JP4180595B2 - Wavelength multiplexed light control device - Google Patents

Description

  The present invention relates to a wavelength multiplexed light control apparatus, and more particularly to a wavelength multiplexed light control apparatus that controls the intensity of wavelength multiplexed light based on the maximum peak value of wavelength multiplexed light.

In recent years, with the progress of multimedia networks, information demand has increased dramatically, and there is a need for higher capacity and flexible network formation in trunk optical transmission systems where information capacity is concentrated. At present, the wavelength division multiplexing (WDM) transmission system is the most effective means for meeting such system demand, and commercialization has already been promoted mainly in North America. In such a WDM transmission system, it is important to manage the optical level of each channel in the transmission path, and the quality of management greatly affects the operating state of functional devices such as optical amplifiers, thereby greatly changing the transmission quality. To do. For this reason, in the WDM transmission system, it is necessary to manage each wavelength level, S / N, etc. at all relay stages.
However, it is not appropriate to install level detection devices and level control devices for each wavelength in all relay stages from the standpoint of reducing the cost of the optical transmission system, etc. Multiple light detection and control functions are required. From this viewpoint, various countermeasures have been proposed.

  FIG. 17 shows an example of a conventional wavelength-division-multiplexed light detector, which is equipped with a simple optical spectrum monitor, and is reported in a paper by K. Otsuka et al. (ECOC'97, Tu3, p147) and the like. It is an example. The wavelength multiplexed light emitted from the fiber 101 is wavelength-separated by the diffraction grating 102 and incident on the photodiode array 103, and the level of each wavelength is detected by each photodiode. The minimum number of photodiodes necessary for section monitoring This is a method for detecting the level of each wavelength.

FIG. 18 shows a second example of a conventional wavelength multiplexed light detection and control device, which is described in a paper by K. Suzuki et al. (IEEE Photon. Tech. Lett., Vol. 10, p734, 1998). It is an example. In this wavelength multiplexed light detection and control apparatus, first and second optical fiber amplifiers 110 and 120 with constant optical gain control are connected in cascade, an optical attenuator 130 is provided between them, and a second optical fiber amplifier is provided. The feedback circuit 140 is provided so that the intensity of the output light becomes constant.
In the first and second optical fiber amplifiers 110 and 120, 111 and 121 are optical isolators, 112 and 122 are rare earth element-doped fibers that amplify wavelength-multiplexed light, for example, erbium-doped fibers, and 113 and 123 have wavelengths longer than signal light. A laser diode (pumping light source) that generates short and high energy pumping light and leads it to an erbium-doped fiber, 114 and 124 are optical splitters, and 115 and 125 are light receiving units that detect the power of wavelength multiplexed light output from each optical fiber amplifier. Optical devices (photodiodes) 116 and 126 are optical detectors (photodiodes) for detecting the power of wavelength multiplexed light input to each optical fiber amplifier, and 117 and 127 are power ratios of input light and output light to each optical fiber amplifier (light). (Gain) is a set gain, and pumping light sources 113 and 123 of each optical fiber amplifier are used. An optical gain control unit for feedback signal input.

In the feedback circuit 140, 141 is a wavelength multiplexer / demultiplexer that separates and outputs the wavelength multiplexed light output from the second optical fiber amplifier for each wavelength, and 142 _{1 to} 142n are the intensities of the wavelengths λ _{1 to} λn ( 143 is a maximum value detecting unit that detects the maximum value of each wavelength level, and 144 is a light output constant that inputs a feedback signal to the optical attenuator 130 so that the maximum value becomes a set value. It is a control unit, and the optical attenuator 130 performs optical level control based on the feedback signal.
In the second conventional example, high output can be obtained by cascading optical fiber amplifiers. In the optical fiber amplifier, the gain varies depending on the wavelength, but the gain of each wavelength can be made uniform by performing constant gain control (the wavelength dependence of the gain can be made constant). Also, since the gain of each wavelength can be made uniform, the level of each wavelength can be made substantially uniform. Therefore, the wavelength at which the power is maximized is detected and controlled so that the maximum value becomes the set value. Constant power control is possible. That is, the output light power can be controlled constant by controlling only one wave with the maximum power regardless of the number of channels.

  The second conventional example is similar to the first conventional example in that the level is detected for each wavelength. However, in the second conventional example, (1) wavelength multiplexed light is separated for each wavelength by using a wavelength multiplexer / demultiplexer such as an arrayed waveguide type (AWG) with the wavelength multiplexed light confined in the fiber. , (2) After detecting the power for each channel, calculate the maximum value of these and feedback control to the optical attenuator to control the power per channel constant. (3) Number of wavelength branches of the wavelength multiplexer / demultiplexer This is different from the first conventional example in that the number of received light wavelengths is limited due to the above limitation.

FIG. 19 shows a third example of a conventional wavelength multiplexed light detection and control device, which is described in a report by Saeki et al. (NEC Technical Bulletin vol.51, no.4, p45, 1998). In this wavelength multiplexed light detection and control device, the optical circulator 150 inputs the incident wavelength multiplexed light to the wavelength multiplexer / demultiplexer 160, and the wavelength multiplexer / demultiplexer 160 converts the wavelength multiplexed light into the wavelength light λ ₁ to λ ₁ of each channel. Separate into λn. The separated wavelength light λ _{1 to} λ n of each channel is input to the photodiodes 174 ₁ to 174 n via the variable optical attenuators 171 _{1 to} 171 n, total reflection mirrors 172 _{1 to} 172 n, and optical branching couplers 173 ₁ to 173 n. Photodiode 174 ₁ ~174n photoelectrically converts the respective wavelength light input and fed back to the variable optical attenuator 171 ₁ ~171n. Thereby, the level of each wavelength of each channel is individually adjusted to a certain level.

The wavelength division multiplexing photodetection device of the first conventional example shown in FIG. 17 is large in size and has an optical system. For this reason, it is not suitable for a wavelength multiplexed light detection / control device required in all the relay stages.
The wavelength-division multiplexed light detection / control apparatus of the second conventional example of FIG. 18 requires an expensive wavelength multiplexer / demultiplexer, and there is a limit to the number of channels to be wavelength-divided by the wavelength multiplexer / demultiplexer. However, there is a problem that it cannot flexibly cope with changes in the number of channels and wavelength.
The wavelength-division-multiplexed light detection / control apparatus of the third conventional example in FIG. 19 can perform high-precision control because the level is individually adjusted for each channel. However, an expensive wavelength multiplexer / demultiplexer is required, and the channel Each time, an optical attenuator, a total reflection mirror, an optical branching device, a photodiode, etc. are required, and the configuration increases. In addition, there is a problem that the number of channels and wavelength change cannot be flexibly handled.

