JP4690658B2 - Laser modulation wave adjustment device - Google Patents

Description

  The present invention relates to a laser modulation wave adjusting device that adjusts a low frequency signal by acquiring amplitude displacement and / or frequency displacement of the low frequency signal on a laser beam when a low frequency signal is superimposed on a laser diode. It is.

  Conventionally, in an optical communication system using a laser diode for communication, a sub-signal that is a low-frequency signal is superimposed on a main signal output from the laser diode to transmit route information, maintenance information, etc., or a dither signal As described above, the spectral line width of the main signal is widened to suppress stimulated Brillouin scattering (SBS).

  Here, as the low-frequency signal to be superimposed on the laser light, a plurality of low-frequency signals are used, and a transmission signal such as path information and a dither signal are superimposed separately, and one low-frequency signal is mainly used as path information. In some cases, the transmission signal is also used as a dither signal.

JP 2000-164977 A

  However, if the laser diode is operated for a long period of time, the deterioration of the laser diode will occur and the characteristics of the laser diode will change. Therefore, even if the bias voltage change that modulates the low-frequency signal is kept constant, There was a problem that sometimes was not constant.

  In addition, providing a circuit that detects whether the frequency change amount on the laser beam is constant, and controlling the frequency displacement amount on the laser beam to be constant using this detection result complicates the configuration and reduces the number of parts. There has been a problem that increases.

  In general, a laser diode has a wavelength lock function for keeping the wavelength of laser light constant. Specifically, the wavelength lock function is obtained by branching the monitor light of the laser light into two, outputting one through a light receiving element such as a photodiode, and passing the other through a filter having a predetermined frequency transmission characteristic. Is used to detect the wavelength variation of the laser beam using the ratio of each output value, and based on this detection result, the temperature is controlled to be constant using temperature control means such as a Peltier element. is there.

The present invention was made in view of the above, to provide a laser modulated wave adjustment device capable of adjusting a laser beam amplitude change in caused by low-frequency signal superimposed on the laser light reliably and easily For the purpose.

In order to solve the above-described problems and achieve the object, the present invention branches light monitored from a laser diode, receives one branched light with a first light receiving element, and compares the other with respect to the other branched light. Performing wavelength lock control of laser light output by the laser diode based on values received by the first and second light receiving elements after filtering the predetermined wavelength components and receiving the light from the first and second light receiving elements, In the laser modulation wave adjustment device that outputs a predetermined low frequency signal superimposed on a laser beam, the predetermined low frequency superimposed on the laser beam based on values received by the first and second light receiving elements. acquisition means for acquiring the amplitude displacement of the laser light generated by the frequency signal, on the basis of the amplitude displacement of which has been acquired by the acquisition unit, the amplitude of the predetermined low frequency signal inputted to the laser diode Is of, is characterized in that and a adjusting means for adjusting the amplitude displacement of the laser light generated by said predetermined low frequency signal constant.

Further, according to the present invention, the light monitored from the laser diode is branched, one branched light is received by the first light receiving element, and the second branched light is filtered by the predetermined wavelength component with respect to the other branched light. Based on the values received by the element and received by the first and second light receiving elements, wavelength lock control of the laser light output from the laser diode is performed, and the first low frequency signal and the second light are output to the laser light. In the laser modulation wave adjustment device that superimposes and outputs the low frequency signal, the first and / or second superimposed on the laser beam based on values received by the first and second light receiving elements. the amplitude of the acquisition means for acquiring the amplitude displacement of the laser light generated by the low-frequency signal, based on the amplitude displacement of which has been acquired by the acquisition means, the predetermined low frequency signal inputted to the laser diode Is changed, characterized in that and a adjusting means for adjusting the amplitude displacement of the laser light generated by said first and / or second low frequency signal constant.

The present invention further includes a sampling unit that performs high-speed sampling of values received by the first and second light receiving elements in the above-described invention, wherein the acquiring unit includes a part of the data sampled by the sampling unit or It said predetermined low frequency signal using the whole, and the first low-frequency signal or features to obtain the amplitude displacement of the laser light generated by said second low-frequency signal.

  According to the present invention, in the above invention, when the first and second switches provided in the subsequent stage of the first and second light receiving elements and the switching between the first and second switches are time-division controlled. Division control means.

