JP2014053398A - Control method of optical module and optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deal with suppression of variation in the optical output for transient variation, and stability when switching the set value of output optical level, simultaneously without switching the circuit.SOLUTION: In an optical device 1 of an optical module with a control circuit, a high speed feedback loop having a relatively small time constant Tfor an optical amplification unit 11 comprises: an optical coupler 12; a PD monitor unit 14; an error amplifier 16; an LD drive unit 15; and an optical coupler 13. A low speed feedback loop having a time constant Tlarger than Tfor an optical amplification unit 11 comprises: an optical coupler 12; a PD monitor unit 14; an LD current setting unit 17; an error amplifier 16; an LD drive unit 15; and an optical coupler 13. A plurality of feedback loops are provided for the amplification unit or the optical attenuator of a general optical device, and configured to satisfy T<T, in the time constants T, Tof two feedback loops out of these feedback loops.

Description

  The present invention relates to an optical module control method and an optical apparatus used for optical communication.

  As conventional optical module control methods, those described in Patent Documents 1 and 2 are known.

  Patent Document 1 describes a method for controlling an optical amplifier, in which one monitoring target such as an input light monitor and an output light monitor is controlled by forming one loop. 11A and 11B are block diagrams of basic configurations using an analog control circuit and a digital control circuit in the optical device described in Patent Document 1.

  As shown in FIG. 11A, an optical device 110 using an analog control circuit according to the prior art includes a PD monitor unit including an optical amplifying unit 111 composed of an amplifying optical fiber, optical couplers 112 and 113, and a photodetector (PD) 114a. 114, and an LD driving unit 115 including a pump laser diode (pump LD) 115a that is an excitation light source, and an LD current setting unit 116 and an error amplification unit 117 that are analog control circuits. In this optical device 110, in order to make the intensity of the output light from the optical device 110 a constant level, the analog control circuit performs feedback control with one loop.

  In addition, as shown in FIG. 11B, the optical device 120 using the digital control circuit according to the prior art is replaced with a central processing unit (CPU) 126a, instead of the LD current setting unit 116 and the error amplification unit 117 of the optical device 110. A digital control unit 126 having an FPGA (Field Programmable Gate Array) 126b, a memory 126c, and an LD current setting unit 126d is provided. The optical amplifying unit 121, the optical couplers 122 and 123, the PD monitor unit 124 including the PD 124a, and the LD driving unit 125 including the pump LD 125a are the same as the corresponding elements of the optical device 110, respectively. In the optical device 120, in order to set the intensity of the output light from the optical device 120 to a constant level, the digital control unit 126 which is a digital control circuit performs feedback control with one loop.

  Patent Document 2 describes a configuration of an optical device that has two feedback loops and performs feedback control in one loop for each of two monitoring targets. The monitoring targets in these two feedback loops are the output light intensity from the optical device and the drive current value of the pump LD, respectively. FIG. 12 is a block diagram of a basic configuration of the optical device described in Patent Document 2. In FIG.

  As shown in FIG. 12, the optical device 130 described in Patent Document 2 includes an optical amplification unit 131, optical couplers 132 and 133, a PD monitor unit 134 including a PD 134a, an LD driving unit 135 including a pump LD 135a, and It has an LD current monitor unit 136, and a digital control unit 137 including a CPU 137a, a memory 137b, and an LD current setting unit 137c. In this optical device 130, one of the monitoring targets is the output light intensity from the optical device 130, and the other is the drive current value of the pump LD 135a.

JP 2006-128219 A Japanese Patent Laid-Open No. 11-135864

  However, in the control method described in Patent Document 1, there is one feedback control loop. Therefore, it is difficult to perform stable feedback control when events having different time constants occur. For example, it is difficult to suppress the fluctuation of the output light level with respect to the transient fluctuation of the input light level while ensuring the stability at the time of switching the set value of the output light level.

  Specifically, in the technique described in Patent Document 1, in order to suppress the occurrence of an unstable state such as an overshoot at the time of switching the set value of the output light level, an adjustment that makes the time constant of the feedback loop relatively large is performed. Do. However, in this case, it becomes difficult to suppress a change in the output light level with respect to a transient change such as a change in the input light level of about 5 dB / ms due to fiber handling or the like.

  Conversely, if the time constant of the feedback loop is made relatively small, it becomes possible to suppress changes in the output light level with respect to transient fluctuations. However, in this case, an unstable state such as an overshoot occurs when the set value of the output light level is switched, and further oscillation occurs. When a multi-stage amplification optical amplification system is constructed with such an optical fiber amplifier that can cause such an unstable state, the output light level at the subsequent optical fiber amplifier is reduced due to overshoot when the set value of the output light level is switched. It becomes extremely large and may adversely affect the light receiving part.

  In the control method described in Patent Document 2, the roles of the two feedback loops are different from each other. For this reason, it has not been possible to cope with both the stability at the time of switching the set value of the output light level and the suppression of the fluctuation of the output light level with respect to the transient fluctuation of the input light level.