As described above, various methods and configurations have been proposed as wavelength division multiplexed light detection / control devices, but each has its own problems. Enumerating functions required as a wavelength multiplexed light detection and control device,
・ Detection and constant control of optical power per wave of wavelength light allocated to each channel (or detection of its maximum value and its constant control) are possible.
・ Understanding the number of multiple wavelengths
-A configuration that does not depend on the channel wavelength or the number of multiplexed wavelengths-A low cost, small size, simple configuration, etc. Conventional devices satisfy some of these, but not all.
As described above, the object of the present invention is to provide a simple configuration, without the need for an expensive wavelength multiplexer / demultiplexer, and without depending on the channel wavelength or the number of multiplexed wavelengths, and outputting by controlling one wave of maximum power. It is an object of the present invention to provide a wavelength-multiplexed light control apparatus that can perform constant power control of light and can grasp the number of multiplexed wavelengths.

The first wavelength multiplexing optical control apparatus of the present invention includes an optical fiber amplifier that amplifies the wavelength multiplexed light that propagates, an optical branching means that branches a part of the wavelength multiplexed light output from the optical fiber amplifier, A wavelength tunable optical filter that selectively outputs each wavelength light, a photoelectric conversion means that photoelectrically converts light output from the wavelength tunable optical filter, a peak detection means that detects a maximum peak value of an electrical signal output from the photoelectric conversion means, Power detection means for detecting the total power of the wavelength multiplexed light output from the optical fiber amplifier, if the maximum peak value protrudes, a power constant control is performed so that the total power becomes a set power, and a feedback signal is generated. If the maximum peak value does not protrude, constant control of the maximum peak value is performed to generate a feedback signal , and the feedback signal is used as a pumping light source of the optical fiber amplifier. Feedback means for input is provided.

The second wavelength multiplexing optical control apparatus of the present invention includes an optical fiber amplifier that amplifies the wavelength multiplexed light that propagates, an optical branching means that branches a part of the wavelength multiplexed light output from the optical fiber amplifier, A wavelength tunable optical filter that selectively outputs each wavelength light, a photoelectric conversion means that photoelectrically converts light output from the wavelength tunable optical filter, a peak detection means that detects a maximum peak value of an electrical signal output from the photoelectric conversion means, Means for detecting the optical gain, which is the power ratio of the input light to the optical fiber amplifier and the output light from the optical fiber amplifier; if the maximum peak value protrudes, a constant control of the gain is performed to generate a feedback signal. If the maximum peak value does not protrude, a feedback signal is generated by performing constant control of the maximum peak value , and the feedback signal is input to the pumping light source of the optical fiber amplifier. Means.

The third wavelength division multiplexing optical control apparatus of the present invention is a first optical fiber amplifier that amplifies wavelength multiplexed light of the number of multiplexed channels Nch, and a power ratio between input light and output light to the first optical fiber amplifier. First feedback means for inputting a feedback signal to the pumping light source of the first optical fiber amplifier so that a certain optical gain becomes a set gain, and light for controlling the optical level of wavelength multiplexed light output from the first optical fiber amplifier The level control means, the second optical fiber amplifier that amplifies the wavelength multiplexed light output from the optical level control means, and the optical gain that is the power ratio between the input light and the output light to the second optical fiber amplifier becomes the set gain. A second feedback means for inputting a feedback signal to the pumping light source of the second optical fiber amplifier, an optical branching means for branching a part of the wavelength multiplexed light output from the second optical fiber amplifier, and a branched wave Peak detection wavelength tunable optical filter for selectively outputting the respective wavelength light multiplexed light, photoelectric conversion means for photoelectrically converting the light output from the tunable optical filter, the maximum peak value Ppeak of the electric signal output from the photoelectric conversion means Detection means, power detection means for detecting the total power P ₀ of the wavelength multiplexed light output from the second optical fiber amplifier,
If P _0> Ppeak · Nch, enter the difference between Ppeak · Nch set power Ps to (= Ps-Ppeak · Nch) to the light level control means, if P ₀ ≦ Ppeak · Nch, and P ₀ Third feedback means is provided for inputting a difference (= Ps−P ₀ ) in the set power Ps to the light level control means, and the light level control means performs light level control based on the input signal .

According to the wavelength multiplexing light control apparatus of the present invention, even when the maximum peak value protrudes from the light level of each wavelength, the maximum value constant control can be effectively performed. In addition, by detecting the number of wavelength multiplexing based on the number of peaks of the electrical signal output from the photoelectric conversion means, and changing the set power according to the number of wavelength multiplexing, it is possible to perform a good constant light level control. Further, constant maximum value control can be effectively performed without causing excessive gain tilt.
According to the wavelength division multiplexing optical control apparatus of the present invention, the constant gain control is performed by the constant gain control unit to make the gain of each channel uniform, and thereby the maximum value constant control can be performed in a state where the wavelength light levels are substantially uniform. Therefore, the power of the output light can be controlled constant by controlling only one wave with the maximum power regardless of the number of channels, and the level of each channel can be made uniform.
According to the wavelength division multiplexing optical control apparatus of the present invention , it is possible to control the power of the output light constant by controlling only one wave with the maximum power regardless of the number of channels, and to make the level of each channel uniform, Output and other channels are possible.

  Optical level control means for controlling the optical level of the wavelength multiplexed light propagating is provided, a part of the wavelength multiplexed light output from the optical level control means is branched, and each wavelength light included in the wavelength multiplexed light is separated by the wavelength tunable optical filter. Selectively output, photoelectrically convert each wavelength light output from the wavelength tunable optical filter by the photoelectric conversion means, and detect the maximum peak value of the electrical signal output from the photoelectric conversion means by the peak value detection means, the maximum peak value The feedback signal is input to the optical level control hand so that becomes the set value.

