JP2014236208A - Control method of optical amplifier and optical amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of an optical amplifier capable of enhancing the stability of characteristics during steady-state, while suppressing variation of output light power during transient time, and to provide an optical amplifier.SOLUTION: A control method of an optical amplifier for detecting the power of input light or output light of at least one optical amplifier outputting the inputted light while amplifying, and performing feedback control of the operation of the optical amplifier depending on the optical power thus detected includes a step for calculating the variation of the input light power or output light power of the optical amplifier, a step for determining whether the state of the input light or output light is transient state or steady state based on the variation, a step for selecting and setting any one of more than one type of control constants, depending on the determination result of transient state or steady state, and a step for feedback controlling the operation of the optical amplifier by using the control constants thus set.

Description

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

  In an optical communication system using a wavelength division multiplexing (WDM) transmission technique, it is required to ensure the reliability and quality of a transmission path and to operate efficiently, and a photo network capable of high-speed and large-capacity transmission. Has evolved into In such a photo network, the optical power level in the transmission path may change frequently and frequently due to switching of the optical transmission path or occurrence of a failure. For example, when a signal channel of wavelength multiplexed signal light is added / dropped, the optical power level input to an erbium-doped fiber amplifier (EDFA) installed in the transmission line changes rapidly. As a result, the inversion distribution state inside the EDF also changes abruptly, so that overshoot or undershoot occurs in the output light power level from the EDA of the signal channel (residual signal channel) other than the channel to be added / dropped. Such fluctuations in the output optical power due to the transient response of the optical amplifier are caused by transmission errors and optical errors caused by deviation from the dynamic range of each optical device such as an optical receiver and optical amplifier connected downstream of the optical amplifier. Causes damage to the device due to surge. Therefore, an optical amplifier control mechanism that can suppress the overshoot / undershoot amount of the output optical power instantaneously with respect to these fluctuations is desired.

  In Patent Document 1, the fluctuation of the output light power when the input light power fluctuates is suppressed by adjusting the control constant of the constant gain control means based on the input light power or the output light power to the optical amplifying unit. . On the other hand, in Patent Document 2, when the optical amplification means is controlled by feedforward control according to the input monitor signal, the control signal is an overshoot signal, thereby improving the slow response performance inherent to the optical amplification medium. And high speed response.

Japanese Patent No. 3998430 JP 2008-300812 A

  However, in the case of simple control constant adjustment by the above-mentioned feedforward control or feedback control, the steady state characteristics and the transient characteristics have a trade-off relationship, and the optimum characteristics are obtained in both the steady state and the transient state. It was difficult to realize. On the other hand, in recent years, it has been demanded that the stability of the steady-state characteristic is high while suppressing fluctuations in the output optical power of the optical amplifier during the transient, and there is also a trade-off between the transient characteristic and the frequency characteristic. Therefore, excellent frequency characteristics are also required.

  The present invention has been made in view of the above, and can suppress the fluctuation of the output light power during the transition, can improve the stability of the characteristic at the steady state, and can obtain the excellent frequency characteristic. An object of the present invention is to provide an amplifier control method and an optical amplifier.

  In order to solve the above-described problems and achieve the object, an optical amplifier control method according to the present invention detects the power of input light or output light of at least one optical amplifier that amplifies and outputs input light. An optical amplifier control method that feedback-controls the operation of the optical amplifier according to the detected optical power, the step of calculating a change amount of input optical power or output optical power of the optical amplifier, and the change A step of determining whether the state of the input light or the output light is in a transient state or a steady state based on the amount, and depending on whether the determination result is a transient state or a steady state, one of two or more types of control constants A step of selecting and setting one of them, and a step of feedback-controlling the operation of the optical amplifier using the set control constant.

  The method for controlling an optical amplifier according to the present invention is characterized in that, in the above-described invention, when the feedback control constant is changed in the setting step, the timing for changing is adjusted.

  The method for controlling an optical amplifier according to the present invention is the above-described method, wherein, in the setting step, the detection period of the input light or the output light of the optical amplifier, the time interval for calculating the change amount of the optical power, or the determination The timing for the change is adjusted according to a threshold value when performing the operation.

  The optical amplifier control method according to the present invention is the optical amplifier control method according to the present invention, wherein a waiting time is provided from the time of fluctuation of the input light or output light until the control constant is set, or the amount of change in the optical power determines the determination. The timing for the change is adjusted by providing a waiting time until the control constant is set after exceeding or falling below a threshold value when performing.

  The method for controlling an optical amplifier according to the present invention is characterized in that, in the above-described invention, the method further includes a step of calculating the control constant according to a predetermined control constant calculation model.

  The method for controlling an optical amplifier according to the present invention further includes a step of detecting input optical power of the optical amplifier and performing feedforward control of the operation of the optical amplifier based on the detected input optical power in the above invention. It is characterized by.