  Specifically, in the configuration including two feedback loops described in Patent Document 2, one of the targets of monitoring of the two feedback loops is the output light intensity of the optical fiber amplifier, and the other is the drive current value of the excitation light source. It is. The feedback control for the drive current value of the excitation light source is to stabilize the intensity of the excitation light, so that stability when switching the set value of the output light level and suppression of fluctuations in the output light level with respect to transient fluctuations in the input light level. Does not contribute.

  The present invention has been made in view of the above, and its purpose is to suppress the change in the optical output with respect to the transient fluctuation of the input light and to ensure the stability at the time of switching the set value of the output light level. It is an object of the present invention to provide an optical module control method and an optical apparatus that can simultaneously handle the above without switching circuits.

  In order to solve the above-described problems and achieve the above object, an optical module control method according to the present invention detects optical output power in an optical module having a predetermined response time constant, and controls according to the detected optical output power. In the control method of an optical module in which the optical output of the optical module is feedback controlled by a circuit, the control circuit has a plurality of feedback loops including a first feedback loop and a second feedback loop, The time constant is set to be less than the time constant of the second feedback loop.

  The optical module control method according to the present invention is characterized in that, in the above invention, the time constant of the second feedback loop is 10 times or more of the time constant of the first feedback loop.

  In the control method of an optical module according to the present invention, in the above invention, the time constant of the first feedback loop is set to a time constant capable of suppressing the fluctuation of the output optical power with respect to the transient fluctuation of the input optical power input to the optical module. The time constant of the second feedback loop is set to a time constant capable of stabilizing the output optical power when the set value of the output optical power is switched.

  The optical module control method according to the present invention is characterized in that, in the above invention, the first feedback loop is configured by an analog control circuit, and the second feedback loop is configured by a digital control circuit.

  The optical module control method according to the present invention is characterized in that, in the above invention, the optical module is an optical amplifier. The optical module control method according to the present invention is characterized in that, in the above invention, the optical module is an optical variable attenuator.

  An optical apparatus according to the present invention is an optical apparatus having an optical module having a predetermined response time constant, and a control circuit that detects optical output power in the optical module and feedback-controls the optical output of the optical module according to the optical output power. The control circuit has a plurality of feedback loops including a first feedback loop and a second feedback loop, and the time constant of the first feedback loop is less than the time constant of the second feedback loop. Features.

  The optical device according to the present invention is characterized in that, in the above invention, the time constant of the second feedback loop is 10 times or more the time constant of the first feedback loop.

  The optical device according to the present invention is characterized in that, in the above invention, the first feedback loop is composed of an analog control circuit, and the second feedback loop is composed of a digital control circuit.

  The optical device according to the present invention is characterized in that, in the above invention, the optical module is an optical amplifier. In the optical device according to the present invention as set forth in the invention described above, the optical module is an optical variable attenuator.

  According to the optical module control method and the optical apparatus of the present invention, the feedback loop having a relatively small time constant suppresses the change in the optical output with respect to the transient fluctuation, and another feedback having a larger time constant than the feedback loop. Since the stability at the time of switching the set value of the output light level can be ensured by the loop, the circuit suppresses the change of the light output against the transient fluctuation and the stability at the time of switching the set value of the output light level. It is possible to respond simultaneously without switching.

FIG. 1 is a block diagram showing a configuration of an optical device according to the first embodiment of the present invention. FIG. 2A is a graph illustrating an example of a measurement waveform of input optical power during fiber handling. FIG. 2B is a graph showing an example of a measurement waveform of the output optical power during fiber handling when the optical device according to the embodiment of the present invention is used. FIG. 3 is a graph showing an example of a measurement waveform of the output optical power during fiber handling when the optical device according to the embodiment of the present invention is used. FIG. 4A is a graph illustrating an example of a measurement waveform of input optical power during fiber handling. FIG. 4B is a graph showing an example of a measurement waveform of output optical power during fiber handling when an optical device according to the related art is used. FIG. 5A is a graph illustrating an example of a measurement waveform of input optical power during fiber handling. FIG. 5B is a graph showing an example of a measurement waveform of output optical power during fiber handling when an optical device according to the related art is used. FIG. 6A is a graph showing an example of a measurement waveform of the output light power when the output light level setting value is switched when the optical device according to the embodiment of the present invention is used. FIG. 6B is a graph showing an example of a measurement waveform of the output light power when the output light level set value is switched when an optical device according to the related art is used. FIG. 7 is a block diagram showing a configuration of an optical device according to the second embodiment of the present invention. FIG. 8 is a block diagram showing a configuration of an optical device according to the third embodiment of the present invention. FIG. 9 is a block diagram showing a configuration of an optical device according to the fourth embodiment of the present invention. FIG. 10 is a block diagram showing a configuration of an optical device according to the fifth embodiment of the present invention. FIG. 11A is a block diagram showing an optical device that performs one-loop feedback control using an analog control circuit according to the prior art. FIG. 11B is a block diagram illustrating an optical device that performs one-loop feedback control using a digital control circuit according to the prior art. FIG. 12 is a block diagram illustrating an optical apparatus that performs two-loop feedback control of different monitoring targets according to the prior art.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited by embodiment described below.