  According to the present invention, in the above invention, a deterioration estimating means for estimating deterioration of the laser diode based on an adjustment history of the first low-frequency signal to be adjusted by the adjusting means, and the deterioration estimating means Deterioration adjustment means for adjusting the second low-frequency signal using the estimation result.

According to the present invention, the predetermined low-frequency signal, the first low-frequency signal, or the second low-frequency signal to be superimposed on the laser light can be effectively used with a simple and small number of parts by using the wavelength lock function that has already been arranged. an effect that can adjust the amplitude displacement of the laser light generated by the signal constant.

  Embodiments of a laser modulation wave adjusting apparatus according to the present invention will be described below with reference to the drawings.

(Embodiment 1)
1 is a block diagram showing a configuration of a laser apparatus including a laser modulation wave adjusting apparatus according to Embodiment 1 of the present invention. In FIG. 1, the laser device includes a laser diode (LD) 1 that outputs laser light having a variable wavelength around the center wavelength. The monitor light from the LD 1 detects the wavelength fluctuation by the wavelength locker 2, and controls the wavelength of the laser light by controlling the temperature of the Peltier element 4 by the wavelength control circuit 3.

  The wavelength locker 2 receives the monitor light of the laser beam by the mirror 11 and splits it into two. One light is output to a photodiode (PD) 13 as a light receiving element, and the other light has a predetermined frequency. The light is output to a photodiode (PD) 14 as a light receiving element through an optical filter 12 that transmits light. The signals received by the PDs 13 and 14 are output to the comparator 17 via the low pass filters 15 and 16, respectively. The comparator 17 detects a change in wavelength based on the output ratio from the PDs 13 and 14 and outputs the result to the wavelength control circuit 3.

On the other hand, the comparator 5 detects the amplitude change of the low frequency signal f as dither signal on the basis of the output from PD13,14, and outputs the result to the low-frequency control circuit 6. Comparator 5, by dividing the input from the PD13 and PD14 input signal, detects the amplitude change of the laser light generated by the low frequency signal. Low-frequency control circuit 6, based on the amplitude change signal outputted from the comparator 5 controls the amplitude of the input low-frequency signal f, and outputs the controlled low-frequency signal to LD1. The low-frequency signal f is a transmission signal such as route information, and this transmission signal is also used as a dither signal.

According to the first embodiment, by effectively utilizing the existing wavelength locker 2 detects the amplitude change on laser beam that is currently output, the laser light generated by the low-frequency signal based on this result since so as to adjust the amplitude, it is possible to adjust the laser beam amplitude caused by a high frequency signal accuracy with a simple configuration.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the first embodiment described above, analog processing is performed on the signals acquired by the PDs 13 and 14, but in the second embodiment, digital processing is performed.

  FIG. 2 is a block diagram showing a configuration of a laser apparatus including a laser modulation wave adjusting apparatus according to Embodiment 2 of the present invention. In FIG. 2, this laser apparatus is provided with a digital signal processing unit 20 at the subsequent stage of the PDs 13 and 14. The digital signal processing unit 20 is replaced with the low-pass filters 15 and 16 and the comparators 5 and 17 in the laser apparatus shown in FIG. Other configurations are the same as those of the first embodiment, and the same reference numerals are given to the same components.

The digital signal processing unit 20 performs high-speed sampling on the signals detected by the PDs 13 and 14 by the high-speed sampling unit 21, respectively. High-speed sampling is performed in order to acquire sampling data for controlling a low frequency signal in addition to sampling data necessary for performing wavelength control by the wavelength locker 2. The sample acquisition circuits 22 and 23 respectively acquire a predetermined number of data sampled by the high-speed sampling unit 21 and output the data to the comparators 25 and 27, respectively. The comparator 25 is a digital signal processing circuit for obtaining an amplitude change of the low frequency signal, the result is output to the low-frequency control circuit 6. On the other hand, the comparator 27 is a circuit that performs digital signal processing of wavelength lock processing, and the result is output to the wavelength control circuit 3.

In the second embodiment, the digital signal processing necessary for both the wavelength lock control and the low frequency signal control is realized by the common digital signal processing unit 20, so that it is simple without affecting the wavelength lock control. it is possible to adjust the amplitude of the laser light generated by a high-precision low-frequency signal Do configuration.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. In the above-described first embodiment, the signals output from the PDs 13 and 14 are branched and used for both wavelength lock control and low-frequency signal control. However, in the third embodiment, the PDs 13 and 14 are used. The obtained signal is branched and output in a time division manner to the wavelength lock control and the low frequency signal control.