(A) Wavelength multiplexed light detection apparatus (a) First embodiment FIG. 1 is a block diagram of a first embodiment of a wavelength multiplexed light detection apparatus according to the present invention, 11 is an optical fiber that propagates wavelength multiplexed light, and 12 is a wavelength. An optical branching coupler for branching the multiplexed light, 13 is a wavelength variable optical filter with a variable center wavelength that selectively outputs each wavelength of the branched wavelength multiplexed light, and 14 is a photoelectric converter that photoelectrically converts the light output from the wavelength variable optical filter. A photodiode (PD) 15 as a converting means is a peak detection circuit for detecting a peak (for example, maximum peak) of an electric signal output from the photodiode.
Examples of the tunable optical filter 13 include an acousto-optic tunable optical filter, an electro-optic tunable optical filter, a thermo-optic tunable optical filter, and a mechanical tunable optical filter. In the present invention, an acousto-optic tunable optical filter, An electro-optic tunable optical filter is optimal in terms of sweep speed and the like.

FIG. 2 is a block diagram of an acousto-optic tunable optical filter, 13a is a SAW waveguide formed on a substrate having an electro-optic effect such as LiNbO3 (lithium niobate), 13b is an interdigital transducer (IDT), 13c is a SAW clad formed to sandwich the SAW waveguide by Ti diffusion, 13d and 13e are absorbers that absorb surface acoustic waves (SAW), 13f and 13g are optical waveguides formed by Ti diffusion, 13h and 13i are cross-type polarization beam splitters (PBS) for polarization-independent operation, and are configured to sandwich two linear waveguides. Reference numeral 13j denotes a high-frequency signal applying unit that applies a high-frequency signal of 170 to 180 MHz to the interdigital electrode 13b, and a configuration in which an inductance 13j-2 for canceling the input capacitance of the interdigital electrode IDT is connected in series to the high-frequency generator 13j-1. have. When a high frequency signal is applied to the interdigital transducer 13, a surface acoustic wave SAW is generated, and this surface acoustic wave has an effect of rotating the polarized wave having a specific wavelength according to the frequency by 90 ^° . For this reason, a variable wavelength filter can be realized by providing polarization beam splitters 13h and 13i on the input side and output side for polarization separation. For example, if you enter the wavelength-multiplexed light of the TE mode as the input light to the wavelength tunable optical filter 13, only the polarized light with wavelength corresponding to the frequency of the high frequency signal applied to the interdigital electrodes 90 ⁰ rotated to the polarization of the TM mode Thus, the TM mode polarization is output from the optical waveguide 13g.

FIG. 3 shows the tuning characteristics of the wavelength tunable optical filter. The horizontal axis represents the frequency of the high-frequency signal, and the vertical axis represents the selected wavelength. The selected wavelength is shortened in inverse proportion to the frequency of the high frequency signal.
Therefore, each wavelength light contained in the input light can be selectively output sequentially by sweeping the frequency of the high frequency signal output from the high frequency signal applying unit 13j at a predetermined period.
As described above, when the wavelength multiplexed light enters the optical fiber 11, the optical branching coupler 12 branches a part of the wavelength multiplexed light and inputs it to the wavelength tunable optical filter 13. Since the wavelength tunable optical filter 13 periodically sweeps the center wavelength with a predetermined width, each wavelength light included in the wavelength multiplexed light is sequentially separated and inputted to the photodiode 14, and the photodiode 14 photoelectrically converts the input light into an electrical signal. The data is converted and input to the peak detection circuit 15.

FIG. 4 is an explanatory view of the time change of the incident spectrum of the wavelength multiplexed light and the light receiving level. Since the wavelength tunable optical filter 13 periodically sweeps the center wavelength with a predetermined width, the optical power received by the photodiode 14 shows a power change in which the wavelength axis is converted into the time axis. For example, when wavelength-multiplexed light in which wavelengths λ ₁ , λ ₂ , λ ₄ , and λ ₅ are multiplexed as shown in FIG. 4 (a) is incident, the level change after photoelectric conversion by the center wavelength reciprocal sweep is shown in FIG. ) As shown. The peak detection circuit 15 detects a peak value for the waveform of FIG. 4B, and detects the maximum peak value or each peak value and the number of peaks. The maximum peak value indicates the optical level (optical power) of the wavelength light having the maximum spectrum among the many wavelength lights included in the wavelength multiplexed light.

(B) Second Embodiment FIG. 5 is a block diagram of a second embodiment of the wavelength division multiplexing photodetection device of the present invention. The same parts as those in the first embodiment of FIG. The second embodiment is different from the first embodiment in that two or more wavelength tunable optical filters 13 _{1 to} 13n are connected in cascade, and the wavelength tunable optical filters 13 _{1 to} 13n are synchronously swept. If only one wavelength tunable optical filter is used, the wavelength width (half width) at which the peak value is halved becomes wide, and the wavelength selectivity is poor. Therefore, if a plurality of wavelength tunable optical filters 13 ₁ to 13 n are connected in cascade as in the second embodiment, wavelength light with a narrower half-value width can be output, and wavelength selectivity can be improved.

(C) Third Embodiment FIG. 6 is a block diagram of a third embodiment of the wavelength division multiplexing photodetection device of the present invention. The same reference numerals are given to the same parts as those in the first embodiment of FIG. The third embodiment is different from the first embodiment in that an optical equalization filter 16 is provided between the wavelength tunable optical filter 13 and the photodiode 14. Even if the spectrum of each wavelength is the same, the peak value of each wavelength output from the tunable optical filter 13 is different, and accurate peak detection cannot be performed. Therefore, in the third embodiment, an optical equalization filter 16 having an equalization characteristic so that the peak values of the respective wavelengths are at the same level when the input spectrum is the same is provided in the subsequent stage of the wavelength tunable optical filter 13. Thereby, peak detection and maximum peak value can be detected with high accuracy.

(B) Wavelength division multiplexed light control device (a) First embodiment FIG. 7 is a block diagram of the first embodiment of the wavelength division multiplexed light control device of the present invention, 21 is an optical fiber that propagates wavelength multiplexed light, and 22 is a wavelength. An optical branching coupler for branching the multiplexed light, 23 is a wavelength multiplexed light peak detector for detecting the peak of the wavelength multiplexed light, and 24 is a device for controlling the optical level of the output light, for example, a variable optical attenuator. As the variable optical level control device, an external optical modulator, a semiconductor optical amplifier, etc. can be used in addition to the variable optical attenuator.
The wavelength-multiplexed light peak detector 23 has the same configuration as the wavelength-multiplexed light detection device of FIG. 1, 13 is a variable wavelength optical filter with variable center wavelength that selectively outputs each wavelength light of the branched wavelength-multiplexed light, 14 Is a photodiode (PD) as photoelectric conversion means for photoelectrically converting light output from the wavelength tunable optical filter, and 15 is a peak detection circuit for detecting the maximum peak value of an electric signal output from the photodiode and inputting it to the variable optical attenuator 24. It is.

