 100 microseconds from the start of signal application. Further, the “optical delay means arranged in front of the optical amplifying means” means an optical delay means located on the input side of the optical amplifying means and at a position that does not give a delay to the input monitor means. .

    Further, the optical amplifier according to claim 2 includes signal branching means for branching the electrical signal output from the input monitor means, and electrical signal delaying means for delaying one of the branched electrical signals. The optical amplifier according to claim 1.

    In the optical amplifier according to claim 1 or 2, the control means preferably includes an overshoot generation circuit. Here, the “overshoot generation circuit” means an analog circuit or a digital circuit in general that generates the overshoot signal as an electric circuit.

    Specifically, the overshoot generation circuit is preferably a PID circuit. Here, as shown in FIG. 2, the “PID circuit” is a circuit in which the amount of control signal is determined by linear combination of three components of a proportional element, a differential element, and an integral element with respect to an input signal, and responds to the input signal. Any waveform can be generated.

    The optical amplifier according to claim 5 is the optical amplifier according to any one of claims 1 to 4, wherein the optical delay means is a variable optical delay means.

    6. The optical amplifier according to claim 6, wherein the overshoot generation circuit is driven by using a signal of the input monitor means. is there.

    7. The optical amplifier according to claim 7, wherein the variable optical delay means is driven using a signal of the input monitor means. is there.

    The optical amplifier according to claim 8 is the optical amplifier according to any one of claims 1 to 7, further comprising high-speed output variable means at a subsequent stage of the optical amplification medium. Here, the “high-speed output variable means” means a high-speed response performance that changes the output by outputting input light, giving a drive signal, and changing a 6 dB fluctuation within 10 microseconds before and after giving the drive signal. It means to have.

    9. The optical amplifier according to claim 9, further comprising output light monitoring means, and driving the high-speed output variable means by using a signal of the output light monitoring means. It is. Here, the “output light monitoring means” means means for detecting the power level of the output light using a part of the output light.

    The optical amplifier according to claim 10, wherein the high-speed output variable means is driven using a differential signal between a signal from the input monitor means and a signal from the output light monitor means. It is an optical amplifier of description. Here, the signal from the input monitor means is a signal including information on the input light intensity, and the signal from the output light monitor means is a signal including information on the output light intensity.

    The high-speed output variable means is preferably a high-speed variable optical attenuator from the viewpoint of a small amount of added noise and an economical viewpoint. Here, the “high-speed variable optical attenuator” is a high-speed variable-attenuator that attenuates and outputs input light, varies the amount of attenuation by providing a drive signal, and varies 6 dB in 10 microseconds or less before and after the drive signal is applied. It means a device with response performance.

    Furthermore, the high-speed variable optical attenuator preferably includes an electro-optic effect element, and the drive voltage of the high-speed variable optical attenuator is preferably 40 V or less from the viewpoint of ease of driving and high speed. Here, the “electro-optic effect element” means an element having an electro-optic effect such as Pockels effect or Kerr effect. Further, “the drive voltage is 40 V or less” means that the voltage difference applied to both ends of the electro-optic effect element is 40 V or less.

    The optical amplifier according to claim 13 is an optical amplifying unit, an optical delay unit disposed in front of the optical amplifying unit, a first input monitor unit disposed in front of the optical delay unit, and the optical delay. An optical amplifier comprising: second input monitoring means arranged at a subsequent stage of the means; and control means for performing feedforward control for amplification control of the optical amplification means using the first input monitoring means. An optical amplifier using an overshoot signal for the amplification control.

    The control means according to claim 13 preferably includes an overshoot generation circuit.

    Specifically, the overshoot generation circuit according to claim 13 is also preferably a PID circuit.

    The optical amplifier according to claim 16 is the optical amplifier according to any one of claims 13 to 15, wherein the optical delay means is a variable optical delay means.