  An optical amplification apparatus according to the present invention includes at least one optical amplifier that amplifies and outputs input light, a photodetector that detects input light or output light power of the optical amplifier, and an input of the optical amplifier. A change amount calculation unit that calculates a change amount of optical power or output light power; a determination unit that determines whether the state of the input light or output light is in a transient state or a steady state based on the change amount; and the determination result Depending on whether the signal is in a transient state or a steady state, the photodetector detects using a setting unit that selects and sets one of two or more control constants and the set control constant And a control unit that feedback-controls the operation of the optical amplifier in accordance with optical power.

  The optical amplification device according to the present invention is characterized in that, in the above invention, the setting unit adjusts the timing to change when the feedback control constant is changed.

  In the optical amplifying device according to the present invention as set forth in the invention described above, when the setting unit performs the detection period of the input light or the output light of the optical amplifier, the time interval for calculating the amount of change in the optical power, or the determination. The change timing is adjusted according to the threshold value.

  In the optical amplifying device according to the present invention, in the above invention, the setting unit may provide a waiting time until the control constant is set from when the input light or the output light fluctuates, or the amount of change in the optical power is The timing of the change is adjusted by providing a waiting time until the control constant is set after exceeding or falling below a threshold for the determination.

  The optical amplifying device according to the present invention is characterized in that, in the above-mentioned invention, the optical amplifying device further comprises a calculating unit that calculates the control constant according to a predetermined control constant calculation model.

  The optical amplifying device according to the present invention is characterized in that, in the above invention, the optical amplifying device further includes a feedforward control unit that feedforward-controls the operation of the optical amplifier based on the input optical power detected by the photodetecting unit.

  According to the present invention, it is possible to increase the stability of the steady-state characteristic while suppressing fluctuations in the output light power during the transition, and to obtain an excellent frequency characteristic.

FIG. 1 is a block diagram showing the configuration of the optical amplifying device according to the first embodiment. FIG. 2 is a block diagram of the control circuit shown in FIG. FIG. 3 is a flowchart showing a control flow of the optical amplifier in the optical amplifying apparatus shown in FIG. FIG. 4 is a time chart when the control flow diagram shown in FIG. 3 is applied. FIG. 5 is a diagram illustrating an example of a simulation result in which the frequency characteristics of the phase and the frequency characteristics of the gain are combined into one. FIG. 6 is a flowchart showing a first modification of the control flow in the optical amplifying device shown in FIG. FIG. 7 is a flowchart showing a second modification of the control flow in the optical amplifying device shown in FIG. FIG. 8 is a block diagram illustrating a configuration of an optical amplifying device according to a comparative embodiment. FIG. 9 is a diagram showing the change over time of input / output power in the optical amplifying device shown in FIG. FIG. 10 is a diagram showing the temporal change in input / output power in the optical amplifying device shown in FIG. 1 when the control flow diagram of Modification 2 shown in FIG. 7 is applied. FIG. 11 is a flowchart showing a third modification of the control flow in the optical amplifying device shown in FIG. FIG. 12 is a block diagram illustrating a configuration of the optical amplifying device according to the second embodiment. FIG. 13 is a block diagram illustrating a configuration of the optical amplifying device according to the third embodiment. FIG. 14 is a diagram illustrating the characteristics of the control constant calculation models AA and BB. FIG. 15 is a flowchart showing a control flow in the optical amplifying device shown in FIG. FIG. 16 is a block diagram illustrating a configuration of the optical amplifying device according to the fourth embodiment.

  Embodiments of an optical amplifier control method and an optical amplifier according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Moreover, in each drawing, the same code | symbol is attached | subjected suitably to the same or corresponding element.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an optical apparatus according to Embodiment 1 of the present invention. This optical amplifying apparatus 100 includes an optical amplifier 4 having an erbium-doped optical fiber (EDF) 1, a WDM optical coupler 2, a pumping laser diode (LD) 3, optical couplers 5 and 7, and a photodiode (Photo Diodes: PD) 6 and 8, monitor circuits 9 and 10, control circuit 11, monitor value recording unit 12, change amount calculation unit 13, and control constant adjustment unit 14.

Hereinafter, each component will be specifically described.
Signal light, which is WDM signal light composed of a signal channel having a wavelength (for example, a wavelength of 1530 nm to 1610 nm) that can be optically amplified by the EDF 1, is input to the optical amplification device 100 from the optical input side.

  The optical coupler 5 branches a part (for example, intensity of 1% to 5%) of the signal light input to the optical amplifying apparatus 100 from the optical input side to the PD 6 side, and outputs the remainder to the optical amplifier 4. In the optical amplifier 4, the excitation LD 3 is supplied with driving power from the control circuit 11, and is excitation light that is laser light having a wavelength (for example, 0.98 μm wavelength band or 1.48 μm wavelength band) that can optically excite erbium ions contained in the EDF 1. Is output. The WDM optical coupler 2 multiplexes the signal light output from the optical coupler 5 and the pumping light output from the pumping LD 3. In the EDF 1, erbium ions optically excited by excitation light optically amplify signal light. As a result, the optically amplified signal light is output from the optical amplifier 4.