When the wavelength multiplexed light enters the optical fiber 21, the optical branching coupler 22 branches a part of the wavelength multiplexed light output from the variable optical attenuator 24 and inputs it to the wavelength tunable optical filter 13 of the wavelength multiplexed light peak detector 23. . Since the wavelength tunable optical filter 13 periodically sweeps the center wavelength with a predetermined width, each wavelength light included in the wavelength division multiplexed light is sequentially separated and inputted to the photodiode 14, and the photodiode 14 photoelectrically converts the input light into an electric signal. The data is converted and input to the peak detection circuit 15. The peak detection circuit 15 detects the maximum peak value, that is, the light level of the wavelength light having the maximum spectrum among the many wavelength lights included in the wavelength multiplexed light, and generates a feedback signal so that the maximum peak value becomes the set value. And input to the variable optical attenuator 24. For example, the difference between the detected maximum peak value and the set value is input to the variable optical attenuator 24 as a feedback signal. The variable optical attenuator 24 controls the level of output light based on the feedback signal. Thereafter, the feedback control is performed in cascade, and the maximum peak value becomes the set value.
It is also possible to provide a feedback circuit 16 that calculates the difference between the maximum peak value and the set value and inputs it to the variable optical attenuator 24 after the peak detection circuit 15.

In summary, the temporal change in the received light level corresponding to the spectrum of each wavelength light included in the wavelength multiplexed light is obtained, and the peak value of this is detected to detect the maximum channel value (maximum peak value). Feedback control to the variable light level control device.
If the gain equalization with respect to the wavelength is sufficiently performed, it is generally considered that the level error of each channel (each wavelength light) is small. Further, the maximum value of the output level per channel is mainly defined by the non-linear type of the transmission line optical fiber. Therefore, sufficient level constant control can be performed over all channels by maximum value detection / maximum value constant control as described above.
In the above, the case where the configuration of FIG. 1 is used as the wavelength multiplexed light peak detection unit 23 has been described. However, the configuration in which the wavelength variable optical filters 13 ₁ to 13 n of FIG. 5 are connected in cascade and the optical equalization filter 16 of FIG. The structure provided in the back | latter stage of the wavelength tunable optical filter 13 can also be used.

(B) Second Embodiment FIG. 8 is a block diagram of a second embodiment of the wavelength division multiplexing optical control apparatus according to the present invention. Components identical with those of the first embodiment of FIG. The second embodiment of FIG. 8 differs from the first embodiment in that an optical fiber amplifier is used instead of the variable optical attenuator as means for controlling the level of output light.
In FIG. 8, 25 and 26 are optical isolators, 27 is a wavelength multiplexing coupler that combines pumping light and signal light, 28 is an optical amplification fiber such as an erbium-doped fiber (EDF) that amplifies signal light, and 29 is signal light. This is a laser diode (pumping light source) that generates pumping wavelength light having a shorter wavelength and higher energy and inputs the light into an optical amplification fiber.

The wavelength multiplexed light (signal light) incident on the optical fiber 21 passes through the optical isolator 25, is combined with the excitation wavelength light emitted from the excitation light source 29 in the wavelength multiplexing coupler 27, and enters the optical amplification fiber 28. Amplified. The amplified wavelength multiplexed light passes through the optical isolator 26 and reaches the optical branching coupler 22. The optical branching coupler 22 branches a part of the wavelength multiplexed light and inputs it to the wavelength tunable optical filter 13 of the wavelength multiplexed light peak detector 23. Since the wavelength tunable optical filter 13 periodically sweeps the center wavelength with a predetermined width, each wavelength light included in the wavelength multiplexed light is sequentially separated and inputted to the photodiode 14, and the photodiode 14 electrically converts the power of each wavelength light. The signal is photoelectrically converted and input to the peak detection circuit 15. The peak detection circuit 15 detects the maximum peak value, that is, the light level of the wavelength light having the maximum spectrum among the many wavelength lights included in the wavelength multiplexed light, and generates a feedback signal so that the maximum peak value becomes the set value. And input to the excitation light source 29. The excitation light source 29 controls the intensity of the excitation wavelength light based on the feedback signal, and controls the light level output from the optical amplification fiber 28. Thereafter, the feedback control is performed in cascade, and the maximum peak value becomes the set value.
Note that a feedback circuit 20 that calculates the difference between the maximum peak value and the set value and inputs the difference to the excitation light source 29 can be provided after the peak detection circuit 15.

Also in the maximum value detection / maximum value constant control of the second embodiment, sufficient level constant control can be performed over all channels for the same reason as in the first embodiment. In the above, the case where the configuration of FIG. 1 is used as the wavelength multiplexed light peak detection unit 23 has been described. However, the configuration in which the wavelength variable optical filters 13 ₁ to 13 n of FIG. 5 are connected in cascade and the optical equalization filter 16 of FIG. The structure provided in the back | latter stage of the wavelength tunable optical filter 13 can also be used.

(C) Third Embodiment FIG. 9 is a block diagram of a third embodiment of the wavelength division multiplexing optical control apparatus of the present invention. The same reference numerals are given to the same parts as those of the second embodiment of FIG. The third embodiment of FIG. 9 differs from the second embodiment in that (1) a constant maximum value control system and a constant total power control system are provided as means for controlling the output light level, and (2) a maximum peak value. The maximum value constant control and the total power constant control are appropriately performed based on the difference between and the set peak value.

In the first and second embodiments, the control is based on the premise that the level error of each channel (each wavelength light) is small. However, depending on the situation, the maximum peak value (peak value of a certain wavelength light) may become too large and protrude beyond the peak value of other wavelength light. In such a case, the maximum value constant control of the first and second embodiments is dominated by the power (maximum peak value) of the protruding wavelength light, the light output cannot be made constant, and the level difference of each channel becomes large. Therefore, if the maximum peak value protrudes, the output light total power constant control is performed to reduce the level difference of each channel, and if the maximum peak value does not protrude, the maximum value constant control is performed to make the output light constant. At the same time, the level is substantially constant over all channels. That is, if the total power is P ₀ and the peak detection value is Ppeak, and the number of channels is N,
P ₀ << Ppeak · N
In this case, the total power constant control is performed to make the feedback by the total power P ₀ dominant.