(First embodiment)
First, an optical device according to a first embodiment of the present invention will be described. FIG. 1 shows an optical device according to a first embodiment.

  As shown in FIG. 1, the optical device 1 according to the first embodiment includes an optical amplifying unit 11, optical couplers 12 and 13, a PD monitor unit 14, an LD driving unit 15, and an error amplifying unit that is an analog control circuit. 16 and an LD current setting unit 17.

  In the optical device 1, the LD driving unit 15 drives the pump LD 15 a made of a semiconductor laser for outputting pumping light for exciting the optical amplification unit 11. The LD drive unit 15 controls the optical output power of the pumping light output from the pump LD 15 a based on the electrical signal supplied from the error amplification unit 16. The pump LD 15 a outputs the output excitation light to the optical coupler 13. The optical coupler 13 multiplexes the excitation light output from the LD driving unit 15 to the optical amplification unit 11. Thereby, the optical amplifying unit 11 is excited so as to amplify the input signal light with a desired gain.

  The optical amplifying unit 11 as an optical amplifying means is composed of an amplifying optical fiber to which, for example, erbium ions are added, and optically amplifies the input signal light and outputs it. The gain of the optical amplifying unit 11 responds to a change in the intensity of the pumping light input from the LD driving unit 15 with a predetermined response time constant, specifically, for example, about several ms. The wavelength of the signal light input to the optical amplifying unit 11 is a wavelength within the amplification band of the optical amplifying unit 11, and is, for example, 1530 to 1620 nm. The optical coupler 12 outputs the signal light input from the optical amplifying unit 11 in a predetermined direction (left side in FIG. 1), and part of the input signal light has a branching ratio of about 1/10 to 1/100. Then, the data is branched and supplied to the PD monitor unit 14.

  The PD monitor unit 14 includes a PD 14a that converts an optical signal into an electrical signal. When the PD 14a receives a part of the signal light branched by the optical coupler 12, it converts it into an electric signal and amplifies it. The PD monitor unit 14 outputs a PD monitor signal corresponding to the detected value of the intensity of the signal light from the optical coupler 12 input to the PD 14a.

  The PD monitor signal output from the PD monitor unit 14 is supplied to the error amplification unit 16 and to the LD current setting unit 17. The LD current setting unit 17 sets an LD current value to be supplied to the pump LD 15a according to the supplied PD monitor signal, and outputs an LD current setting signal corresponding to the LD current value. The LD current setting unit 17 supplies the output LD current setting signal to the error amplification unit 16. The error amplifying unit 16 amplifies the difference between the PD monitor signal supplied from the PD monitor unit 14 and the LD current setting signal supplied from the LD current setting unit 17 to generate an LD signal as an electric signal. 15 is supplied.

  In the first embodiment, the PD monitor unit 14, the error amplification unit 16, and the LD current setting unit 17 constitute a control circuit. In addition, the optical amplification unit 11 and the LD driving unit 15 constitute an optical module controlled by a control circuit.

In the optical device 1 which is an optical module with a control circuit configured as described above, the PD monitor unit 14, the error amplifying unit 16, and the LD driving unit 15 perform a time constant T with respect to the response time constant of the optical amplifying unit 11. A high-speed feedback loop is configured as a first feedback loop in which ₁ is relatively small. Further, in the optical device 1, the PD monitor unit 14, the LD current setting unit 17, the error amplification unit 16, and the LD driving unit 15 serve as a second feedback loop having a time constant T ₂ that is larger than the time constant T _1. The slow feedback loop is configured. Here, the time constant T ₁ of the high-speed feedback loop corresponds to the input light fluctuation caused by, for example, fiber handling. In this case, the time constant T ₁ is 1 with respect to the transient time (for example, 1 ms) of the input light fluctuation. / 10 or less is desirable. Further, it is desirable that the low-speed feedback loop time constant T ₂ is about several ms which is a small value of 1/10 or less with respect to, for example, several hundred ms which is a time constant when changing the set value.

That is, in the optical device 1, a plurality of feedback loops are configured by the combination of the control circuit and the optical module, and specifically, two feedback loops are configured. At constant T ₁ time of the first feedback loop time constant T ₂ Metropolitan second feedback loop, T ₁ <T ₂ is configured to stand.