  The optical coupler 7 branches a part (for example, intensity of 1% to 5%) of the signal light amplified and output from the optical amplifier 4 to the PD 8 side, and outputs the remainder to the outside of the optical amplifying apparatus 100.

  The PD 6 receives a part of the input signal light branched by the optical coupler 5 and outputs a current signal corresponding to the received light intensity to the monitor circuit 9. The monitor circuit 9 is composed of, for example, a logarithmic conversion circuit, and detects the power of light input to the optical amplifying device 100 from the value of the current signal input from the PD 6. The monitor circuit 9 outputs a voltage signal Vin indicating the detected power of the input light to the control circuit 11.

  Similarly, the PD 8 receives a part of the output signal light branched by the optical coupler 7 and outputs a current signal corresponding to the received light intensity to the monitor circuit 10. The monitor circuit 10 is composed of, for example, a logarithmic conversion circuit, and detects the power of light output from the optical amplifying device 100 from the value of the current signal input from the PD 8. The monitor circuit 10 outputs a voltage signal Vout indicating the detected power of the output light to the control circuit 11.

  Based on the input voltage signal, the control circuit 11 supplies driving power to the pumping LD 3 so that the optical amplifying apparatus 100 performs an ALC (Automatic Level Control) operation or an AGC (Automatic Gain Control) operation. The operation of the amplifier 4 is controlled. Here, the ALC operation is an operation in which the power of light output from the optical amplifying apparatus 100 becomes constant. Control in which the control circuit 11 performs the ALC operation of the optical amplifying apparatus 100 in this way is referred to as ALC control. The AGC operation is an operation in which the amplification gain (that is, the ratio of the output light power to the input light power) becomes constant. Control in which the control circuit 11 performs the AGC operation of the optical amplifying apparatus 100 in this way is referred to as AGC control.

  The control circuit 11 is configured to perform AGC control by feedback control using PI (Proportional Integral) control or PID (Proportional Integral Derivative) control. Here, it is assumed that the control circuit 11 is configured to use PID control. FIG. 2 is a block diagram of the control circuit 11 shown in FIG. As shown in FIG. 2, the control circuit 11 includes a target gain setting unit 11a, a gain deviation detection unit 11b, a proportional circuit 11c, an integration circuit 11d, a differentiation circuit 11e, an addition circuit 11f, and an LD current control circuit. 11g.

The output signal from the monitor circuit 9, the output signal from the monitor circuit 10, and the target gain value G0 from the target gain setting unit 11a are input to the gain deviation detector 11b. The gain deviation detection unit 11b calculates a deviation ΔG between the gain (measurement gain) Gmon of the optical amplification device 100 based on the detection and the target gain G0, and this deviation ΔG is sent to the proportional circuit 11c, the integration circuit 11d, and the differentiation circuit 11e. Output. The deviation ΔG is expressed by the following equation.
ΔG = G0-Gmon

  The proportional circuit 11c outputs a proportional gain Kp corresponding to the input deviation ΔG. Further, the integration circuit 11d outputs an integration gain Ki corresponding to ΔG. The differentiation circuit 11e outputs a differential gain Kd corresponding to ΔG.

These output values Kp, Ki, Kd are input to the adder circuit 11f. The adder circuit 11f adds these values to calculate an LD current value I0 shown in the following equation.
I0 = Kp + Ki + Kd

  The adder circuit 11f outputs the calculated LD current value I0 to the LD current control circuit 11g. The LD current control circuit 11g controls the current of the excitation LD3 by outputting the LD current value I0 to the excitation LD3.

  Here, as described above, the signal light input to the optical amplifying apparatus 100 is WDM signal light, and the steady state in which the number of signal channels and the optical power of the entire signal light are constant, and OADM (Optical Add-Drop Multiplexer) ) And the like are added / dropped by the wavelength multiplexing / demultiplexing means, and the number of signal channels and the optical power of the entire signal light may be in a transient state. As described above, when the signal light input to the optical amplifying device 100 is in a steady state or a transient state, the signal light output from the optical amplifying device 100 is also in a steady state or a transient state.

  In this optical amplifying apparatus 100, the monitor value recording unit 12, the change amount calculating unit 13, and the control constant adjusting unit 14 are provided, so that the operation of the optical amplifier 4 can be performed according to whether it is a steady state or a transient state. A control constant for feedback control is set.

  Hereinafter, operations of the monitor value recording unit 12, the change amount calculation unit 13, and the control constant adjustment unit 14 will be described with reference to the control flowcharts of FIGS.

  First, the monitor circuit 9 monitors the input optical power Pin (t) at time t and outputs the monitor value as a voltage signal (step S1). The monitor circuit 9 performs monitoring at a predetermined repetition period m. Next, the monitor value recording unit 12 receives the monitor values monitored by the monitor circuit 9 and sequentially records them (step S2).