  In FIG. 9, 30 is a branch coupler that further branches the wavelength multiplexed light branched by the branch coupler 22 and inputs it to the constant maximum value control system and the constant total power control system, and 31 is a photodiode that photoelectrically converts the wavelength multiplexed light into an electrical signal. , 32 detects the total power of the wavelength multiplexed light (output light) from the input electrical signal, and outputs a difference between the power detection value and the power setting value, and 33 is a control correction unit. Depending on the difference between the maximum peak (peak detection value) and the peak setting value, (1) the feedback signal so that the peak detection value becomes the peak setting value or (2) the power detection value becomes the power setting value. Is input to the excitation light source 29 of the optical fiber amplifier.

FIG. 10 shows a configuration example of the control correction unit 33, 33a is an operational amplifier that calculates and outputs the difference between the peak detection value and the peak setting value, and 33b is an operational amplifier that calculates and outputs the difference between the power detection value and the power setting value. , 33c and 33d are diodes that constitute a diode switch, and are connected to output the higher one of the two operational amplifiers.
When the peak detection value becomes considerably larger than the peak setting value, the output of the operational amplifier 33a is negative and its absolute value increases. Even if the peak detection value increases, the change in detection power is small, and the absolute value of the output of the operational amplifier 33b is small. Therefore, the output level of the operational amplifier 33b is higher than the output level of the operational amplifier 33a, and the difference between the power detection value and the power setting value is input as a feedback signal to the excitation light source 29, and the power difference becomes zero. Is done.
On the other hand, when the difference between the peak detection value and the peak setting value is small, the output level of the operational amplifier 33a becomes higher than the output level of the operational amplifier 33b, and the difference between the peak detection value and the peak setting value becomes a feedback signal. And the control is performed so that the peak detection value becomes the peak set value.

In the third embodiment, the case where the configuration of FIG. 1 is used as the wavelength multiplexed light peak detector 23 has been described. However, the configuration in which the wavelength variable optical filters 13 ₁ to 13 n of FIG. A configuration in which the optical filter 16 is provided at the subsequent stage of the wavelength tunable optical filter 13 can also be used. In the third embodiment, the number of channels N is known and the power setting value corresponding to the number of channels is fixed. However, the number of channels is detected and the power setting value is determined according to the number of detected channels. You can also.
FIG. 11 shows a modification of the third embodiment. Reference numeral 34 denotes a wavelength number counter. The number of wavelength lights included in the wavelength multiplexed light is counted by counting the peaks of the waveform as shown in FIG. To get to. Specifically, when the output signal of the photodiode 14 exceeds a predetermined threshold value, it is recognized as “1” at the TTL level and counted at the rising edge, and the count number in the period of the sweep half cycle of the wavelength tunable optical filter 13 is set to the channel. The number is input to the total power constant control unit 32 as a number.

(D) Fourth Embodiment FIG. 12 is a block diagram of a fourth embodiment of the wavelength division multiplexing optical control apparatus according to the present invention. Components identical with those of the second embodiment of FIG. The fourth embodiment of FIG. 12 differs from the second embodiment in that (1) a constant maximum value control system and a constant gain control system are provided as means for controlling the output light level, and (2) the maximum peak value is The maximum value constant control and the constant gain control are appropriately performed based on the difference from the set peak value.
In the first and second embodiments, the control is based on the premise that the level error of each channel (each wavelength light) is small. However, depending on the situation, the maximum peak value (peak value of a certain wavelength light) may become too large and protrude beyond the peak value of other wavelength light. In such a case, the maximum value constant control of the first and second embodiments is dominated by the protruding light power (maximum peak value), the light output cannot be made constant, and the level difference of each channel becomes large. Therefore, if the maximum peak value is prominent, constant gain control is performed to make the gain of each channel substantially uniform. That is, in the optical fiber amplifier, the gain changes depending on the wavelength, but the gain of each wavelength can be made uniform by making the gain constant control (the wavelength dependency of the gain is made constant). If the gain becomes uniform, the level difference between the channels becomes small, and if the maximum peak value does not protrude, the constant maximum value control is performed to make the level substantially constant over all channels. In this way, constant maximum value control can be effectively performed without causing an excessive gain tilt with respect to the wavelength by optical gain monitoring.

  In FIG. 12, reference numeral 30 denotes a branch coupler, which further branches the output light (wavelength multiplexed light) branched by the branch coupler 22 and inputs it to the maximum value constant control system and constant gain control system, and 31 denotes the branch coupler 30. The photodiode 41 photoelectrically converts the output light branched into an electrical signal, 41 is an optical branch coupler that branches the input light (wavelength multiplexed light), 42 is a photodiode that photoelectrically converts the input light branched by the branch coupler into an electrical signal, 43 A constant gain control unit that calculates output power and input power based on electrical signals output from the photodiodes 31 and 42, calculates an optical gain from the ratio thereof, and outputs a signal corresponding to the difference between the detected gain and the set gain 44 is a control correction unit, and (1) the peak detected value becomes the peak set value by the difference between the detected maximum peak (peak detected value) and the peak set value. Or (2) A feedback signal is input to the pumping light source 29 of the optical fiber amplifier so that the optical gain detection value becomes the optical gain setting value.

FIG. 13 shows a configuration example of the control correction unit 44, in which 44a is an operational amplifier that calculates and outputs the difference between the peak detection value and the peak setting value, and 44b is a calculation that outputs the difference between the optical gain detection value and the optical gain setting value. The operational amplifiers 44c and 44d that constitute the diode switch are diodes, and are connected to output the higher one of the two operational amplifiers.
When the peak detection value becomes considerably larger than the peak setting value, the output of the operational amplifier 44a is negative and its absolute value increases. Even if the peak detection value increases, the change in detection gain is small, and the absolute value of the output of the operational amplifier 44b is small. Therefore, the output level of the operational amplifier 44b becomes higher than the output level of the operational amplifier 44a, and the difference between the optical gain detection value and the optical gain setting value is input to the pumping light source 29 as a feedback signal so that the optical gain becomes constant. Control is performed.

On the other hand, when the difference between the peak detection value and the peak setting is small, the output level of the operational amplifier 44a becomes higher than the output level of the operational amplifier 44b, and the difference between the peak detection value and the peak setting value becomes a feedback signal to the excitation light source 29. Control is performed so that the peak detection value becomes the peak set value.
In the fourth embodiment, the case where the configuration of FIG. 1 is used as the wavelength multiplexed light peak detection unit 23 has been described. However, the configuration in which the wavelength variable optical filters 13 ₁ to 13 n of FIG. A configuration in which the rectifying filter 16 is provided in the subsequent stage of the wavelength tunable optical filter 13 can be used.