  The inventor of the present invention has the optical device 1 configured as described above to perform control by two feedback loops having different time constants for one monitoring target, and one conventional one monitoring target. The input optical power and the output optical power were measured using an optical device that performs control using two feedback loops. FIG. 2A is an example of a measurement waveform of the input optical power of signal light input during fiber handling. Similarly, FIGS. 4A and 5A are examples of measurement waveforms of the input optical power of the signal light input to the optical device during fiber handling. The fiber handling means handling an optical fiber connected to the input side of the optical device. Then, it is assumed that the input optical power of the signal light input to the optical device by this fiber handling varies as shown in FIGS. 2A, 4A, and 5A.

2B and FIG. 3 show the case of the high-speed feedback loop in which the time constant T ₂ of the low-speed feedback loop in the first embodiment is fixed and the signal light of the input optical power shown in FIG. 2A is input. It is a measurement waveform of the output light power output from the optical device 1 when the constant T ₁ is changed. 4B and 5B are measurement waveforms of the output light power when the signal light in which the input fluctuation as shown in FIGS. 4A and 5A occurs is input to the conventional optical device, respectively.

As shown in FIG. 2A, the input optical power of the signal light input to the optical device 1 fluctuates by about 5.5 dB due to, for example, fiber handling. On the other hand, FIG. 2B shows that the output light power from the optical device 1 is suppressed to an output fluctuation of about 2.0 dB from −1.3 dB to 0.7 dB. In this case, the ratio (T ₂ / T ₁ ) of the time constants of the two feedback loops is less than 10 times. Further, from FIG. 3, when the time constant T ₁ of the high-speed feedback loop is made smaller than in the case of FIG. 2B, the output light power from the optical device 1 is suppressed to almost 0 dB, and the change in the light output during fiber handling is reduced. It turns out that it is suppressed further. In this case, the time constant ratio (T ₂ / T ₁ ) is 10 times or more. Here, the ratio of the time constants of the two feedback loops (T ₂ / T ₁ ) does not directly affect the suppression of output fluctuations, but if this ratio is small, there is a concern about control instability such as oscillation. In order to stabilize the control, it is desirable to increase the time constant ratio.

  On the other hand, as a comparative example, a case will be described in which the input optical power of signal light input to a conventional optical device varies as shown in FIGS. 4A and 5A, for example, during fiber handling. In this case, if the time constant of the feedback loop is increased in order to ensure the stability at the time of switching the setting value of the output light level, the output light power is output as it is as shown in FIGS. 4B and 5B. Reflected in fluctuations. As described above, in the conventional optical device, when it is attempted to ensure the stability at the time of switching the set value of the output light level, it is understood that the output fluctuation with respect to the input fluctuation due to, for example, fiber handling is hardly suppressed. That is, from the comparison between FIG. 4A and FIG. 4B and the comparison between FIG. 5A and FIG. 5B, in the conventional optical apparatus in which control is performed by one feedback loop for one monitoring target, It can be seen that the output fluctuation of the output optical power is hardly suppressed.

  Further, the inventor has confirmed the signal light power output from the optical device when the set value of the output light level is switched. 6A is a measurement waveform of the output optical power of the optical device 1 according to the first embodiment, and FIG. 6B is a feedback loop of the conventional optical device in order to suppress the output variation with respect to the input variation due to fiber handling, for example. It is a measurement waveform of output light power when the time constant is reduced.

As shown in FIG. 6A, when the set value of the output light power is increased from 7 dBm to 10 dBm, for example, based on the trigger signal at time T ₀ , as shown in FIG. It can be seen that there is a problem that the output optical power varies greatly. On the other hand, FIG. 6A shows that according to the optical device 1 according to the first embodiment, the output light power can be changed smoothly by suppressing overshoot without greatly changing the output light power.

(Example)
Next, embodiments in which the ratio between the time constant T ₁ of the high-speed feedback loop and the time constant T ₂ of the low-speed feedback loop is variously changed using the optical device 1 configured as described above will be described.

(First embodiment)
First, as a first embodiment, the time constant T ₁ of the high-speed feedback loop is set to 22 μs, and the time constant T ₂ of the low-speed feedback loop is set to 1000 μs (= 1.0 ms). At this time, the ratio of the time constants (T ₂ / T ₁ ) between the fast feedback loop and the slow feedback loop is 45.5. Under these conditions, the present inventor confirmed the control stability and output fluctuation in the optical device 1, and found that the output fluctuation with respect to the transient fluctuation of the input light while ensuring the control stability at the time of switching the set value of the output light level. As shown in FIG. 3, it was confirmed that it can be suppressed.

(Second embodiment)
As a second embodiment, the time constant T ₁ of the fast feedback loop is 2.2 μs, and the time constant T ₂ of the slow feedback loop is 1000 μs. At this time, the ratio of the time constants of the two feedback loops is T ₂ / T ₁ = 454.5. Under these conditions, the present inventor confirmed the control stability and the output fluctuation. FIG. 3 also shows the output fluctuation with respect to the transient fluctuation of the input light while ensuring the control stability at the time of switching the set value of the output light level. It was confirmed that it can be suppressed as shown.