  Next, the change amount calculation unit 13 monitors the input optical power Pin (t) at time t, and the monitored value of the input optical power Pin (t−x) before time x for a certain period from time t. Is calculated from the monitor value recording unit 12 and the change amount ΔPin = | Pin (t−x) −Pin (t) | of the input optical power is calculated and output to the control constant adjustment unit 14 (step S3).

  Next, the control constant adjusting unit 14 stores therein control constants A and B and a threshold value a, and determines whether ΔPin exceeds the threshold value a (step S4). If ΔPin exceeds the threshold value a (step S4, Yes), it is determined that the state of the input light is a transient state, and the control constant A used during the transition is selected as the control constant. Then, the selected control constant A is output to the control circuit 11, the control constant used in the control circuit 11 is set to the selected control constant A (step S5), and the process returns to step S1.

  On the other hand, if ΔPin does not exceed the threshold value a (No in step S4), it is determined that the state of the input light is a steady state, and the control constant B used in the steady state is selected as the control constant. Then, the selected control constant B is output to the control circuit 11, the control constant used in the control circuit 11 is set to the selected control constant B (step S6), and the process returns to step S1.

  In step S3, the change ΔPin of the input optical power is related to the monitored value of the input optical power Pin (t) at time t and the monitored value of the input optical power Pin (t−x) at time t−x. However, instead of the monitored value of the input optical power Pin (t-x) at the time tx, the monitored value of the input optical power Pin (t) at the time t and the input optical power at the time tx An average value with the monitor value of Pin (t−x) may be used.

  In step S5, when the control constant used in the control circuit 11 at the time of setting is the control constant A, setting to the control constant A means that the control constant used is maintained at the control constant A. To do. Further, when the control constant used in the control circuit 11 at the time of setting is the control constant B, setting to the control constant A means that the control constant to be used is changed to the control constant B. The same applies to step S6.

  FIG. 4 is a time chart when the control flow diagram shown in FIG. 3 is applied. The optical monitor value shown in the upper part of FIG. 4 indicates the monitor value of the input optical power, and the change amount shown in the lower part indicates the change amount ΔPin of the input optical power. The control flow in FIG. 3 is repeated at a repetition frequency m (repetition period 1 / m). When the light monitor value changes as shown in FIG. 4, it is determined that ΔPin does not exceed the threshold value a until time t1, and the control constant B used in the steady state is selected and set as the control constant. Next, at time t1, it is determined that ΔPin has exceeded the threshold value a, and the control constant is changed to the control constant A used during transition. Furthermore, at time t2, it is determined that ΔPin has fallen below the threshold value a (not exceeding the threshold value a), and the control constant is changed to a control constant B that is used in a steady state.

  As described above, the control constant for feedback control of the operation of the optical amplifier 4 is selected and set depending on whether the state of the input light is a steady state or a transient state. Here, the control constant A is a value that is more suitable for control during transition, and the control constant B is a value that is suitable for control during steady state. For example, when the control constant to be set is a proportional constant in the proportional circuit 11c (a constant for determining the proportional gain Kp), the control constant A is set to a value larger than the control constant B.

  FIG. 5 is a diagram illustrating an example of a simulation result in which the frequency characteristics of the phase and the frequency characteristics of the gain are combined into one. Here, the unit of phase and gain is an arbitrary unit, and the frequency range is 10 MHz or less. The vertical axis is represented by ΔG. The control constant A is a value suitable for control during transition, and the control constant B is a value suitable for control during steady state.

  As described above, in the optical amplifying apparatus 100 according to the first embodiment, the optical amplifier 4 is feedback-controlled using the control constant selected according to whether the state of the input light is the transient state or the steady state. Therefore, the trade-off relationship between the steady state characteristics and the transient characteristics is eliminated. As a result, in this optical amplifying apparatus 100, the stability of the steady-state characteristics can be enhanced while suppressing fluctuations in the output optical power during the transition.

(Modification 1)
FIG. 6 is a flowchart showing a first modification of the control flow in the optical amplifying apparatus 100 shown in FIG. In the control flow of the first modification, the threshold value a of the change amount of the optical power for changing the control constant from the transient time to the steady state is different from the threshold value b of the change amount of the optical power for changing the control constant from the steady time to the transient time. Value.

  This will be specifically described below. Steps S1 to S3 are performed in the same manner as in FIG. That is, first, the monitor circuit 9 monitors the input optical power Pin (t) at time t and outputs the monitor value as a voltage signal (step S1). Next, the monitor value recording unit 12 receives the monitor values monitored by the monitor circuit 9 and sequentially records them (step S2).

  Next, the change amount calculation unit 13 monitors the input optical power Pin (t) at time t, and the monitored value of the input optical power Pin (t−x) before time x for a certain period from time t. Is calculated from the monitor value recording unit 12 and the change amount ΔPin = | Pin (t−x) −Pin (t) | of the input optical power is calculated and output to the control constant adjustment unit 14 (step S3).