    17. The optical amplifier according to claim 17, wherein the overshoot generation circuit is driven using a signal of the first input monitor means. It is an optical amplifier.

    18. The optical amplifier according to claim 18, wherein the variable optical delay means is driven using a signal of the first input monitor means. It is an optical amplifier.

    The optical amplifier according to claim 19, further comprising high-speed output variable means at a subsequent stage of the optical amplification medium.

    20. The optical amplifier according to claim 20, further comprising output light monitoring means, and driving the high-speed output variable means using a signal of the output light monitoring means. .

    21. The optical amplifier according to claim 21, wherein the high-speed output variable means is driven by a difference signal between a signal from the second input monitor means and a signal from the output light monitor means. The optical amplifier described.

    The high-speed output variable means is preferably a high-speed variable optical attenuator from the viewpoint of a small amount of added noise and an economical viewpoint.

    Furthermore, the high-speed variable optical attenuator preferably includes an electro-optic effect element, and the drive voltage of the high-speed variable optical attenuator is preferably 40 V or less from the viewpoint of ease of driving and high speed.

The invention's effect

    As described above, according to the present invention, it is possible to perform optical amplification in which gain and output are stably controlled in response to high-speed burst signal input having various fluctuation ranges.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings.

    A first embodiment is shown in FIG. The optical amplifier includes an input monitor unit 500, an optical amplification unit 310, a feedforward control unit 400, and an optical delay unit 900.

    The input monitoring means 500 is composed of a TAP type light receiving element 510 and a transimpedance type electric amplifier circuit (TIA) 520. Further, a part of the input light may be branched by an optical coupler and the level of the input light may be monitored. Furthermore, it is possible to input a part of the input light branched before the present optical amplifier to the input monitoring means (photodiode, TIA) of the optical amplifier.

    It is also possible to monitor the input light level by separating the monitor control light with a WDM coupler and passing the electrical signal equivalent to the input light level to the input monitor means by the monitor control light processing unit. It is. Furthermore, it is also possible to monitor the level of input light by passing to the input monitor means an electrical signal equivalently representing the input light level from the supervisory control light processing unit already processed in the previous stage of the optical amplifier. .

    The optical amplifying unit 310 uses an EDF as the optical amplifying medium 300, and includes a PUMP-LD 320 and a PUMP-LD drive circuit 330. Depending on the amplification factor (gain) to be set, PUMP-LD may be added so that pumping light is injected from behind the optical amplification medium 300. In addition to the EDF, the optical amplification means also includes a rare earth-doped fiber such as PDF (Placedmium Doped Fiber) or a semiconductor optical amplifier device.

    Regarding the control of the optical amplifying means 300, in order to drive the optical amplifying means 300 at a high speed in accordance with the level change of the input light, the PUMP-LD 320 is controlled by feed-forward using the input side TIA520 output information. At 403, the PUMP-LD 320 is driven using the control signal as an overshoot signal.

    In the differential operational amplifier 430 constituting this control means, the PUMP-LD can be driven with a desired drive current by setting the + side input, so that the gain can be set.

    The optical delay means 900 is composed of a single mode fiber of about 1 km and realizes a delay of about 5 μsec. As the optical delay means, an optical fiber that also serves to reduce or compensate for dispersion, such as a dispersion-shifted fiber or a dispersion compensation fiber, or a special fiber such as a polarization maintaining fiber, a holey fiber, or a photonic crystal fiber can be used. A multimode fiber can also be applied depending on the application. Furthermore, it is also possible to apply a variable delay device whose delay is variable by an electric signal.

    Next, speeding up by feedforward control using delay means and an overshoot signal will be described in detail.

