JPH04250729A - Wavelength filter automatic tuning controller - Google Patents

Abstract

PURPOSE:To control an identification signal fed to a filter incident optical signal independently of its phase state by reducing number of identification signals to be fed to a light source into one signal for each light source so as to attain the automatic rising of the control system. CONSTITUTION:In order to implement tracing control of a transmission center wavelength of a wavelength filter 120 being the controlled system to a wavelength filter input optical wavelength, the transmission center wavelength of the wavelength filter is modulated minutely by an oscillator 161 to discriminate a phase change in a modulation component of a wavelength filter output light in this case. Moreover, the transmission center wavelength of the wavelength filter 120 being the controlled system is swept at the rising of the controller and the sweeping is stopped when one wave of the wavelength multiplex light being the input light to the wavelength filter (not necessary to be coincident with the transmission center wavelength set at the rising) is transmitted through the wavelength filter and the usual automatic tuning control tracing control is transited. Furthermore, the phase of an output pulse of a frequency synthesizer 180 is minutely modulated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic tuning control device for a wavelength filter that selects light of a predetermined wavelength from an input optical signal.

0002

2. Description of the Related Art In recent years, there has been an increasing demand for communication services using wideband signals such as image signals. Since the bandwidth of wideband signals ranges from several MHz to several tens of MHz, we use an electrical-to-optical converter as a transmitter, which converts electrical signals into optical signals, as a transmission line with a smaller diameter, wider bandwidth, and lower loss than conventional coaxial cables. 2. Description of the Related Art Optical fiber transmission systems that use optical fibers, which have advantages such as resistance to electromagnetic induction, and optical-to-electrical converters that convert optical signals into electrical signals as receivers, are becoming widely adopted.

Furthermore, since a single optical fiber can transmit optical signals of multiple wavelengths, optical signals of different wavelengths from multiple electrical-to-optical converters are combined, transmitted through a single optical fiber, and received. On the other hand, studies are also being conducted on a wavelength multiplexing optical transmission system in which optical signals are separated for each wavelength and received by a plurality of optical-to-electrical converters.

[0004] In wavelength division multiplexing transmission systems, there are cases in which an optical signal of a predetermined wavelength is selected from a wavelength multiplexed signal in the middle of a wavelength multiplexed transmission line connecting a transmitter and a receiver, and the selected optical signal is switched to another transmission line. be. At this time, as a means for selecting an optical signal of a predetermined wavelength from a wavelength multiplexed signal, there is a wavelength filter using a (distributed feedback semiconductor laser) DFBLD described in Lecture No. 326 of the Proceedings of the 1985 Institute of Electronics and Communication Engineers Divisional Conference. This DFBLD operates as a current-controlled wavelength filter whose center wavelength can be varied by changing the value of the injected current below the oscillation threshold. However, the wavelength filter using this DFBLD is
Since it is made of P-based material, the center wavelength has a temperature characteristic of about 1 A/°C. Therefore, it is necessary to control the wavelength filter so that it is always tuned to an optical signal of the correct wavelength even if the temperature fluctuates. Furthermore, in a wavelength division optical switch that sets a communication channel between arbitrary wavelengths of wavelength-multiplexed input and output optical signals, the operation of selecting an optical signal of a predetermined wavelength from the wavelength-multiplexed signal using a wavelength filter is performed within the optical switch. Even in this case, it is necessary to control the wavelength filter so that it is tuned to an optical signal of a predetermined wavelength.