  FIG. 3 is a block diagram showing a configuration of a laser apparatus including a laser modulation wave adjusting apparatus according to Embodiment 3 of the present invention. In FIG. 3, this laser device is provided with new switches 31 and 32 at the subsequent stage of PDs 13 and 14, and the signals acquired by PDs 13 and 14 under the control of timer 30 Each of the filters 15 and 16 is time-divisionally output. Other configurations are the same as those of the first embodiment, and the same reference numerals are given to the same components. In FIG. 3, an analog circuit is shown corresponding to the first embodiment. However, the present invention is not limited to this, and the configuration from the PDs 13 and 14 to the comparators 5 and 17 may be configured by a digital circuit.

  The time division time is assigned to the switches 31 and 32. For example, when the low-frequency signal is a dither signal for suppressing SBS, it is set to 30 seconds on the comparator 5 side and 5 seconds on the comparator 17 side, for example. Time-sharing control should be performed.

  In the third embodiment, the switches 31 and 32 are used to control the wavelength lock control and the low frequency signal control in a time-sharing manner. Therefore, the wavelength lock control and the low frequency signal control are performed with importance. It can be flexibly assigned and controlled accordingly. For example, when the low-frequency signal control is performed slowly with a secular change, an extremely short time may be allocated to the low-frequency signal control.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, a multiplier is provided, and this multiplier synchronizes the output on the wavelength locker side with the low frequency signal to detect low frequency fluctuations.

  4 is a block diagram showing a configuration of a laser apparatus including a laser modulation wave adjusting apparatus according to Embodiment 4 of the present invention. In FIG. 4, multipliers 33 and 34 are provided in the subsequent stages of PDs 13 and 14, respectively. The outputs of the multipliers 33 and 34 are input to the low frequency control circuit 6, and the low frequency control circuit 6 outputs the adjusted low frequency signal f to the LD 1 and to the multipliers 33 and 34. The multipliers 33 and 34 multiply the PDs 13 and 14 and the output from the low frequency control circuit 6, respectively, and output the result to the low frequency control circuit 6. Other configurations are the same as those of the first embodiment, and the same reference numerals are given to the same components.

  That is, in the fourth embodiment, the processing of the comparator 5 is performed using the multipliers 33 and 34. Thus, the low frequency signal can be adjusted with a simpler configuration.

(Embodiment 5)
Next, a fifth embodiment of the present invention will be described. In each of the first to fourth embodiments described above, the low frequency signal is a single signal, and the low frequency signal such as path information is superimposed and transmitted, and this low frequency signal is used as a dither signal for SBS suppression. However, in the fourth embodiment, a low frequency signal such as path information and a dither signal for SBS suppression are generated or input as different low frequency signals, and these are superimposed and output on the laser beam.

  FIG. 5 is a block diagram showing a configuration of a laser apparatus including a laser modulation wave adjusting apparatus according to Embodiment 5 of the present invention. In FIG. 5, the laser device 40 outputs a signal output from the external low frequency information generation unit 41, for example, a low frequency signal f <b> 1 indicating path information, to the amplitude adjuster 43 via the interface 42. The amplitude adjuster 43 controls the amplitude of the input low frequency signal f1 and outputs it to the adder 47.

  On the other hand, the amplitude adjuster 45 adjusts the amplitude of the low frequency signal f2 output from the clock generator 44 based on the adjustment control signal output from the low frequency control circuit 6 and outputs the adjusted signal to the adder 47. .

  The adder 47 adds the low-frequency signals f1 and f2, and outputs the added signal to the bias controller (APC) 48. The APC 48 modulates the injected current signal to the LD 1 with the added signal.

  Here, the LD degradation estimation unit 46 stores the contents of the amplitude adjusted by the low frequency control circuit 6, the time of the amplitude adjustment, and the fluctuation of the bias current added with the low frequency signal as a history. And the degradation of LD1 is estimated. Furthermore, the LD degradation estimation unit 46 controls the amplitude adjuster 43 to perform amplitude adjustment on the low frequency signal f1 based on the estimated degradation of the LD1.

  By providing the LD degradation estimation unit 46, it is possible to adjust the amplitude of the low-frequency signal f1 only by adjusting the amplitude of the low-frequency signal f2 performed by effectively using the wavelength locker control. As a result, the low-frequency signals f1 and f2, which are two different superimposed signals, can be adjusted with a simple configuration.