  Next, the control constant adjustment unit 14 stores therein control constants A and B and threshold values a and b, and determines whether or not the current control constant setting is the control constant B (step S7). . When it is the control constant B (step S7, Yes), it is determined whether or not ΔPin exceeds a set threshold value a (step S4). If ΔPin exceeds the threshold value a (step S4, Yes), it is determined that the state of the input light is a transient state, and the control constant A used during the transition is selected as the control constant. Then, the selected control constant A is output to the control circuit 11, the control constant used in the control circuit 11 is set to the selected control constant A (step S5), and the process returns to step S1. If ΔPin does not exceed the threshold value a (No in step S4), the process returns to step S1 with the control constant set to the control constant B.

  On the other hand, if it is not the control constant B (the control constant A) (step S7, No), it is determined whether or not ΔPin is below a set threshold value b (step S8). When ΔPin is lower than the threshold value b (step S8, Yes), it is determined that the state of the input light is a steady state, and the control constant B used at the steady state is selected as the control constant. Then, the selected control constant B is output to the control circuit 11, the control constant used in the control circuit 11 is set to the selected control constant A (step S6), and the process returns to step S1. If ΔPin is not less than the threshold value b (step S8, No), the process returns to step S1 with the control constant set to the control constant A.

  In this way, the threshold value a of the change amount of the optical power that changes the control constant from the transient time to the steady state and the threshold value b of the change amount of the optical power that changes the control constant from the steady time to the transient time are set to different values. The timing for changing the control constant can be optimized in the case of transition from transient to steady state and in the case of steady state to transition. For example, when performing PI control, if the threshold value is one, the control constant may be returned to the steady state before the accumulated value of the deviation of the integral gain of PI control becomes sufficiently small. Overshoot / undershoot may occur. On the other hand, the occurrence of such overshoot / undershoot can be suppressed or prevented by providing two different threshold values.

(Modification 2)
FIG. 7 is a flowchart showing a second modification of the control flow in the optical amplifying apparatus 100 shown in FIG. In the control flow of the second modification, a waiting time is provided from when the state is determined until the control constant is set, and the timing for setting or changing the control constant is adjusted. Thus, a predetermined waiting time is given from when the input optical power varies until the control constant is set and until the control constant is set after the change amount of the optical power exceeds or falls below the threshold value.

  In the control flow of the modification 2, the same control as the control flow shown in FIG. 3 is performed, but differs in the following points. That is, in the control flow of the modified example 2, when it is determined in step S4 that ΔPin exceeds the set threshold value a (step S4, Yes), it is determined that the state of the input light is a transient state. The control constant A is selected as the control constant, and then a predetermined waiting time TA is provided (step S9). Then, after the waiting time TA has elapsed, the selected control constant A is output to the control circuit 11, the control constant used in the control circuit 11 is set to the selected control constant A (step S5), and the process returns to step S1.

  Similarly, when it is determined that ΔPin does not exceed the threshold value a (step S4, No), it is determined that the state of the input light is a steady state, and the control constant B is selected as the control constant. Waiting time TB is provided (step S10). Then, after the waiting time TB has elapsed, the selected control constant B is output to the control circuit 11, the control constant used in the control circuit 11 is set to the selected control constant B (step S6), and the process returns to step S1.

  In particular, when the control constant is changed from the control constant B at the time of steady state to the control constant A at the time of transition in Step S5, an appropriate waiting time TA is set, and the timing of the transition is adjusted by adjusting the timing of the change. The amount of overshoot / undershoot can be further suppressed. On the other hand, in step S6, when the control constant is changed from the control constant A during the transition to the control constant B during the steady state, an appropriate waiting time TB is set and the change timing is adjusted so that Since it is possible to converge to a stable control state in a short time, the stability at the steady state is increased.

  The waiting times TA and TB are set according to the control configuration (for example, the configuration of only the feedback control or the configuration of the feedback control and the feedforward control described later), the speed and amount of change of the optical power, etc. Accordingly, the above-described overshoot / undershoot amount at the time of transition can be suppressed, and the setting can be appropriately set so as to realize a short time convergence to a stable control state at the steady state. Alternatively, the waiting times TA and TB are set by setting the repetition period m, which is the detection period of the input optical power, the time x, which is the time interval for calculating the change amount ΔPin of the input optical power in the change amount calculation unit 13, and the threshold value. You may set according to (a and b).

  Next, in the case where the control flow of the second modification shown in FIG. 7 is performed in the optical amplifying device 100 according to the first embodiment, and in the case of the optical amplifying device according to the comparative embodiment in which the control constant is not changed, AGC is performed. Control was performed and the characteristics were simulated.

  FIG. 8 is a block diagram illustrating a configuration of an optical amplifying device according to a comparative embodiment. The optical amplifying apparatus 1000 according to this comparative embodiment has a configuration in which the monitor value recording unit 12, the change amount calculating unit 13, and the control constant adjusting unit 14 are deleted from the optical amplifying apparatus 100 according to the first embodiment. The control circuit 11 performs AGC control with a fixed control constant.