    In FIG. 3, the optical signal monitored by the input monitoring means 500 is converted into an electric signal 30. The electric signal 30 is converted into the electric signal 40 by the feedforward control means 400 and is input to the PUMP-LD driving circuit 330 to drive the PUMP-LD 320. The PUMP light output from the PUMP-LD 320 by the signal input to the PUMP-LD 320 after the monitor signal is branched by the input monitoring unit 500 and then converted into the electrical signal, converted into the electrical signal 30 and the electrical signal 40. Is input to the optical amplifying medium 300, and it takes time until the response appears in the output light 20. The time required for this response varies depending on the wavelength of the PUMP-LD to be used and the optical amplification medium 300, but is generally several nsec to several tens of μsec.

    Without the delay means 900, the main component of the input optical signal is input to the optical amplification means 310 during the time required for the response, that is, until the PUMP light is changed in accordance with the fluctuation of the input light 10. Therefore, the gain of the optical amplifier becomes transiently too large or too small than the setting.

    Therefore, the delay unit 900 gives a delay equivalent to the time required for the response to the main component of the input optical signal, so that the PUMP light 50 that has passed through the feedforward control unit 400 prior to the fluctuation of the input optical signal is changed into the optical amplification medium. 300 can be entered.

    On the other hand, in the feedforward control, the power of the PUMP light 50 required is uniquely determined by the intensity of the input light. The total energy to be input prior to the main component of the signal is determined by the amount of fluctuation of the input light. The total energy is the product of the PUMP optical power and the injection time. As described above, the PUMP optical power is determined by the intensity of the input light. Therefore, if the fixed delay means is used, the total energy is controlled. You will not be able to.

    In the present invention, the power different from the steady state, that is, an overshoot signal, is transiently injected into the EDF, and the overshoot amount is controlled to follow various fluctuation amounts of the input light. When the variable light delay means is used, not only the overshoot amount but also the light delay time is controlled.

    FIG. 4 shows the principle that high-speed response characteristics can be obtained by driving an EDF using an overshoot signal in feedforward control.

    When the control signal from the control means is a square wave, the EDF has a slow response component inherent to the EFD, and therefore has a slow rise response. The drive signal level from the control means for obtaining the desired EDF response amplitude is set to level 1, and the drive signal level higher than that is set to 2. When driven at this level 2, as shown in FIG. 4, a large EDF response amplitude is obtained.

    When the control signal is overshooted to level 2 and then set to a waveform that settles to level 1, the EDF rises with a response corresponding to level 2 and then has a response amplitude corresponding to level 1. Therefore, it becomes possible to speed up the response of the EDF by overshoot.

    FIG. 5 shows the relationship between the overshoot amount and the delay amount. Since a quick response can obtain 100% of the required intensity, the required overshoot amount is larger as the delay amount is smaller, and is smaller as the delay amount is larger.

    In order to generate this overshoot amount, for example, as shown in FIG. 2, the control signal amount is obtained by linear combination of three components of a proportional element (P), a differential element (D), and an integral element (I) with respect to the input signal. There is a PID circuit to be determined, and an arbitrary waveform can be generated for an input signal.

    By adjusting the circuit constants of these three elements in a timely manner, a desired overshoot control signal is created, and the control signal of the optical amplifying means is used as an overshoot signal, thereby improving the slow response performance inherent to the optical amplifying means. It becomes possible.

    Furthermore, a digital method is also possible in which an overshoot waveform for an input is stored in a memory, an input monitor value is read, a necessary overshoot waveform is extracted from the memory, and converted into a control signal.

Next, conditions and experimental results (FIG. 6) in the configuration shown in FIG. 3 will be described. The applied EDF has an erbium concentration of 7.9 × 10 ²⁴ m ⁻³ and a length of 15 m.

    The wavelength of PUMP-LD was 0.98 μm and the maximum power was +23.5 dBm. The current for driving the PUMP-LD was a steady-state value of 370 mA and an overshoot current of 200%. The gain of the entire amplifier was set to 20 dB. The delay fiber was a 1 km single mode fiber, and the delay amount was about 5 μsec. The wavelength of PUMP-LD may be 1.48 μm, but in that case, at least the delay fiber can be shortened to 500 m or less.