Conventionally, a wavelength filter automatic tuning control method described in Japanese Patent Application Laid-Open No. 1-177518 has been known as such a wavelength filter automatic tuning control method. FIG. 6 is a block diagram of this conventional example. Optical wavelength multiplexing circuit 11 in FIG.
The configuration of 00 is shown in FIG. Here, as an example, we will use 3 light sources.
It is made into individual pieces. In the optical wavelength multiplexing circuit 1100, each light source 12
10, 1220, 1230 (wavelengths λ1, λ2,
λ3) Identification signal 10 with sufficiently low frequency compared to the data signal
01, 1002, 1003 (frequency f1, f2 respectively
, f3 sine waves). The emitted light from each light source is further converted into data signals 1270, 1280, 1290 and second identification signals 1001', 1002', 1003' (frequency f1 /2, f2 /2, respectively) using external modulators 91, 92, 93. , f3/2 sine wave). The modulator output light is multiplexed by a wavelength multiplexer 1200 and output to a wavelength multiplex transmission line 1110. Note that the identification signals 1001, 1001', 10
The phases of 02 and 1002' and 1003 and 1003' are set to be the same. In FIG. 6, wavelength multiplexed light sent through a wavelength multiplex transmission line 1110 passes through a wavelength filter 1120 and is then photoelectrically converted by a photodiode 1132. The output of the photodiode 1132 is used to extract the identification signal.
Bandpass filter 1140 (identification signals 1001', 10
02', 1003'), 1150 (identification signal 10
01, 1002, 1003 are extracted). The output of the bandpass filter 1140 is sent to the next phase phase-locked loop (
PLL) 1142 (see FIG. 8 for the configuration), the signal is converted into a sine wave whose phase remains unchanged and whose frequency is doubled (ie, f1, f2, f3). The output of the PLL 1142 and the output of the bandpass filter 1150 are multiplied by a multiplier 1160. Assuming that the transmission characteristic of the wavelength filter 1120 is unimodal with respect to the input wavelength, the identification signals 1001, 1002, 1003 applied to the input light as an FM modulation signal are determined according to the magnitude relationship between the transmission center wavelength and the input light wavelength. The phase of remains unchanged or reverses. Furthermore, when the filter transmission center wavelength and the input light wavelength match, identification signals 1001, 1002, 1
003 is converted into a sine wave with double frequency. On the other hand, the identification signals 1001', 1002', and 1003' applied to the input light as intensity modulation signals remain unchanged between input and output of the filter, regardless of the wavelength of the filter and the input light. Therefore, if the output voltage when the multiplier 1160 output is applied to the low-pass filter 1161 is plotted against the difference between the filter transmission center wavelength and the input light wavelength, it will be zero at the point where the difference is zero, and before and after that, the output voltage will be zero. Since the discrimination characteristic of changing the sign can be obtained, it is possible to control the transmission center wavelength of the wavelength filter 1120 to follow the input light wavelength by using the output of the low-pass filter 1161 as an error signal.

[0006] Also, identification signals 1001, 1002, 10
03 indicates that the input light passing through the wavelength filter 1120 is 3
It is also used by the control device to recognize which of the two. The identification signals 1001, 1002, 1003 output from the bandpass filter 1150 are converted by the waveform converter 195 into a pulse train whose repetition frequency is the same as the input frequency, and then input to the frequency comparator 181 together with the output of the frequency synthesizer 1180. be done. The frequency synthesizer selects f1, f2, f3 according to external input.
A pulse train having one of the repetition frequencies is output. The frequency comparator 1181 is configured as shown in FIG. 9, and compares the repetition frequencies of the two pulse train inputs applied to the input terminals 1101 and 1102, increases or decreases the output voltage depending on the magnitude, and makes sure that both inputs are repeated at the same time. If it has a frequency, it has the function of holding the previous output voltage. Therefore, the frequency synthesizer 1 applied to the input terminal 1102
By setting the repetition frequency of the output pulse train of 180,
The wavelength of the input light that passes through the wavelength filter 1120 can be changed arbitrarily.