(E) Fifth Embodiment FIG. 14 is a block diagram of a fifth embodiment of the wavelength division multiplexing optical control apparatus of the present invention. Optical gain constant control is performed before the wavelength division multiplexing optical control apparatus of the first embodiment (FIG. 7). This is an example in which an optical fiber amplifier is provided, and constant gain control and maximum value constant control are performed independently. In FIG. 14, 20 is a maximum value constant control unit, and 50 is a light gain constant control unit. The maximum value constant control unit 20 sets the maximum peak value to a constant value, and has the same configuration as the wavelength division multiplexing optical control apparatus of the first embodiment (FIG. 7). 21 is an optical fiber that propagates wavelength-multiplexed light, 22 is an optical branching coupler that branches the wavelength-multiplexed light, 23 is a wavelength-multiplexed light peak detector that detects the peak of the wavelength-multiplexed light, and 24 controls the optical level of the output light. It is a variable optical attenuator. In the wavelength multiplexed light peak detector 23, 13 is a wavelength tunable optical filter, 14 is a photodiode (PD) as photoelectric conversion means, and 15 is a peak detection circuit.

  The optical gain constant control unit 50 makes the ratio (gain) of the output level and input level of the optical fiber amplifier constant, 51 is an optical fiber, 52 and 53 are optical isolators, 54 is a combination of pumping light and signal light. A wavelength multiplexing coupler 55, an optical amplification fiber such as an erbium-doped fiber (EDF) that amplifies signal light, and 56 generates excitation wavelength light having a shorter wavelength and larger energy than the signal light, and inputs it to the optical amplification fiber. A laser diode (pumping light source), 57 is a branch coupler that branches the output light (wavelength multiplexed light) of the optical fiber amplifier, 58 is a photodiode that photoelectrically converts the output light branched by the branch coupler into an electrical signal, and 59 is input light (wavelength). An optical branching coupler 60 for branching multiple light), a photodiode for photoelectrically converting the input light branched by the branching coupler into an electric signal, and 61 for a constant gain control unit. The power of the output light and the power of the input light are obtained based on the electrical signals output from the photodiodes 58 and 60, the optical gain is detected from the ratio thereof, and the feedback signal corresponding to the difference between the detected gain and the set gain is used as the excitation light source. 56 is input.

According to the fifth embodiment, by performing constant gain control in the constant gain control unit 50, the gain of each channel can be made uniform. For this reason, the level of each wavelength can be made substantially uniform, and the maximum value constant control unit 20 can perform constant control of the maximum value by controlling only one wave with the maximum power regardless of the number of channels. The level (power) of each channel can be made uniform.
Further, according to the fifth embodiment, gain tilt maintaining control and light level control per channel are made independent, and there is an effect of avoiding complex control and complication.
In the fifth embodiment described above, the case where the configuration of FIG. 1 is used as the wavelength multiplexed light peak detector 23 is shown. However, the configuration in which the wavelength variable optical filters 13 ₁ to 13 n of FIG. A configuration in which the optical equalizing filter 16 is provided in the subsequent stage of the wavelength tunable optical filter 13 can be used.

(F) Sixth Embodiment FIG. 15 is a block diagram of a sixth embodiment of the wavelength division multiplexing optical control apparatus according to the present invention. Components identical with those of the fifth embodiment of FIG. In the sixth embodiment, the second constant optical gain control unit 70 is provided in the maximum value constant control system 20 of the fifth embodiment, and the optical fiber amplifiers of the constant optical gain control units 50 and 70 are connected in cascade. By doing so, high output can be obtained.

  In FIG. 15, reference numeral 70 denotes a second constant optical gain controller, which has the same configuration as the first constant optical gain controller 50. 71 is an optical fiber, 72 and 73 are optical isolators, 74 is a wavelength multiplexing coupler that combines pumping light and signal light, 75 is an optical amplification fiber such as an erbium-doped fiber (EDF) that amplifies signal light, and 76 is a signal. A laser diode (pumping light source) that generates pumping wavelength light having a wavelength shorter than that of light and has a large energy and inputs it to the optical amplification fiber, 77 is a branching coupler that branches the output light (wavelength multiplexed light) of the optical fiber amplifier, 78 A photodiode for photoelectrically converting the output light branched by the branch coupler into an electrical signal, 79 is an optical branch coupler for branching the input light (wavelength multiplexed light), 80 is a photodiode for photoelectrically converting the input light branched by the branch coupler into an electrical signal, A constant gain control unit 81 obtains the output light power and the input light power based on the electrical signals output from the photodiodes 78 and 80. Detecting the optical gain from their ratio, and inputs the feedback signal corresponding to the difference between the detected gain and set the gain to the excitation light source 76.

According to the sixth embodiment, the constant gain control in the constant gain control units 50 and 70 makes the gain of each channel uniform and makes the level of each wavelength substantially uniform. In addition, since the maximum value constant control unit 20 performs constant maximum value control with the level of each wavelength being substantially uniform, it is possible to perform constant power control of output light by controlling only one wave of maximum power regardless of the number of channels. In addition, the level (power) of each channel can be made uniform. Further, according to the sixth embodiment, it is possible to increase the output and increase the number of channels. Further, by installing the variable optical attenuator 24 between the optical fiber amplifiers, the S / N by the installation of the variable optical attenuator is possible. Degradation can be mitigated and further reduction in excitation efficiency can be suppressed.
In the above sixth embodiment, the case where the configuration of FIG. 1 is used as the wavelength multiplexed light peak detector 23 is shown, but the configuration in which the wavelength variable optical filters 13 ₁ to 13 n of FIG. A configuration in which the optical equalizing filter 16 is provided in the subsequent stage of the wavelength tunable optical filter 13 can be used.

(G) Seventh Embodiment FIG. 16 is a block diagram of a seventh embodiment of the wavelength division multiplexing optical control apparatus according to the present invention. Components identical with those of the sixth embodiment of FIG. The seventh embodiment of FIG. 16 differs from the sixth embodiment in that (1) a constant maximum power control system and a constant total power control system are provided as means for controlling the output light level, and (2) a maximum peak value. The maximum value constant control and the total power constant control are performed based on the value of Ppeak.
In FIG. 15, 91 is an optical power detection circuit for detecting the total power P ₀ of the output light (wavelength multiplexed light) from the electrical signal output from the photodiode 78, and 92 is a multiplex by counting the peak of the electrical signal output from the photodiode 14. A wavelength number counter for detecting the number of wavelength lights (number of multiplexed channels) Nch, 93 is an optical output level control unit, and based on the detected maximum peak value (peak detection value Ppeak) and power detection value P ₀ (1 The feedback signal is input to the pumping light source 29 of the optical fiber amplifier so that the peak detection value becomes the set value or (2) the power detection value becomes the set value.