(Third embodiment)
As a third embodiment, the time constant T ₁ of the high-speed feedback loop is 220 μs, and the time constant T ₂ of the low-speed feedback loop is 1000 μs. At this time, the ratio of the time constants of the two feedback loops is T ₂ / T ₁ = 4.5. Under this condition, the present inventor confirmed the control stability and the output fluctuation, and the control stability was slightly worse than in the first and second embodiments and had a slight fluctuation. It was confirmed that there was no problem. Further, although the output fluctuation is slightly larger than that of the first and second embodiments, it has been confirmed that the output fluctuation is smaller than that of the prior art.

(Fourth embodiment)
As a fourth embodiment, the time constant T ₁ of the fast feedback loop is 123.2 μs, and the time constant T ₂ of the slow feedback loop is 1000 μs. At this time, the ratio of the time constants of the two feedback loops is T ₂ / T ₁ = 8.1. Under this condition, the present inventor confirmed the control stability and the output fluctuation, and the control stability was slightly worse than in the first and second embodiments and had a slight fluctuation. It was confirmed that there was no problem. Further, although the output fluctuation is slightly larger than that of the first and second embodiments, it has been confirmed that the output fluctuation is smaller than that of the prior art.

(Fifth embodiment)
In the fifth embodiment, the time constant T ₁ of the high-speed feedback loop is 66 μs, and the time constant T ₂ of the low-speed feedback loop is 1000 μs. At this time, the ratio of the time constants of the two feedback loops is T ₂ / T ₁ = 15.2. Under this condition, the present inventor confirmed the control stability and the output fluctuation, and the control stability was slightly worse than in the first and second embodiments and had a slight fluctuation. It was confirmed that there was no problem. On the other hand, it was confirmed that the output fluctuation can be suppressed similarly to the first and second embodiments.

(Sixth embodiment)
In the sixth embodiment, the time constant T ₁ of the high-speed feedback loop is 44 μs, and the time constant T ₂ of the low-speed feedback loop is 1000 μs. At this time, the ratio of the time constants of the two feedback loops is T ₂ / T ₁ = 22.7. Under this condition, the present inventor confirmed the control stability and the output fluctuation, and it was confirmed that the output fluctuation can be suppressed similarly to the first and second embodiments while ensuring the control stability.

The inventor has further studied based on the results of the first to sixth embodiments. As a result, regarding the output fluctuation, when the time constant T ₂ is 1000 μs (1 ms), the time constant T ₁ of the high-speed feedback loop is reduced, and the time constant ratio T ₂ / T _{1 of the two} feedback loops is 15 It was confirmed that the output fluctuation was within the range of ± 1 dB when. According to the knowledge of the present inventor, output fluctuation due to a transient phenomenon such as fiber handling can be suppressed by appropriately setting the time constant T ₁ of the high-speed feedback loop. As a result of various studies by the inventor, when the time constant T ₂ of the low-speed feedback loop is fixed, if the ratio of the time constant is small, control instability such as oscillation is a concern. For this reason, it is desirable to increase the ratio. As a result, if the ratio T ₂ / T ₁ of the time constant is set to 10.0 or more as in the case of setting in the embodiment, control instability such as oscillation is suppressed. It was confirmed. Therefore, it was confirmed from the examples that the time constant T ₂ of the low-speed feedback loop is preferably 10 times or more the time constant T ₁ of the high-speed feedback loop.

  According to the above-described first embodiment of the present invention, the input light level and the output light level are controlled using the control circuit that performs feedback control for controlling the pumping light source by monitoring the input light power and the output light power. The plurality of feedback loops are controlled according to the characteristics, and in these time constants, at least one first feedback loop of the plurality of feedback loops is a high-speed feedback loop having a relatively small time constant, and the other at least one second By making the feedback loop a low-speed feedback loop with a time constant larger than the time constant of the high-speed feedback loop, fluctuations in the output light level due to transient response can be suppressed, and when the output light level setting value is switched. It is possible to ensure the stability of

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 7 is a block diagram showing an optical device 2 according to the second embodiment of the present invention.

  As shown in FIG. 7, the optical device 2 according to the second embodiment includes an optical amplification unit 21, optical couplers 22 and 23, a PD monitor unit 24 including a PD 24a, and an LD drive unit 25 including a pump LD 25a. And a digital control unit 26 including a digital control circuit including a CPU 26a, a memory 26b, and an LD current setting unit 26c.

  Unlike the optical device 1 of the first embodiment, the optical device 2 includes a digital control unit 26 as a control circuit instead of an analog control circuit. The CPU 26a and the memory 26b of the digital control unit 26 are processing means for performing digital arithmetic processing. In the digital control unit 26, an analog signal supplied from the outside is converted into a digital signal, and the CPU 26a performs arithmetic processing. In the digital control unit 26, the LD current setting unit 26c performs the same processing as the LD current setting unit 17 of the first embodiment, calculates and generates an LD current set value, and sets the LD current set value of the digital signal. Is converted into an analog signal and supplied to the LD drive unit 25.