In the frequency comparator 1181, the SR flip-flop 1500 and the D flip-flop 1510 first determine whether or not a pulse train has arrived at the input terminal 1101. When the pulse train is arriving, D flip-flop 1
The output of 510 is held high and the AND gate 1
520 and 1521 are both turned on. N-ary counter 15
40 and 1541 count the number of pulses of the pulse train input to the input terminals 1101 and 1102, and when the number of pulses of either one reaches N, all counters are reset. At this stage, it is determined that the repetition frequency of the input corresponding to the N-ary counter that reached N first is higher. On the other hand, when the repetition frequencies of both inputs are equal, the counting result of the M-ary counter (N≦M<2N) 1550 that receives the logical sum of both input pulse trains is
The count results of the advance counters 1540 and 1541 reach M before they reach N, and all counters are reset. The outputs of the N-ary counters 1540 and 1541 are S
The S value is input to the set inputs of R flip-flops 1501 and 1502, and corresponds to the N-ary counter that reached N first.
Hold the R flip-flop high. two S's
The outputs of R flip-flops 501 and 502 are input to control signal generation circuits 1560 and 1561, respectively. The control signal generation circuits 1560 and 1561 monotonically increase or decrease the output voltage while the input is held at a high level (the direction of increase and decrease is reversed in 1560 and 1561). Further, while the input is held at low level, the value of the output immediately before the input shifts to low level is held. On the other hand, the output of the M-ary counter 550 is input to the reset inputs of the SR flip-flops 1501 and 1502. Therefore, the output of the frequency comparator 1181 is the input terminal 1101,
When the repetition frequencies of the pulse trains input to the pulse train 1102 differ, the output electrons increase or decrease depending on the magnitude relationship. Furthermore, when the repetition frequencies are the same, the output voltage does not change. Furthermore, when the frequency comparator 1181 increases or decreases the output voltage in order to switch the transmission center wavelength of the wavelength filter 1120, the wavelength filter 1120 does not transmit any of the input light until it reaches the target value. Therefore, there is a state in which no pulse train appears at the input terminal 1101 of the frequency comparator 1181. At this time, AND gates 1520 and 1521 are both turned off, and N-ary and M-ary
Since the forward counter does not count, all its outputs are fixed at low level. At this time, since the set and reset inputs of the SR flip-flops 1501 and 1502 are both held at low level, the state immediately before the pulse train at the input terminal 1101 disappears is held. Therefore, even in a transient situation where there is no light transmitted through the wavelength filter, automatic tuning is performed without momentary interruption.

[0008]

[Problems to be Solved by the Invention] In the conventional wavelength filter automatic tuning control system described above, as shown in FIG.
Each light source must be modulated with a street identification signal, one with FM modulation and the other with intensity modulation. Also, considering that a semiconductor laser is used as a light source,
Direct intensity modulation parasitically accompanies FM modulation and causes malfunctions in control, so it is necessary to perform intensity modulation using an external modulator, which inevitably complicates the system and increases cost. Furthermore, like an acousto-optic wavelength filter, the transmission width is 10 to 20
When controlling a wavelength filter with a wavelength of several angstroms, it is necessary to apply FM modulation to the light source with a depth of several angstroms. It is extremely difficult to realize depth FM modulation by direct modulation.

Furthermore, in the above configuration, it is necessary to set the wavelength filter transmission wavelength in advance so that one of the wavelength-multiplexed input lights is output from the wavelength filter and the identification signal arrives at the frequency comparator.

Furthermore, in the above configuration, when the phases of the identification signal arriving at the frequency comparator and the frequency synthesizer output signal match, even if the two are logically summed, only a pulse train with the same repetition frequency is formed, which is not as expected. A pulse train consisting of the sum of the numbers of both pulses is not formed. In this case, although the M-ary counter should have completed M counts first, the N-ary counter completes N counts first, leading to malfunction.

An object of the present invention is to eliminate such drawbacks of the prior art, and to provide a system that requires only one identification signal to be applied to each light source.
Furthermore, it is an object of the present invention to provide a wavelength filter automatic tuning control device that does not require an external modulator, can be started up automatically, and can be expected to operate stably regardless of the phase of the pulse train input to the frequency comparator.

0012

[Means for Solving the Problems] In order to achieve the above-mentioned object, in the present invention, output light from a wavelength filter inputs signal light whose intensity is modulated by mutually different identification signals predetermined for each wavelength. a photodetector for converting into an electrical signal; a first signal source for generating a signal different from the identification signal; a multiplier for multiplying the output of the first signal source by the output of the photodetector; an integrator that integrates the output of the multiplier; a filter that allows only the identification signal to pass among the outputs of the photodetector; and a second signal source that outputs one of the identification signals based on external input. a frequency comparator that compares the output of the second signal source and the output of the filter and increases or decreases the output voltage based on the magnitude of the frequency of both; It is characterized by comprising an adder that adds the output and the output of the integrator, and a wavelength filter driver that converts the output of the adder into a signal that drives the wavelength filter.