The optical output level controller 93 is
P ₀ > Ppeak · Nch (1)
If so, the difference between Ppeak · Nch and the set power Ps (= Ps−Ppeak · Nch) is input to the variable optical attenuator 24, and the variable optical attenuator 24 controls the optical level so that the difference becomes zero. . The control for setting the difference between Ppeak · Nch and the set power Ps to zero is, in other words, controlling the detected peak value Ppeak to be the set value (= Ps / Nch). The optical output level control unit 93 is
P ₀ ≦ Ppeak · Nch (2)
If so, the difference (= Ps−P ₀ ) between P ₀ and the set power Ps is input to the variable optical attenuator 24, and the variable optical attenuator 24 controls the optical level so that the difference becomes zero.

When the expression (1) is satisfied, the number of channels is relatively small, and the ASE level (noise level of the optical fiber amplifier) is included. In such a case, even if the power detection value P ₀ is controlled to be constant, since the noise power contained in the light is large, the true optical power cannot be controlled to be constant. Therefore, control is performed so that the detected peak value Ppeak becomes a set value (= Ps / Nch). On the other hand, when equation (2) holds, there is a possibility that the level of one channel is higher than the other due to gain tilt (the gain of each wavelength is different) or the like. In such a case, even if the peak detection value Ppeak is controlled to be the set value (= Ps / Nch), the total optical power cannot be controlled to be constant, and the level difference between the channels cannot be reduced. Therefore, control is performed so that the power detection value P ₀ becomes constant.

In the above seventh embodiment, the case where the configuration of FIG. 1 is used as the wavelength multiplexed light peak detector 23 is shown. However, the configuration in which the wavelength variable optical filters 13 ₁ to 13 n of FIG. A configuration in which the optical equalizing filter 16 is provided in the subsequent stage of the wavelength tunable optical filter 13 can be used.
The present invention has been described with reference to the embodiments. However, the present invention can be variously modified in accordance with the gist of the present invention described in the claims, and the present invention does not exclude these.

  As described above, according to the wavelength division multiplexing photodetection device of the present invention, a single wavelength division multiplexed light can be obtained with a small size and a simple configuration without using a photodiode array, a wavelength multiplexer / demultiplexer, and the like, and without being limited by the number of channels. The maximum power per wave (per channel) can be detected. Further, by providing the periodic sweep means, each wavelength light can be periodically output from the wavelength tunable optical filter, and the peak value / maximum peak value and the number of wavelength multiplexing (number of channels) of each wavelength light can be easily detected. Further, two or more wavelength tunable optical filters are connected in cascade, and each wavelength tunable optical filter is periodically swept synchronously, so that it is possible to output wavelength light with a narrow half-value width, which is advantageous when the wavelength interval is short. Also, by providing an optical equalization filter after the wavelength tunable optical filter, the peak value detection accuracy of each wavelength can be improved, and the detection accuracy of the peak value and the number of multiplexed wavelengths can be improved.

  In addition, according to the wavelength division multiplexing optical control apparatus of the present invention, a single wavelength division multiplexed light can be obtained without using a photodiode array, a wavelength multiplexer / demultiplexer, etc., with a small size and a simple configuration, and without being limited by the number of channels. It is possible to detect the maximum power value per wave and control the maximum value to be equal to the set value. That is, according to the present invention, it is possible to perform constant power control of output light by controlling only one wave with the maximum power. Further, according to the present invention, when two or more wavelength tunable optical filters are connected in cascade and each wavelength tunable optical filter is periodically swept synchronously, wavelength light with a narrow half-value width can be output and the wavelength interval is short. In addition, the detection accuracy of the light level of each wavelength can be improved and the light output level can be controlled with high accuracy. In addition, according to the present invention, by providing an optical equalization filter in the subsequent stage of the wavelength tunable optical filter, it is possible to improve the detection accuracy of the optical power of each wavelength and to perform constant control of the optical output level with high accuracy.

  Further, according to the wavelength division multiplexing light control apparatus of the present invention, based on whether or not the detected maximum peak value protrudes from the level of each wavelength light, (1) feedback so that the peak value becomes a set value. Generate a signal (constant maximum value control), or (2) generate a feedback signal (constant power control) so that the detection power of the output light (wavelength multiplexed light) becomes the set power, and use the feedback signal as an optical fiber Since it is input to the excitation light source of the amplifier, even when the maximum peak value protrudes from the level of each wavelength light, the power can be made constant by the constant power control, and the level difference of each wavelength light can be reduced. It is possible to make the maximum value constant control performed in (1) more effective. In addition, by detecting the number of wavelength multiplexing based on the number of peaks of the electrical signal output from the photoelectric conversion means and changing the set power in accordance with the number of wavelength multiplexing, it is possible to achieve a good light level constant control.

  Further, according to the wavelength division multiplexing light control apparatus of the present invention, based on whether or not the detected maximum peak value protrudes from the level of each wavelength light, (1) feedback so that the peak value becomes a set value. Generate a signal (constant maximum value control), or (2) Generate a feedback signal so that the detection gain becomes the set gain (constant gain control), and input the feedback signal to the pumping light source of the optical fiber amplifier The constant maximum value control can be effectively performed without causing an excessive gain tilt. In other words, if the maximum peak value is prominent, the constant gain control can be performed to make the gain of each channel uniform and the difference in the light level of each wavelength can be reduced, and the maximum constant control performed thereafter can be made more effective. it can. Also, according to the wavelength division multiplexing optical control apparatus of the present invention, the constant gain control is performed in the constant gain control unit to make the gain of each channel uniform, thereby making the maximum value constant in a state where the wavelength light levels are substantially uniform. Since the control is performed, the output light power can be controlled constant by controlling only one wave with the maximum power regardless of the number of channels, and the level of each channel can be made uniform.