  A description will be given of a simulation result of optical output when Addition of a signal channel is generated in input light and the input optical power increases with a rise time of 100 μs in the optical amplification apparatuses 100 and 1000 controlled by AGC.

  FIG. 9 is a diagram showing a change with time of input / output power in the optical amplifying apparatus 1000 according to the comparative example shown in FIG. The time change of the output light power is indicated as a gain change (Δgain). The output light 1 shows a case where AGC control is performed using only the control constant A used during transition. The output light 2 shows a case where AGC control is performed using only the control constant B used in the steady state. In FIG. 9, a part of the waveform of the output light in a steady state (about −0.2 ms) is shown enlarged.

  As shown in FIG. 9, the input light has a power that increases abruptly between 0 ms and 100 μs (0.1 ms) on the horizontal axis, and is in a transient state, but the power is constant at other times. , In steady state. At this time, in the case of the output light 1, the overshoot amount is small and the time until the gain converges is short compared to the case of the output light 2, and the transient characteristics are excellent. However, as shown in the enlarged region, the waveform The amplitude of is increased, and the stability at the steady state is poor. On the other hand, in the case of the output light 2, the amplitude of the waveform is small and the stability at the steady state is excellent compared to the case of the output light 1, but the overshoot amount is large and the transient characteristics are inferior. As described above, in the comparative embodiment, the transient characteristics and the steady characteristics are in a trade-off relationship.

  FIG. 10 is a diagram illustrating the time change of input / output power in the optical amplifying apparatus 100 when the control flow diagram of the second modification is applied. In the case of the output light 3, the waiting time TA is set to 0.03 ms, and the waiting time TB is set to 0.45 ms. In the case of the output light 4, the waiting time TA is set to 0 ms, and the waiting time TB is set to 0.1 ms.

  As shown in FIG. 10, in the case of the output light 4, both the suppression of the overshoot amount and the stability at the steady state are compatible as compared with the cases of the output lights 1 and 2 of the comparative form. In the case of the output light 3, the overshoot amount is further suppressed and the time until the gain converges is shorter than that in the case of the output light 4.

(Modification 3)
FIG. 11 is a flowchart showing a third modification of the control flow in the optical amplifying apparatus 100 shown in FIG.

  The control flow of Modification 3 is a combination of the control flow of Modification 1 shown in FIG. 6 and the control flow of Modification 2 shown in FIG. That is, in the control flow of the modified example 2, when it is determined in step S4 that ΔPin exceeds the set threshold value a (step S4, Yes), it is determined that the state of the input light is a transient state. The control constant A is selected as the control constant, and then a predetermined waiting time TA is provided (step S9). Then, after the waiting time TA has elapsed, the selected control constant A is output to the control circuit 11, the control constant used in the control circuit 11 is set to the selected control constant A (step S5), and the process returns to step S1.

  Similarly, when it is determined that ΔPin is below the threshold value b (step S8, Yes), it is determined that the state of the input light is a steady state, and the control constant B is selected as the control constant. Waiting time TB is provided (step S10). Then, after the waiting time TB has elapsed, the selected control constant B is output to the control circuit 11, the control constant used in the control circuit 11 is set to the selected control constant B (step S6), and the process returns to step S1.

  In the control flow of the third modification, both the effect of using the control flow of the first modification and the effect of using the control flow of the second modification are obtained.

(Embodiment 2)
FIG. 12 is a block diagram showing a configuration of an optical amplifying device according to Embodiment 2 of the present invention. As shown in FIG. 12, the optical amplifying apparatus 200 according to the second embodiment further includes a feedforward control unit 15 and an adder 16 in addition to the configuration of the optical amplifying apparatus 100 according to the first embodiment shown in FIG. It has an added configuration.

  A voltage signal Vin indicating the power of the detected input light is input from the monitor circuit 9 to the feedforward control unit 15. The feedforward control unit 15 outputs an added value I1 of the current value for the excitation LD3 based on the input voltage signal Vin. The feedforward control unit 15 stores a lookup table indicating the correspondence between the voltage signal Vin and the added value I1, and a calculation formula such as a linear expression for calculating the added value I1 from the voltage signal Vin. An added value I1 corresponding to the voltage signal Vin obtained by referring to the table or calculating using a calculation formula is output. The added value I1 is set so as to cancel out a sudden change in input optical power, for example, as in the technique described in Patent Document 2.

  The adder 16 adds the addition value I1 of the current value output from the feedforward control unit 15 to the LD current value I0 output from the control circuit 11, and outputs the LD current value (I0 + I1) to the excitation LD3. . As a result, the control circuit 11 and the feedforward control unit 15 perform both feedback control and feedforward control on the optical amplifier 4.

  In the optical amplifying apparatus 200 according to the second embodiment, the feedforward is performed together with the feedback control of the optical amplifier 4 using the control constant selected according to the state of the input light in the optical amplifying apparatus 100 according to the first embodiment. Since the control is also performed, it is possible to improve the suppression of fluctuations in the output optical power during the transition and the stability of the characteristics during the steady state.