[0013] A photodetector that converts the output light from a wavelength filter into an electrical signal, which receives signal light modulated by different identification signals predetermined for each wavelength into an electric signal; A filter that passes only the identification signal, and one of the identification signals based on external input.
a frequency comparator that compares the output of the signal source with the output of the filter and increases or decreases the output voltage based on the magnitude of the frequency of both; and a frequency comparator that drives the wavelength filter with the output of the frequency comparator. In a wavelength filter automatic tuning control device comprising a wavelength filter driver that converts a signal into a signal, the transmission wavelength of the wavelength filter is swept at startup, and the sweeping is stopped when one of the identification signals is output from the filter. Characterized by having the means.

[0014] A photodetector that converts the output light from a wavelength filter into an electric signal, which receives signal light modulated by different identification signals predetermined for each wavelength, and the above-mentioned among the outputs of the photodetector. A filter that passes only the identification signal, and one of the identification signals based on external input.
a frequency comparator that compares the output of the signal source with the output of the filter and increases or decreases the output voltage based on the magnitude of the frequency of both; and a frequency comparator that drives the wavelength filter with the output of the frequency comparator. A wavelength filter automatic tuning control device comprising a wavelength filter driver for converting a signal into a signal that is characterized in that the output from the signal source is subjected to phase modulation.

[0015]

[Operation] As described above, in the present invention, in order to control the transmission center wavelength of the wavelength filter to be controlled to follow the wavelength filter input light wavelength, the transmission center wavelength of the wavelength filter is slightly modulated. It discriminates the phase change of the modulation component of the wavelength filter output light. Therefore, in the optical wavelength multiplexing circuit, there is no need to apply this identification signal for follow-up control to the light source, and it is sufficient to apply one light source wavelength identification signal for automatic tuning control, reducing the number of necessary identification signals. .

Furthermore, in the present invention, when the control device is started up, the transmission center wavelength of the wavelength filter to be controlled is swept, and one wave (set at the time of startup) of the wavelength multiplexed light that is the input light to the wavelength filter is swept. When the wavelength filter passes through the wavelength filter, the sweep is stopped and normal automatic tuning control and follow-up control are performed. By such an operation, the transmission center wavelength set at startup is automatically pulled in after startup.

Further, in the present invention, the phase of the output pulse of the frequency synthesizer is slightly modulated. Therefore, even if the phases of both input pulses input to the frequency comparator match at a certain point, since the phase of one pulse gradually changes, the logical sum of the next synchronized pulse will be from the two pulses. You can make it look like it is. Therefore, there is almost no influence from the fact that the pulse phases match.

[0018]

EXAMPLES The present invention will now be explained in detail with reference to examples. FIG. 1 is a diagram showing an embodiment of the present invention.