    In the measurement, a light source having a wavelength of 1550 μm was used, and an input in which the light input increased stepwise to −4 dBm with respect to the reference level of −25 dBm. This is 21 dB as the input light amplitude fluctuation range.

    As can be seen from FIG. 6, it can be seen that a very high-speed response of 20 nsec or less is realized because the output is also substantially equivalent to the fluctuation of the high-speed input optical signal occurring at about 20 nsec.

    A second embodiment is shown in FIG. The optical amplifier includes first input monitoring means 550, second input monitoring means 560, optical amplification means 310, optical delay means 900, feedforward control means 400, high-speed output variable means 610, output light monitoring means 700, feedback control. Means 800 is used. The first input monitor unit 550, the second input monitor unit 560, and the output light monitor unit 700 include a TAP type light receiving element 510 and a transimpedance type electric amplifier circuit (TIA) 520. Further, a part of the signal light may be branched by an optical coupler and the level of the signal light may be monitored.

    Furthermore, it is possible to input a part of the input light branched before the present optical amplifier to the first input monitoring means (photodiode, TIA) of the optical amplifier. It is also possible to input an electric signal monitored before the present optical amplifier to the feedforward control means 400.

    The optical amplifying unit 310 includes an EDF, a PUMP-LD 320, and a PUMP-LD drive circuit 330 as the optical amplifying unit 300.

    The output light monitoring means 700 includes a TAP type light receiving element 510 and a transimpedance type electric amplifier circuit (TIA) 520.

    The high-speed output variable means 610 includes a high-speed variable optical attenuator (VOA) 620 and a VOA drive circuit 630. The high-speed output variable means may be a high-speed variable amplifier such as a semiconductor amplifier.

    The output signal of the first input monitor means 550 controls the feedforward control for controlling the PUMP-LD, and the signal monitored by the second input monitor means 560 controls the high-speed output variable means together with the output signal of the output light monitor means. It is used for feedback control.

    The second input monitor unit 560 is omitted, the electric signal 30 output from the first monitor unit 550 is branched into two, one to the comparison unit 410 and the other to the comparison unit via an electrical delay unit. 810 may be input. The electrical delay means in this case can be applied to a delay line that is a commercially available electronic component or a digital device that stores a signal in a memory and outputs the same signal after a delay of a desired time. .

    Next, with reference to FIG. 8, the principle of realizing high-speed response characteristics using high-speed output variable means will be described. By the high-speed output variable means, the slow response component of the EDF (the part enclosed by the square in the figure) is removed, and the response waveform is shaped into a square wave, so that only the component with the fast rise of the original EDF remains. A response speed of less than a second can be realized.

    Regarding the control of the optical amplifying means 300, in order to drive the optical amplifying means 300 at a high speed in accordance with the level change of the input light, the PUMP-LD 320 is controlled by feed-forward using the input side TIA520 output information. At 403, the PUMP-LD 320 is driven using the control signal as an overshoot signal.

    In the differential operational amplifier 430 constituting this control means, by setting the + side input, the PUMP-LD can be driven with a desired drive current, so that EDF is possible.

    The high-speed variable optical attenuator (VOA) 620 is feedback-controlled by a difference signal between the output from the second input monitor unit 560 and the output from the output light monitor unit 700.

    Note that the PID circuit unit 405 in the feedback control unit 800 can also overshoot the drive signal of the VOA 620.

    Furthermore, automatic level control is also possible in which the VOA 520 is feedback-controlled so that the output becomes a constant level based on the output TIA 521 output information. In addition, a VOA input light monitor is inserted immediately before the VOA 520, and feedforward control of the VOA 520 can be performed based on a light intensity signal obtained from the VOA input light monitor. Furthermore, the drive signal of the VOA 620 in the feed forward control of the VOA 520 can be an overshoot signal.