  In addition, according to the present invention, even in a wavelength division multiplexing optical control device that enables higher output and other channels by cascading optical fiber amplifiers, the gain of each channel is made uniform by performing constant gain control. As a result, the maximum value constant control is performed with the light levels of the respective wavelengths being substantially uniform, so that the output light power can be controlled constant by controlling only one wave with the maximum power regardless of the number of channels. The level of each channel can be made uniform, and further, high output and multi-channel can be achieved. Further, by installing the variable optical attenuator between the optical fiber amplifiers, the deterioration of S / N due to the installation of the variable optical attenuator can be mitigated, and further, the reduction of the pumping efficiency can be suppressed.

It is 1st Example of the wavelength multiplexing optical detection apparatus of this invention. It is a block diagram of a wavelength variable optical filter. It is a tuning characteristic figure of a wavelength variable optical filter. It is an incident spectrum of wavelength division multiplexed light and light reception level time change explanatory drawing. It is 2nd Example of the wavelength multiplexing optical detection apparatus of this invention. It is 3rd Example of the wavelength multiplexing optical detection apparatus of this invention. It is 1st Example of the wavelength division multiplexing optical control apparatus of this invention. It is 2nd Example of the wavelength division multiplexing optical control apparatus of this invention. It is 3rd Example of the wavelength division multiplexing optical control apparatus of this invention. It is a block diagram of a control correction | amendment part. This is a modification of the third embodiment. It is 4th Example of the wavelength division multiplexing light control apparatus of this invention. It is a block diagram of a control correction | amendment part. It is 5th Example of the wavelength division multiplexing optical control apparatus of this invention. It is a 6th Example of the wavelength division multiplexing optical control apparatus of this invention. It is a 7th Example of the wavelength division multiplexing optical control apparatus of this invention. It is explanatory drawing of the conventional wavelength multiplexing optical detection apparatus. It is a block diagram of the conventional wavelength division multiplexing light detection and control apparatus. It is another block diagram of the conventional wavelength division multiplexing light detection and control apparatus.

Explanation of symbols

13 Wavelength variable optical filter 14 Photodiode (PD) as photoelectric conversion means
DESCRIPTION OF SYMBOLS 15 Peak detection circuit 21 Optical fiber 22 which propagates wavelength multiplexing light Optical branching coupler 23 which branches wavelength multiplexing light Wavelength multiplexing light peak detection part 24 Variable optical attenuator

Claims (7)

An optical fiber amplifier for amplifying the wavelength multiplexed light to propagate;
An optical branching means for branching a part of the wavelength multiplexed light output from the optical fiber amplifier;
A wavelength tunable optical filter that selectively outputs each wavelength of the wavelength-division multiplexed light;
Photoelectric conversion means for photoelectrically converting light output from the wavelength tunable optical filter;
Peak detection means for detecting the maximum peak value of the electrical signal output from the photoelectric conversion means,
Power detection means for detecting the total power of the wavelength multiplexed light output from the optical fiber amplifier;
If the maximum peak value protrudes, power constant control is performed so that the total power becomes the set power, and a feedback signal is generated. If the maximum peak value does not protrude, feedback control is performed by controlling the maximum peak value. Feedback means for generating a signal and inputting the feedback signal to a pumping light source of the optical fiber amplifier;
A wavelength division multiplexing light control apparatus comprising: Comprising means for detecting the number of multiplexed wavelengths based on the number of peaks of the electrical signal output from the photoelectric conversion means;
2. The wavelength division multiplexing optical control apparatus according to claim 1, wherein the set power is changed according to the number of wavelength multiplexing. An optical fiber amplifier for amplifying the wavelength multiplexed light to propagate;
An optical branching means for branching a part of the wavelength multiplexed light output from the optical fiber amplifier;
A wavelength tunable optical filter that selectively outputs each wavelength of the wavelength-division multiplexed light;
Photoelectric conversion means for photoelectrically converting light output from the wavelength tunable optical filter;
Peak detection means for detecting the maximum peak value of the electrical signal output from the photoelectric conversion means,
Means for detecting an optical gain which is a power ratio of input light to the optical fiber amplifier and output light from the optical fiber amplifier;
If the maximum peak value protrudes, the gain is controlled to generate a feedback signal, and if the maximum peak value does not protrude, the maximum peak value is controlled to generate a feedback signal. Feedback means for inputting to the excitation light source of the optical fiber amplifier,
A wavelength division multiplexing light control apparatus comprising: A first optical fiber amplifier for amplifying wavelength-multiplexed light having Nch multichannels to propagate;
First feedback means for inputting a feedback signal to a pumping light source of the first optical fiber amplifier so that an optical gain, which is a power ratio between input light and output light to the first optical fiber amplifier, becomes a set gain;
Optical level control means for controlling the optical level of wavelength multiplexed light output from the first optical fiber amplifier;
A second optical fiber amplifier for amplifying the wavelength multiplexed light output from the optical level control means;
Second feedback means for inputting a feedback signal to the pumping light source of the second optical fiber amplifier so that the optical gain, which is the power ratio between the input light and the output light to the second optical fiber amplifier, becomes the set gain;
Optical branching means for branching a part of the wavelength multiplexed light output from the second optical fiber amplifier;
A wavelength tunable optical filter that selectively outputs each wavelength of the wavelength-division multiplexed light;
Photoelectric conversion means for photoelectrically converting light output from the wavelength tunable optical filter;
Peak detection means for detecting the maximum peak value Ppeak of the electrical signal output from the photoelectric conversion means;
Power detection means for detecting the total power P ₀ of the wavelength multiplexed light output from the second optical fiber amplifier;
P ₀ > Ppeak · Nch
If so, the difference between Ppeak · Nch and the set power Ps (= Ps−Ppeak · Nch) is input to the light level control means,
P ₀ ≦ Ppeak · Nch
If so, a third feedback means for inputting the difference between P ₀ and the set power Ps (= Ps−P ₀ ) to the light level control means,
A wavelength-division-multiplexed light control apparatus, wherein the light level control means performs light level control based on the input signal . Comprising means for detecting the number of multiplexed wavelengths based on the number of peaks of the electrical signal output from the photoelectric conversion means;
5. The wavelength division multiplexing optical control apparatus according to claim 4, wherein the set power is changed according to the number of wavelength multiplexing. One or more other wavelength tunable optical filters are cascade-connected to the wavelength tunable optical filter, and each wavelength tunable optical filter is periodically synchronously swept,
5. The wavelength division multiplexing light control apparatus according to claim 1, 3 or 4. Optical equalization filter in the latter stage of the tunable optical filter,
5. The wavelength division multiplexing light control apparatus according to claim 1, wherein the wavelength division multiplexing light control apparatus is provided.

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