In the optical wavelength multiplexing circuit 100, the emitted lights of three semiconductor lasers having mutually different wavelengths are combined and sent to a wavelength multiplexing transmission line 110. FIG. 2 shows a configuration diagram of the optical wavelength multiplexing circuit 100. Semiconductor laser 310, 32
The oscillation wavelengths of 0,330 are 1.55 μm and 1.5 μm, respectively.
They are arranged at 2 nm intervals of 52 μm and 1.554 μm. Sine waves having frequencies of 1 kHz, 2 kHz, and 4 kHz are applied to semiconductor lasers 310, 320, and 330, respectively, as identification signals. On the other hand, data signals 270, 280, and 290 are also applied to each semiconductor laser. The data signal and the identification signal are sent to adders 360, 370, 38.
After being added with 0, it is input as a change in the injection current of the semiconductor laser, and is used to directly modulate the intensity of the semiconductor laser output light. The output lights from the semiconductor lasers 310, 320, and 330 are multiplexed by a three-input star coupler 340, and then sent onto a wavelength multiplex transmission line 350. The wavelength multiplexing transmission line 350 is connected to the input of an acousto-optic wavelength filter (AO filter) 120, and a desired wavelength is selected by the AO filter 120. The output light of the AO filter 120 is split into two by a splitter 130, one of which is sent to the photodetector 13.
2 for optical/electrical conversion. Regarding the operating principle and characteristics of the acousto-optic wavelength filter, please refer to S. E. Journal of the Optical Society of America by Harris et al.
he Optical Society of A
merica) Vol. 59 No. 6 (published in 1969) 744
For details, see the paper on pages 747 to 747. The transmission center wavelength of the AO filter 120 is modulated by a 50 kHz sine wave that is the output of the constant oscillator 161. Furthermore, since the transmission center wavelength of the AO filter 120 changes depending on the frequency of a sine wave of approximately several hundred MHz input from the outside, the output signal frequency changes monotonically with respect to the external input voltage to drive the AO filter. A functional AO filter driver 190 is used.

A portion of the output electrical signal of the photodetector 132 is
Multiplied by a part of the output of the oscillator 161, the integrator 20
0, only that DC component is selected and fed back to the AO filter 120 via the amplifier 210. Multiplier 160 to A
The series of paths reaching the O filter 120 is responsible for controlling the transmission center wavelength of the AO filter 120 to follow the input light wavelength, which was mentioned in the prior art section. Note that the oscillator 161 superimposed on the two inputs arriving at the multiplier 160
The path lengths of both are adjusted as appropriate so that the phases of the output sine waves match.

A part of the output of the photodetector 132 has a cutoff frequency of 5, which is arranged to transmit only the identification signal.
After passing through a kHz low-pass filter 220, a rectangular pulse train having the same repetition frequency as the passed identification signal is generated.
The waveform converter 230 (see FIG. 4) converts the signal.

The output pulse train of the waveform converter 230 is input to the input terminal 1 of the frequency comparator 181, and a frequency synthesizer whose output is a rectangular pulse train having a repetition frequency of 1 kHz, 2 kHz, or 4 kHz according to an external selection signal. 180 output is applied to input terminal 2. Since the main operations of the frequency comparator 181 are the same as those described in the prior art, only the portions improved by the present invention will be described here.

First, when starting up the control system according to the present invention, switch 515 shown in FIG. 3 is turned on. An SR flip-flop 503 for chattering prevention shapes the voltage appearing at the switch 515 before and after the switch is turned on into a step function having a single rising edge, and the next monostable multivibrator 591 converts it into a single pulse. This pulse is input to SR flip-flops 501 and 502 via OR gates 532 and 533, respectively, to set and reset states. After the single pulse leaves, the set inputs and reset inputs of the SR flip-flops 501 and 502 are all at low level until the identification signal arrives at the input terminal 1, so the states of the SR flip-flops are maintained. . During this time, since a high level is continuously output from the output of the SR flip-flop 501, the output voltage of the integrator 590 increases linearly, and accordingly, the transmission center wavelength of the AO filter 120 is also swept in one direction. During this time, the output of the NOR gate 534 is held at a low level, so the switch 185 to which the output terminal 512 is connected is opened, and the inverted output (Q) of the SR flip-flop 504 is held at a low level during this time, so the The integrator 200 is turned off, and the tracking control of the AO filter transmission wavelength to the input light wavelength is turned off. When one of the wavelength-multiplexed lights passes through the AO filter 120 during sweeping and an identification signal arrives at the input terminal 1, a comparison is made with a reference signal frequency corresponding to the desired transmitted wavelength and supplied from the frequency synthesizer 180. The sweep of the AO filter transmission center wavelength changes depending on its magnitude. When the two finally match, the output of the M-ary counter 550 rises to a high level, which causes the SR flip-flop 50 to
4 is reset and its inverted output (Q bar) goes high, turning on integrator 200 of FIG. Since the set input of the SR flip-flop 504 is at low level except immediately after the switch 515 is turned on, the SR flip-flop 5
The inverted output (Q bar) of 04 remains at a high level until the switch 515 is turned on again, so the integrator 200 remains on. Further, when the signal frequencies arriving at the input terminals 1 and 2 match, the output of the NOR gate 534 is kept at a high level, so that control of the AO filter transmission wavelength to follow the input light wavelength is turned on.