  In the first to fourth embodiments described above, a signal such as path information is also used as a dither signal. However, only a low frequency signal as a dither signal or only a low frequency signal such as path information is adjusted. It may be.

As described above, the laser modulation wave adjustment device according to the invention, the width adjustment vibration for the low-frequency signal superimposed on the laser light, by effectively utilizing the wavelength locking function reliably low frequency signal with a simple configuration since the width adjustment oscillation can be performed, suitable for WDM communication systems.

It is a block diagram which shows the structure of the laser apparatus containing the laser modulation wave adjustment apparatus which is Embodiment 1 of this invention. It is a block diagram which shows the structure of the laser apparatus containing the laser modulation wave adjustment apparatus which is Embodiment 2 of this invention. It is a block diagram which shows the structure of the laser apparatus containing the laser modulation wave adjustment apparatus which is Embodiment 3 of this invention. It is a block diagram which shows the structure of the laser apparatus containing the laser modulation wave adjustment apparatus which is Embodiment 4 of this invention. It is a block diagram which shows the structure of the laser apparatus containing the laser modulation wave adjustment apparatus which is Embodiment 5 of this invention.

Explanation of symbols

1 Laser diode (LD)
2 Wavelength locker 3 Wavelength control circuit 4 Peltier element 5, 17, 25, 27 Comparator 6 Low frequency control circuit 11 Mirror 12 Optical filter 13, 14 Photodiode (PD)
15, 16 Low-pass filter 20 Digital signal processing unit 21 High-speed sampling unit 22, 23 Sample acquisition circuit 30 Timer 31, 32 Switch 33, 34 Multiplier 41 Low-frequency information generation unit 42 Interface 43, 45 Amplitude adjuster 44 Clock generation unit 46 LD degradation estimation unit 47 Adder 48 Bias controller (APC)

Claims (5)

The light monitored from the laser diode is branched, one branched light is received by the first light receiving element, the other branched light is filtered with a predetermined wavelength component and received by the second light receiving element, Performs wavelength lock control of laser light output from the laser diode based on values received by the first and second light receiving elements, and adjusts a laser modulation wave to output a predetermined low frequency signal superimposed on the laser light In the device
Obtaining means for said first and second light receiving elements to obtain the amplitude displacement of the laser light generated by said predetermined low-frequency signal superimposed on the laser light based on the value of the received light,
Based on the amplitude displacement of which has been acquired by the acquisition unit, the laser diode by changing the amplitude of the predetermined low frequency signal input to the amplitude displacement of the laser light generated by said predetermined low frequency signal Adjusting means for adjusting to a certain level;
A laser-modulated wave adjusting device comprising: The light monitored from the laser diode is branched, one branched light is received by the first light receiving element, the other branched light is filtered with a predetermined wavelength component and received by the second light receiving element, Based on the values received by the first and second light receiving elements, the wavelength lock control of the laser light output from the laser diode is performed, and the first low frequency signal and the second low frequency signal are superimposed on the laser light. In the laser modulation wave adjusting device that outputs as
Wherein the first and second acquisition means for receiving elements to obtain the amplitude displacement of the laser light generated by said first and / or second low-frequency signal superimposed on the laser light based on the value of the received light When,
Based on the amplitude displacement of which has been acquired by the acquisition unit, the laser diode by changing the amplitude of the predetermined low frequency signal inputted to the laser generated by said first and / or second low-frequency signal and adjusting means for adjusting the amplitude displacement of the optical constant,
A laser-modulated wave adjusting device comprising: Sampling means for high-speed sampling of values received by the first and second light receiving elements;
Said acquisition means, acquires the amplitude displacement of the predetermined low frequency signal, the first low-frequency signal or the second low-frequency signal, using a part or all of the data sampled by said sampling means The laser modulation wave adjusting device according to claim 1 or 2, wherein First and second switches provided at a subsequent stage of the first and second light receiving elements;
Time-division control means for time-division controlling switching of the first and second switches;
The laser-modulated wave adjusting device according to claim 1, further comprising: Deterioration estimating means for estimating deterioration of the laser diode based on the adjustment history of the first low-frequency signal to be adjusted by the adjusting means;
Deterioration adjusting means for adjusting the second low-frequency signal using the estimation result of the deterioration estimating means;
The laser-modulated wave adjusting device according to any one of claims 2 to 4 , further comprising:

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