In addition, the digital control unit 26 stores, in the memory 26b, monitor values and control value differences that can change depending on the temperature characteristics of the components of the optical device 2 by the CPU 26a and the memory 26b. Further, the digital control unit 26 is configured such that the time constants T ₁ and T ₂ of the feedback loop can be set programmably by the CPU 26a and the memory 26b. Thus, the digital control unit 26 controls a relatively small fast feedback loop constants T ₁ when the response time constant of the optical amplifier unit 21, when the slow feedback loop constant T ₁ is greater than the time constant T ₂ To do. Then, the digital control unit 26 performs control so that T ₁ <T ₂ is satisfied in the time constants T ₁ and T ₂ of a plurality of, specifically two feedback loops.

  In addition, the optical amplifier 21, optical couplers 22, 23, PD 24a, PD monitor 24, pump LD 25a, and LD driver 25, which are other configurations, are the same as the corresponding elements in the first embodiment, and thus will be described. Is omitted. In the second embodiment, the optical amplifier 21 and the LD driver 25 constitute an optical module, and the PD monitor 24 and the digital controller 26 constitute a control circuit.

According to the second embodiment described above, the same effects as those of the first embodiment can be obtained, and a digital control circuit is employed instead of the analog control circuit, so that the first embodiment can be obtained. Thus, it is possible to ensure the stability of the output optical power including temperature correction, which is difficult to cope with only the configuration of the analog control circuit as described above. Further, the digital control unit 26 stores the difference between the monitor value and the control value that can change depending on the temperature characteristics of the components of the optical device 2 in the memory 26b, thereby performing correction according to the ambient temperature. It becomes possible. Further, since the time constants T ₁ and T ₂ of the plurality of feedback loops can be set in a programmable manner, even when the time constant is changed, it can be easily handled without changing the components.

(Third embodiment)
Next, a third embodiment of the present invention will be described. FIG. 8 is a block diagram showing an optical apparatus 3 according to the third embodiment of the present invention.

  As shown in FIG. 8, the optical device 3 according to the third embodiment includes an optical amplifying unit 31, optical couplers 32 and 33, a PD monitor unit 34 including a PD 34a, and an LD driving unit 35 including a pump LD 35a. . The optical device 3 includes a digital control unit 36 including a CPU 36a as a digital control circuit, a memory 36b, and an LD current setting unit 36c, and an error amplification unit 37 as an analog control circuit.

In the optical device 3, the PD monitor unit 34, the error amplification unit 37, and the LD driving unit 35 constitute a high-speed feedback loop having a relatively small time constant T ₁ with respect to the response time constant of the optical amplification unit 31. Yes. In the optical device 3, PD monitor section 34, the digital control unit 36, by the error amplifying section 37 and the LD driving unit 35, the slow feedback loop constant T ₂ time is greater than the constant T ₁ is configured Yes. In other words, the optical apparatus 1 has a plurality of, specifically two feedback loops, and is configured such that T ₁ <T ₂ holds in the time constants T ₁ and T ₂ of these feedback loops. Yes.

  Further, the optical amplifying unit 31, the optical couplers 32 and 33, the PD 34a, the PD monitor unit 34, the pump LD 35a, the LD driving unit 35, and the error amplifying unit 37 are the same as the corresponding elements in the first embodiment, and therefore will be described. Is omitted. The configuration of the digital control unit 36 is the same as that of the digital control unit 26 of the second embodiment.

  In general, when digital control is used for high-speed control, power consumption increases and the cost required for electronic components increases, and in order to ensure the stability of output optical power including temperature correction, high-speed control is not always necessary. Since control is not necessary, it is preferable to employ an analog control circuit for high-speed control. Therefore, the optical device 3 according to the third embodiment employs a configuration in which only the LD current setting unit 17 including the analog circuit according to the first embodiment is replaced with a digital control unit 36 including an LD current setting unit 36c. To do. Since other configurations are the same as those in the first and second embodiments, description thereof is omitted.

According to the third embodiment described above, two feedback loops are provided for the optical amplifying unit 31, and T ₁ <T ₂ is established in the time constants T ₁ and T ₂ of the feedback loops. By configuring, the same effects as those of the first and second embodiments can be obtained. Further, in the third embodiment, a high speed feedback loop having a small time constant T ₁ is constituted by an analog control circuit, and a low speed feedback loop having a time constant T ₂ larger than the time constant T ₁ is constituted by a digital control circuit. Yes. As a result, the optical device 3 can ensure the stability of the output light power including temperature correction, and the high-speed feedback loop that requires relatively high-speed control is performed by a digital control circuit equipped with an FPGA or DSP. In comparison, cost reduction and power consumption can be realized.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. FIG. 9 is a block diagram showing an optical device 4 according to the fourth embodiment of the present invention.