In this state, when the frequency of the reference signal output from the frequency synthesizer 180 is changed in order to change the transmission wavelength of the AO filter, the SR flip-flop 501 or 502 is set, the NOR gate is turned off, and the switch 185 is turned off. Cut. At this time, since the integrator 200 holds the previous output voltage for a certain period of time, the AO filter transmission wavelength is not swept in the opposite direction to the target.

The subsequent automatic tuning of the filter transmission wavelength and the follow-up control to the input light wavelength are performed in the same manner as described above.

[0026] Subsequently, the frequency comparator 181 receives 2
A method for avoiding a decrease in the number of input pulses to an M-ary counter when the phases of two pulse trains almost match will be described below, which was a problem in the prior art. First, M-ary counter 550
The gate provided at the input is changed to Ex-OR gate 530. By doing so, it becomes possible to output the pulse as two pulses, except when both pulse phases completely match. Next, as a countermeasure in the case of a complete match, AN
The output pulse train of the D gate 521 is subjected to pulse phase modulation. By doing this, the complete coincidence of both pulse phases occurs only once in one cycle of pulse phase modulation, and one cycle length is equal to the pulse repetition frequency (1kHz, 2kHz, 4kHz).
By setting the time period to be sufficiently smaller than the reciprocal of 10 ms, the frequency of pulse disappearance can be significantly reduced. At this time, for a 1 kHz pulse train in which both inputs are completely in phase, the frequency of pulse disappearance can be reduced to 1 in 10. This corresponds to a 10% decrease in one pulse repetition frequency, but if the count values M and N of the counter at the subsequent stage are, for example, M=10 and N=6, the ratio of both input pulse frequencies is 1.5. This amount of decrease is not a problem since it is considered to be the same frequency. The configuration of the pulse phase modulation circuit 580 is shown in FIG. The integrator is turned on and off by inverting the input pulse train, generating a sawtooth wave train. An adder 710 superimposes the output sine wave (100 Hz) of the oscillator 700 on this signal. Next, a comparator 720 performs a comparison with a constant level to obtain a pulse width modulated wave, and a monostable multivibrator 730 converts this into a pulse train of the same pulse width to obtain a pulse phase modulated wave.

In the above embodiments, an AO filter was assumed as the wavelength filter to be controlled, but the invention is not limited to this, and any filter whose transmission center frequency can be changed by external input, such as a DFB LD type filter, may be used.

[0028]

As described above, in the wavelength filter automatic tuning control device of the present invention, only one identification signal is used for each light source, and there is no need to use an external modulator. The device can be simplified.

Furthermore, in the present invention, the transmission center wavelength of the wavelength filter is swept when the control device is started up, and when the sweep is stopped, it is possible to shift to normal operation, thereby achieving automation from the time of start-up. .

Furthermore, the present invention makes it possible to avoid control malfunctions when the phases of the incoming identification signal and the reference signal match. Even if this occurs, normal control operation can be expected.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a wavelength filter automatic tuning control device.

FIG. 2 is a configuration diagram of an optical wavelength multiplexing circuit 100.

FIG. 3 is a configuration diagram of a frequency comparator 181.

FIG. 4 is a configuration diagram of a wavelength converter 230.

FIG. 5 is a configuration diagram of a pulse phase modulation circuit 580.

FIG. 6 is a configuration diagram of a wavelength filter automatic tuning control device using a conventional technique.

FIG. 7 is a configuration diagram of an optical wavelength multiplexing circuit 100 of a wavelength filter automatic tuning control device using a conventional technique.

FIG. 8 is a configuration diagram of a PLL 142 of a wavelength filter automatic tuning control device using a conventional technique.