    Next, a VOA drive circuit will be described. FIG. 9 shows an example of a VOA drive circuit. In this example, two identical circuits are stacked and large amplitude driving is realized by applying driving voltages on the + side and − side to both ends of the VOA. The devices used are 2SC3423 and 2SA1360 shown in the figure as commercially available high-current transistors.

    FIG. 10 shows a simulation waveform of the drive waveform in this circuit. However, the result is only for the circuit on the + side, but since the result on the − side is the same and has a different polarity, the VOA application amplitude is 40V. From this simulation result, it can be seen that the drive output of 1 microsecond or less is at most 40V.

    Therefore, it can be seen that a VOA having a driving voltage of 40 V or less and having a high-speed response performance is required.

    Therefore, the electro-optic type is prominent in that it has high-speed performance, and further, for example, the PLZT type high-speed VOA of International Publication No. WO / 2005/121876 is prominent as a voltage reduced to 40 V or less. .

    As an example of the VOA, an electro-optic type is shown, but the attenuation is varied by attenuating the input light and giving a drive signal, and the fluctuation of 6 dB before and after the drive signal is given can be varied within 10 microseconds or less. Any principle such as a mechanical type, a MEMS type, a magneto-optical type, a liquid crystal type, an electroabsorption type, or a thermo-optical type may be used as long as it has high-speed response performance.

    With this configuration, the PUMP-LD 320 is driven at a high speed according to the square wave input light, and an output waveform of the EDF 350 having a quick response component and a slow response component is obtained. The slow response component of the EDF 350 is removed by the VOA 620, and the output light 20 is shaped into a square wave, and a desired high-speed response is obtained.

    On the other hand, since the amount of the slow-response component to be deleted by the VOA 620 decreases, the drive voltage of the VOA 620 can be reduced and the response speed of the VOA 620 can be increased. Due to these synergistic effects, the output waveform is shaped and a response of 1 microsecond or less is obtained.

    By using the delay means 900 and the overshoot signal, it becomes possible to follow high-speed input optical signal fluctuations. By using feedback control using high-speed output variable means as in this embodiment, It is possible to follow a longer time square wave.

The conditions and experimental results (FIG. 11) in the configuration shown in FIG. 7 will be described. The applied EDF has an erbium concentration of 7.9 × 10 ²⁴ m ⁻³ and a length of 15 m.

    The wavelength of PUMP-LD was 0.98 μm and the maximum power was +23.5 dBm. The current for driving the PUMP-LD was a steady-state value of 370 mA and an overshoot current of 200%. The gain of the entire amplifier was set to 17 dB.

    The delay fiber was a single mode fiber of 5 km and had a delay amount of about 5 μsec.

    A VOA having a drive voltage amplitude of 30 V and a response speed of 1 microsecond or less was applied. Note that the gain of the entire amplifier was set to 20 dB.

    The measurement result of the output under these conditions is shown in FIG. It can be seen that a rectangular wave with a long period of 1 msec or more is following.

    In the measurement, a light source with a wavelength of 1550 μm is used, and the light input changes in a step shape to −4 dBm with respect to a reference level of −25 dBm.

    Note that the present invention is not limited to the above-described embodiments, and can be implemented by modifications without departing from the spirit of the invention.

    According to the present invention, since an optical amplifier capable of high-speed response can be realized, it can be used as an optical communication device.

  Illustration of overshoot signal   PID circuit configuration example   Configuration diagram of Embodiment 1 of the present invention   Illustration of relationship between overshoot amount and EDF response speed   Relationship between overshoot and delay   Experimental results of Embodiment 1 of the present invention   Configuration diagram of Embodiment 2 of the present invention   Explanation of the principle of the high-speed output variable means introduction effect   VOA drive circuit configuration example diagram   Example of simulation results for VOA drive circuit   Experimental results of Embodiment 2 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Input light 20 Output light 30 Electric signal 40 output from TIA Electric signal 50 output from PID Pumping light output from PUMP-LD 300 Optical amplification medium 310 Optical amplification means 320 PUMP-LD
330 PUMP-LD Drive Circuit 400 Feedforward Control Unit 410 Comparison Unit 420 Gain Setting Terminal 430 OPAMP
440 PID circuit 500 Input monitoring means 510 TAP-PD
520 TIA
550 First input monitoring means 560 Second input monitoring means 610 High-speed output variable means 620 High-speed variable optical attenuator (VOA)
630 VOA driving circuit 700 Output light monitoring means 800 Feedback control means 810 OPAMP
900 Optical delay means 910 Optical delay fiber