  As shown in FIG. 9, the optical device 4 according to the fourth embodiment is provided with a VOA drive unit 44 including a VOA (Variable Optical Attenuator) 44a inserted into an optical fiber 41 that transmits an optical signal. The optical device 4 further includes an optical coupler 42, a PD monitor unit 45 including a PD 45a, a PD monitor unit 46 including a PD 46a, a VOA target value setting unit 47, and an error amplifying unit 48.

  In the optical device 4, the VOA driving unit 44 attenuates the intensity of the input signal light and outputs it. The VOA 44a is of a Mach-Zehnder type, for example, and changes the attenuation of the signal light by changing the temperature of the heater provided therein. Further, the VOA 44a responds with a predetermined response time constant with respect to a change in the driving voltage of the heater. The wavelength of the signal light input to the VOA 44a is 1530 to 1620 nm, for example.

  The optical coupler 42, the PD monitor unit 45 including the PD 45a, and the error amplifying unit 48 are the same as the corresponding elements in the first and third embodiments, and thus description thereof is omitted.

  The PD monitor signal output from the PD monitor unit 45 is supplied to the error amplification unit 48 and also to the VOA target value setting unit 47. On the other hand, the optical device 4 includes an optical coupler 43 on the signal light input side with respect to the VOA drive unit 44. The optical coupler 43 branches the input signal light at a branching ratio of 1/10 to 1/100, for example, and outputs the branched signal light to the PD 46a of the PD monitor unit 46. The PD monitor unit 46 outputs a PD monitor signal corresponding to the input optical power and supplies it to the VOA target value setting unit 47. Thereby, the optical device 4 monitors the input light level and the output light level.

  Then, the VOA target value setting unit 47 sets a VOA target value for performing optical loss constant control that makes the optical loss constant according to the supplied PD monitor signal, and outputs a VOA target value setting signal. To do. The VOA target value setting signal output from the VOA target value setting unit 47 is supplied to the error amplification unit 48. The error amplifying unit 48 amplifies the difference between the PD monitor signal supplied from the PD monitor unit 45 and the VOA target value setting signal supplied from the VOA target value setting unit 47 and outputs the amplified signal as an electric signal. And supplied to the VOA driving unit 44. The VOA driving unit 44 controls the attenuation amount of the VOA 44a based on the electric signal supplied from the error amplifying unit 48.

  In the fourth embodiment, a control circuit is configured by the PD monitor unit 45, the VOA target value setting unit 47, and the error amplifying unit 48, and controls the VOA driving unit 44 configuring the optical module.

Then, the optical device 4, the PD monitor unit 45 and the error amplifier 48, the constant T ₁ is relatively small fast feedback loop is constituted when the response time constant of VOA44a. In the optical device 4, the PD monitor unit 45, the VOA target value setting unit 47, and the error amplification unit 48 constitute a low-speed feedback loop having a time constant T ₂ that is larger than the time constant T ₁ . In other words, the optical device 4 has a plurality of, specifically two, feedback loops for the VOA 44a, and T ₁ <T ₂ is established in the time constants T ₁ and T ₂ of these feedback loops. Yes.

  In the fourth embodiment described above, the control of a plurality of feedback loops having different time constants applied to the optical amplifier in the first embodiment is applied to the VOA 44a to monitor the input light level and the output light level. However, the optical loss constant control is performed so that the optical loss is constant, and a high-speed feedback loop for suppressing transient fluctuations and a low-speed feedback loop for controlling the optical loss constant are provided. Therefore, the same effect as that of the first embodiment in which a plurality of feedback loops are applied to the control of the optical amplifier can be obtained.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. FIG. 10 is a block diagram showing an optical device 2 according to the fifth embodiment of the present invention.

  As shown in FIG. 10, the optical device 5 according to the fifth embodiment includes an optical amplifying unit 51, optical couplers 52, 53, and 54, a PD monitor unit 55 having a PD 55a, an LD driving unit 56 having a pump LD 56a, It has a PD monitor unit 57 having a PD 57a, an error amplifying unit 58 and an LD current setting unit 59 which are analog circuits.

  Unlike the optical device 1 of the first embodiment, the optical device 5 further includes an optical coupler 54 that branches input signal light, and a PD monitor unit 57 that includes a PD 57a. The input signal light is branched by the optical coupler 54 at a branching ratio of 1/10 to 1/100, for example, and input to the PD 57a of the PD monitor unit 57. The PD monitor unit 57 outputs a PD monitor signal corresponding to the intensity of the signal light input to the PD 57 a and supplies the PD monitor signal to the LD current setting unit 59.