FIG. 9 is a configuration diagram of a frequency comparator 181 of a wavelength filter automatic tuning control device using a conventional technique.

[Explanation of symbols]

100, 1100 Optical wavelength multiplexing circuit 350, 1110 Wavelength multiplexing transmission line 120 AO filter 130, 1130 Brancher 132, 1132 Photodetector 160, 1160 Multiplier 161, 700, 1310 Oscillator 162, 710 Adder 180, 1180 Frequency synthesizer 181 ,11
81 Frequency comparator 190 AO filter driver 200 Integrator 210, 1162 Amplifier 220, 1161 Low pass filter 230, 195
Waveform converter 1, 2, 1101, 1102 Input terminal 511, 51
2,513 Output terminals 310, 320, 330 Semiconductor lasers 270, 28
0,290 Data signal 21,22,23,1001
,1002,1003,1001',1002',10
03' Identification signal 360, 370, 380, 1240
, 1250, 1260 Adder 340 Star coupler 500, 501, 502, 503, 504, 1500,
1501, 1502SR flip-flop 510, 15
10 D flip-flop 520, 521, 1520
, 1521 AND gate 530 Ex-OR gate 531, 532, 533, 1530, 1531 OR
Gates 540, 541, 1540, 1541 N-ary counter 550, 1550 M-ary counter 534 NOR gate 570 Delay element 580 Pulse phase modulation circuit 590 Integrator 591, 420, 730 Monostable multivibrator 410, 720 Comparator 560, 561 Control signal Generation circuit 1140, 1150 Band pass filter 1142
PLL 1120 Wavelength filter 1170 Filter drive circuit 1300 Phase comparator 1320 1/2 frequency divider 1210, 1220, 1230 Light source 91, 92, 9
3 External modulator 1200 Wavelength multiplexer

Claims (3)

[Claims] 1. A photodetector that converts output light from a wavelength filter into an electrical signal, which inputs signal light intensity-modulated by different identification signals predetermined for each wavelength, and the identification signals are different from each other. a first signal source that generates a signal; a multiplier that multiplies the output of the first signal source by the output of the photodetector; an integrator that integrates the output of the multiplier; a filter that allows only the identification signal to pass among the outputs; a second signal source that outputs one of the identification signals based on external input; and an output of the second signal source and an output of the filter. a frequency comparator that compares and increases or decreases the output voltage based on the magnitude of both frequencies;
It consists of an adder that adds the output of the frequency comparator, the output of the second signal source, and the output of the integrator, and a wavelength filter driver that converts the output of the adder into a signal that drives the wavelength filter. A wavelength filter automatic tuning control device characterized by: 2. A photodetector that converts output light from a wavelength filter into an electrical signal, which inputs signal light modulated by mutually different identification signals predetermined for each wavelength;
A filter that allows only the identification signal to pass among the outputs of the photodetector, a signal source that outputs one of the identification signals based on external input, and a comparison between the output of this signal source and the output of the filter. In a wavelength filter automatic tuning control device consisting of a frequency comparator that increases or decreases the output voltage based on the magnitude of both frequencies, and a wavelength filter driver that converts the output of the frequency comparator into a signal that drives the wavelength filter, 1. A wavelength filter automatic tuning control device, comprising means for sweeping the transmission wavelength of the wavelength filter when the wavelength filter is raised, and stopping the sweeping when one of the identification signals is output from the filter. 3. A photodetector that converts output light from a wavelength filter into an electrical signal, which inputs signal light modulated by mutually different identification signals predetermined for each wavelength;
A filter that allows only the identification signal to pass among the outputs of the photodetector, a signal source that outputs one of the identification signals based on external input, and a comparison between the output of this signal source and the output of the filter. and a wavelength filter automatic tuning control device comprising a frequency comparator that increases or decreases the output voltage based on the magnitude of both frequencies, and a wavelength filter driver that converts the output of the frequency comparator into a signal that drives the wavelength filter. A wavelength filter automatic tuning control device comprising means for applying phase modulation to an output from a signal source.