Claims (23)

  Control for performing feedforward control for amplification control of the optical amplifying means using at least the input monitoring means, optical amplifying means, optical delay means arranged in the preceding stage of the optical amplifying means, and the input monitoring means An optical amplifier comprising an overshoot signal for the amplification control.   2. The optical amplifier according to claim 1, further comprising: a signal branching unit that branches an electric signal output from the input monitor unit; and an electric signal delaying unit that delays one of the branched electric signals.   3. The optical amplifier according to claim 1, wherein the control means includes an overshoot generation circuit.   4. The optical amplifier according to claim 3, wherein the overshoot generation circuit is a PID circuit.   5. The optical amplifier according to claim 1, wherein the optical delay means is a variable optical delay means.   6. The optical amplifier according to claim 1, wherein the overshoot generation circuit is driven using a signal of the input monitor means.   7. The optical amplifier according to claim 1, wherein the variable optical delay means is driven using a signal from the input monitor means.   8. The optical amplifier according to claim 1, further comprising a high-speed output variable unit at a subsequent stage of the optical amplification medium.   9. The optical amplifier according to claim 8, further comprising an output light monitoring unit, wherein the high-speed output variable unit is driven using a signal from the output light monitoring unit.   9. The optical amplifier according to claim 8, wherein the high-speed output variable means is driven using a difference signal between the signal from the input monitor means and the signal from the output light monitor means.   11. The optical amplifier according to claim 8, wherein the high-speed output variable means is a high-speed variable optical attenuator.   The optical amplifier according to claim 11, wherein the high-speed variable optical attenuator includes an electro-optic effect element, and a driving voltage of the high-speed variable optical attenuator is 40 V or less.   An optical amplifying unit; an optical delay unit disposed in front of the optical amplifying unit; a first input monitoring unit disposed in front of the optical delay unit; and a second input disposed in a subsequent stage of the optical delay unit. An optical amplifier including a monitoring unit and a control unit for performing feedforward control for amplification control of the optical amplification unit using the first input monitoring unit, and using an overshoot signal for the amplification control An optical amplifier.   14. The optical amplifier according to claim 13, wherein the control means includes an overshoot generation circuit.   15. The optical amplifier according to claim 14, wherein the overshoot generation circuit is a PID circuit.   16. The optical amplifier according to claim 13, wherein the optical delay means is a variable optical delay means.   17. The optical amplifier according to claim 13, wherein the overshoot generation circuit is driven using a signal of the first input monitor means.   18. The optical amplifier according to claim 13, wherein the variable optical delay means is driven using a signal from the first input monitor means.   The optical amplifier according to any one of claims 13 to 18, further comprising high-speed output variable means at a subsequent stage of the optical amplification medium.   20. The optical amplifier according to claim 19, further comprising an output light monitor means, wherein the high speed output variable means is driven using a signal from the output light monitor means.   20. The optical amplifier according to claim 19, wherein the high-speed output variable means is driven by a difference signal between a signal from the second input monitor means and a signal from the output light monitor means.   The optical amplifier according to any one of claims 19 to 21, wherein the high-speed output variable means is a high-speed variable optical attenuator.   The optical amplifier according to claim 22, wherein the high-speed variable optical attenuator includes an electro-optic effect element, and a driving voltage of the high-speed variable optical attenuator is 40 V or less.

Images