  The LD current setting unit 59 is supplied with a PD monitor signal corresponding to the signal light output from the PD monitor unit 55 and a PD monitor signal corresponding to the signal light input from the PD monitor unit 57. In response to these two PD monitor signals, the LD current setting unit 59 sets the current value of the current supplied to the pump LD 56a so that the amplification gain in the optical amplification unit 51 is constant, and sets the LD current. Output a signal. The LD current setting unit 59 supplies the output LD current setting signal to the error amplification unit 59.

  In addition, the optical amplifier 51, the optical couplers 52 and 53, the PD 55a, the PD monitor 55, the pump LD 56a, the LD driver 56, the error amplifier 58, and the high-speed feedback loop and the low-speed feedback loop, which are other configurations. Each of them is the same as the corresponding element in the first embodiment, and thus description thereof is omitted. In the fifth embodiment, an optical module is configured by the optical amplifying unit 51 and the LD driving unit 56. The PD monitor units 55 and 57, the error amplification unit 58, and the LD current setting unit 59 constitute a control circuit.

According to the fifth embodiment described above, the level of the input signal light and the level of the output signal light are monitored, and the optical gain constant control is performed so as to make the gain constant. A fast feedback loop having a relatively small time constant T ₁ for suppressing general fluctuations and a slow feedback loop having a time constant T ₂ larger than the time constant T ₁ , and the optical device 5 is similar to the optical device 1. By having the configuration, it is possible to obtain the same effect as the light output constant control in the first embodiment.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention is possible. For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as necessary.

  For example, in the above-described fourth embodiment, it is possible to adopt a configuration that does not include the PD monitor unit 46 including the optical coupler 43 and the PD 46a as the optical device 4.

  Further, for example, in the above-described embodiment, the configuration including the most preferable two feedback loops is employed in the optical device, but a configuration including three or more feedback loops may be employed.

  Further, it is possible to configure three or more feedback loops without making the targets to be monitored the same. When this configuration is applied to the first embodiment, for example, the first feedback loop monitors the excitation current with a time constant of several tens (ns) by an ACC circuit or the like. Further, the second feedback loop is used as a high-speed feedback loop, and the output of the optical amplifying unit, for example, is monitored with an analog ALC circuit or the like with a time constant of several tens (μs). Further, for example, the output of the optical amplifying unit is monitored by a digital ALC circuit or the like with a time constant of several tens (ms) using the third feedback loop as a low-speed feedback loop.

1, 2, 3, 4, 5 Optical device 11, 21, 31, 51 Optical amplification unit 12, 13, 22, 23, 32, 33, 42, 43, 52, 53, 54 Optical coupler 14, 24, 34, 45, 46, 55, 57 PD monitor unit 14a, 24a, 34a, 45a, 46a, 55a, 57a PD
15, 25, 35, 56 LD driver 15a, 25a, 35a, 56a Pump LD
16, 37, 48, 58 Error amplification unit 17, 26c, 36c, 59 LD current setting unit 26, 36 Digital control unit 26a, 36a CPU
26b, 36b Memory 41 Optical fiber 44 VOA drive unit 47 VOA target value setting unit

Claims (11)

In an optical module control method for detecting optical output power in an optical module having a predetermined response time constant, and feedback controlling the optical output of the optical module by a control circuit according to the detected optical output power.
The control circuit has a plurality of feedback loops including a first feedback loop and a second feedback loop, and the time constant of the first feedback loop is made less than the time constant of the second feedback loop. An optical module control method.   2. The method of controlling an optical module according to claim 1, wherein the time constant of the second feedback loop is 10 times or more the time constant of the first feedback loop.   The time constant of the first feedback loop is set to a time constant capable of suppressing the fluctuation of the output optical power with respect to the transient fluctuation of the input optical power input to the optical module, and the time constant of the second feedback loop is set. 3. The method of controlling an optical module according to claim 1, wherein the time constant is set to a time constant capable of stabilizing the output optical power when the set value of the output optical power is switched.   4. The optical module control method according to claim 1, wherein the first feedback loop is configured by an analog control circuit, and the second feedback loop is configured by a digital control circuit. 5. .   5. The optical module control method according to claim 1, wherein the optical module is an optical amplifier.   The optical module control method according to claim 1, wherein the optical module is an optical variable attenuator. In an optical apparatus comprising: an optical module having a predetermined response time constant; and a control circuit that detects optical output power in the optical module and feedback-controls the optical output of the optical module according to the optical output power.
The control circuit has a plurality of feedback loops including a first feedback loop and a second feedback loop, and the time constant of the first feedback loop is less than the time constant of the second feedback loop. An optical device.   The optical apparatus according to claim 7, wherein a time constant of the second feedback loop is 10 times or more of a time constant of the first feedback loop.   9. The optical apparatus according to claim 7, wherein the first feedback loop is composed of an analog control circuit, and the second feedback loop is composed of a digital control circuit.   The optical apparatus according to claim 7, wherein the optical module is an optical amplifier.   The optical device according to claim 7, wherein the optical module is an optical variable attenuator.

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