(Embodiment 3)
FIG. 13 is a block diagram illustrating a configuration of the optical amplifying device according to the third embodiment. As shown in FIG. 13, the optical amplifying apparatus 300 according to the third embodiment further includes a control constant calculation model selection unit 17 based on the configuration of the optical amplifying apparatus 200 according to the second embodiment shown in FIG. In addition, the monitor circuit 10 has a configuration in which the voltage signal Vout indicating the detected power of the output light is also output to the control constant adjustment unit 14.

  The control constant adjustment unit 14 stores control constant calculation models AA and BB. FIG. 14 is a diagram illustrating the characteristics of the control constant calculation models AA and BB. These calculation models are calculation models that adjust the control constant of AGC control based on the input optical power or the output optical power to the optical amplifier, as in Patent Document 1, for example. As shown in FIG. 14, both of the control constant calculation models AA and BB are control constant calculation models in which the control constant value increases in proportion to the increase in output optical power.

  FIG. 15 is a flowchart showing a control flow in optical amplifying apparatus 300 according to the third embodiment shown in FIG.

  In FIG. 15, steps S1 to S3 are performed in the same manner as in FIG. That is, first, the monitor circuit 9 monitors the input optical power Pin (t) at time t and outputs the monitor value as a voltage signal (step S1). Next, the monitor value recording unit 12 receives the monitor values monitored by the monitor circuit 9 and sequentially records them (step S2).

  Next, the change amount calculation unit 13 records the monitor value of the input optical power Pin (t) at time t and the monitor value of the input optical power Pin (t−x) before x cycles from time t. Called from the unit 12, the input light power variation ΔPin = | Pin (tx) −Pin (t) | is calculated and output to the control constant calculation model selection unit 17 (step S3).

  Next, the control constant calculation model selection unit 17 determines whether or not ΔPin exceeds a predetermined threshold a (step S4). When ΔPin exceeds the threshold value a (step S4, Yes), it is determined that the state of the input light is in a transient state, and a control constant calculation model AA to be used at the time of transition is selected as a control constant calculation model, and control is performed. A command to use the constant calculation model AA is output to the control constant adjustment unit 14. The control constant adjusting unit 14 sets a model to be used as the control constant calculation model AA based on the input command (step S11). Then, the control constant adjusting unit 14 calculates a control constant from the voltage signal Vout indicating the detected power of the output light by using the control constant calculation model AA (step S13). Then, the calculated control constant is output to the control circuit 11, and the process returns to step S1.

  Further, if ΔPin does not exceed the threshold value a (No in step S4), the control constant calculation model selection unit 17 determines that the state of the input light is in a steady state, and uses it as a control constant calculation model in a steady state. The control constant calculation model BB to be selected is selected, and a command to use the control constant calculation model B is output to the control constant adjustment unit 14. The control constant adjusting unit 14 sets a model to be used as the control constant calculation model BB based on the input command (step S12). Then, the control constant adjusting unit 14 calculates a control constant from the voltage signal Vout indicating the detected power of output light using the control constant calculation model BB (step S13). Then, the calculated control constant is output to the control circuit 11, and the process returns to step S1.

  According to the optical amplifying apparatus 300 and its control flow according to the third embodiment, since the control constant can be set using a plurality of control constant calculation models, the fluctuation of the output optical power at the time of transition can be further suppressed and constant. The stability of the usual characteristics can be further increased.

(Embodiment 4)
FIG. 16 is a block diagram showing a configuration of an optical amplifying device according to Embodiment 4 of the present invention. As shown in FIG. 16, the optical amplifying apparatus 400 according to the fourth embodiment includes a monitor value recording unit 12, a change amount calculating unit 13, and the like in the configuration of the optical amplifying apparatus 100 according to the first embodiment shown in FIG. In addition, the control constant adjustment unit 14 is configured to operate with the output optical power monitored by the monitor circuit 10 on the optical output side.

  That is, the monitor value recording unit 12 receives the monitor values monitored by the monitor circuit 10 and sequentially records them. From the monitor value recording unit 12, the change amount calculation unit 13 obtains the monitor value of the output optical power Pout (t) at the time t and the monitor value of the output optical power Pout (t−x) before x cycles from the time t. Called, the output light power change amount ΔPout = | Pout (t−x) −Pout (t) | is calculated and output to the control constant adjustment unit 14.

  When the control constant adjustment unit 14 determines that ΔPout exceeds a predetermined threshold, the control constant adjustment unit 14 determines that the state of the input light is a transient state, and selects the control constant A to be used during the transition as the control constant. The control constant A is output to the control circuit 11, and the control constant used in the control circuit 11 is set as the control constant A.

  On the other hand, if it is determined that ΔPout does not exceed the predetermined threshold value, it is determined that the input light is in a steady state, and the control constant B used in the steady state is selected as the control constant, and the control constant B is controlled. The control constant used in the control circuit 11 is set to the control constant B.

  Since the configuration of the optical amplifying apparatus 400 according to the fourth embodiment monitors the output optical power, the optical input state does not change when the optical amplifying apparatus is started or when the shutdown is canceled, but it is used in a transient state. The control constant A can be suitably applied when it is necessary to use the control constant A.

  In the above embodiment, the optical amplifying apparatus includes one optical amplifier. However, it may include a plurality of optical amplifiers and control them simultaneously.

  In the above embodiment, the optical amplifier is an EDFA. However, the present invention is not limited to the optical amplifier using an optical fiber to which an optical amplifying medium other than erbium is added, or a Raman optical amplifier. It can also be applied to an amplifier.

  In the above embodiment, there are two control constants or control constant calculation models to be selected and set. However, the control method and the optical amplifying apparatus according to the present invention include three or more control constants or control constants. It may be configured to select and set from a constant calculation model.

  The present invention is not limited to the above embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. For example, you may apply the control flow which provides the different threshold value and waiting time of the modifications 1-3 with respect to any of the optical amplifiers which concern on Embodiment 2-4. Further, the configuration in which the control constant is set based on the optical output power as in the fourth embodiment may be combined with the optical amplifying device according to the first to third embodiments. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

1 EDF
2 WDM optical coupler 3 Pumping LD
4 Optical amplifier 5, 7 Optical coupler 6, 8 PD
9, 10 Monitor circuit 11 Control circuit 11a Target gain setting unit 11b Gain deviation detection unit 11c Proportional circuit 11d Integration circuit 11e Differentiation circuit 11f Addition circuit 11g LD current control circuit 12 Monitor value recording unit 13 Change amount calculation unit 14 Control constant adjustment unit DESCRIPTION OF SYMBOLS 15 Feedforward control part 16 Adder 17 Control constant calculation model selection part 100, 200, 300, 400 Optical amplifier

Claims (12)

An optical amplifier control method that detects the power of input light or output light of at least one optical amplifier that amplifies and outputs input light, and feedback-controls the operation of the optical amplifier according to the detected optical power. There,
Calculating a change amount of input optical power or output optical power of the optical amplifier;
Determining whether the state of the input light or output light is a transient state or a steady state based on the amount of change;
Selecting and setting any one of two or more control constants depending on whether the determination result is a transient state or a steady state;
Feedback control of the operation of the optical amplifier using the set control constant;
An optical amplifier control method comprising:   The method for controlling an optical amplifier according to claim 1, wherein, in the step of setting, when the feedback control constant is changed, a change timing is adjusted.   In the setting step, the change timing is adjusted according to a detection period of input light or output light of the optical amplifier, a time interval for calculating a change amount of the optical power, or a threshold value when the determination is performed. The method of controlling an optical amplifier according to claim 2. Providing a waiting time from the time of fluctuation of the input light or output light until the control constant is set;
Alternatively, by providing a waiting time until the control constant is set after the amount of change in the optical power exceeds or falls below the threshold when the determination is performed,
4. The method of controlling an optical amplifier according to claim 2, wherein the timing for changing is adjusted.   5. The method of controlling an optical amplifier according to claim 1, further comprising a step of calculating the control constant according to a predetermined control constant calculation model.   6. The method according to claim 1, further comprising a step of detecting an input optical power of the optical amplifier and performing a feedforward control of an operation of the optical amplifier based on the detected input optical power. A method for controlling the optical amplifier according to claim. At least one optical amplifier for amplifying and outputting input light; and
A photodetector for detecting the power of input light or output light of the optical amplifier;
A change amount calculation unit that calculates a change amount of input optical power or output optical power of the optical amplifier;
A determination unit that determines whether the state of the input light or output light is a transient state or a steady state based on the amount of change;
A setting unit that selects and sets any one of two or more control constants according to whether the determination result is a transient state or a steady state;
A control unit that feedback-controls the operation of the optical amplifier according to the optical power detected by the photodetector using the set control constant;
An optical amplifying device comprising:   The optical amplifying apparatus according to claim 7, wherein the setting unit adjusts a change timing when the feedback control constant is changed.   The setting unit adjusts the change timing according to a detection period of input light or output light of the optical amplifier, a time interval for calculating a change amount of the optical power, or a threshold value when the determination is performed. The optical amplifying device according to claim 8. The setting unit
Providing a waiting time from the time of fluctuation of the input light or output light until the control constant is set;
Alternatively, by providing a waiting time until the control constant is set after the amount of change in the optical power exceeds or falls below the threshold when the determination is performed,
The optical amplifying apparatus according to claim 8, wherein the change timing is adjusted.   The optical amplifying apparatus according to claim 7, further comprising a calculating unit that calculates the control constant according to a predetermined control constant calculation model.   The optical amplification according to any one of claims 7 to 11, further comprising a feedforward control unit that feedforward-controls the operation of the optical amplifier based on the input optical power detected by the photodetection unit. apparatus.

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