JP6046071B2 - Control device and control method for wavelength tunable light source - Google Patents

Description

  The present invention relates to a control device and a control method for a wavelength tunable light source.

  As a method of controlling a wavelength tunable light source that can change the laser oscillation wavelength by temperature control, such as a semiconductor laser element, the wavelength of the laser beam and the temperature of the wavelength tunable light source are monitored, and the wavelength of the laser beam is determined based on the monitoring result. A technique for controlling to a desired value is disclosed (for example, see Patent Documents 1 and 2).

  In Patent Document 1, in order to stabilize the wavelength of the laser beam output from the laser element, the deviation of the laser beam wavelength from the target value and the deviation of the laser element temperature from the target value are monitored as control deviations. A technique is disclosed in which one of two control deviations is selected based on a condition monitoring result, and the temperature of the laser element is controlled so that the selected control deviation is reduced.

  In Patent Document 2, a wavelength drift is achieved by switching between a control unit that sets a predetermined peak among a plurality of peaks that serve as a wavelength reference in a wavelength reference device and a control unit that stabilizes the wavelength using the set peak as a wavelength reference. There is disclosed a technique that is capable of stabilizing the wavelength with high stability.

Japanese Patent No. 4124845 Japanese Patent No. 2520740

  However, in the configurations of Patent Documents 1 and 2 described above, when the control parameters (temperature and wavelength) deviate from the controllable range for some reason, or when an abnormality such as a failure occurs in the control means, normal control is performed. There is a problem that it may not be possible.

  The present invention has been made in view of the above, and an object of the present invention is to provide a control device and a control method for a wavelength tunable light source that can perform normal control more stably.

  In order to solve the above-described problems and achieve the object, a wavelength tunable light source control device according to the present invention is a wavelength tunable light source control device capable of changing a laser oscillation wavelength by temperature control, and A temperature monitoring unit that monitors temperature, a temperature comparison unit that compares the monitored temperature with a target temperature, and outputs the result as a temperature monitor feedback control value, and monitors the wavelength of the laser light output from the wavelength light source A wavelength monitor unit, a wavelength comparison unit that compares the monitored wavelength with a target wavelength and outputs the result as a wavelength monitor feedback control value, and a feedforward control of a target control value for temperature control of the wavelength variable light source Current target value input unit that outputs as a value, the temperature monitor feedback control value, the wavelength monitor feedback control value, and The feedforward control value is input, a control method selection unit that selectively switches and outputs one of the three control values, and the selectively output control value is input and the input control A temperature control unit that controls the temperature of the wavelength tunable light source according to a value, and a main control unit that controls the selective output of the control method selection unit.

  The control apparatus for a wavelength tunable light source according to the present invention, in the above invention, the main control unit, when the control method selection unit switches the output between the temperature monitor feedback control value and the wavelength monitor feedback control value, Control is performed so that the output is switched after the feedforward control value is selectively output.

  The control apparatus for a wavelength tunable light source according to the present invention provides a monitor abnormality in the wavelength monitor unit or the temperature monitor related to the control value after switching when the control value selectively output by the control method selection unit is switched in the above invention. A wavelength monitor abnormality detecting unit or a temperature monitor abnormality detecting unit for detecting the temperature before switching.

  When the wavelength monitor abnormality detecting unit or the temperature monitor abnormality detecting unit detects a monitor abnormality in the above-described invention, the main control unit is configured to control the control method selection unit. Is controlled to selectively output the feedforward control value.

  In the control apparatus for a wavelength tunable light source according to the present invention, in the above invention, the target control value is a value corresponding to a control value before switching immediately before the selective output of the feedforward control value or a predetermined value. It is characterized by being.

  A wavelength tunable light source control method according to the present invention is a wavelength tunable light source control method capable of changing a laser oscillation wavelength by temperature control, the temperature monitoring step of monitoring the temperature of the wavelength tunable light source, and the monitored temperature. A temperature comparison step of comparing the target temperature and outputting the result as a temperature monitor feedback control value; a wavelength monitoring step of monitoring the wavelength of the laser beam output from the wavelength light source; and the monitored wavelength and the target wavelength. A wavelength comparison step for comparing and outputting the result as a wavelength monitor feedback control value; a current target value input step for outputting a target control value for temperature control of the wavelength tunable light source as a feedforward control value; and the temperature monitor The feedback control value, the wavelength monitor feedback control value, and the feedforward control value A control mode selection step of selecting one, characterized in that it comprises a temperature adjustment step of adjusting the temperature of the wavelength tunable light source according to the selected control value.

  According to the present invention, there is an effect that it is possible to realize a control device and a control method for a wavelength tunable light source that can perform more stable and normal control.

FIG. 1 is a block diagram illustrating a configuration of a wavelength tunable laser device according to an embodiment. FIG. 2 is a flowchart showing a control example 1 of the wavelength tunable laser element in the wavelength tunable laser apparatus shown in FIG. FIG. 3 is a flowchart showing a control example 2 of the wavelength tunable laser element in the wavelength tunable laser apparatus shown in FIG. FIG. 4 is a flowchart showing a control example 3 of the wavelength tunable laser element in the wavelength tunable laser apparatus shown in FIG. FIG. 5 is a flowchart showing a control example 4 of the wavelength tunable laser element in the wavelength tunable laser apparatus shown in FIG.

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

(Embodiment)
FIG. 1 is a block diagram showing a configuration of a wavelength tunable laser device according to an embodiment of the present invention. As shown in FIG. 1, the wavelength tunable laser device 100 includes a laser module 10 and a control device 20 that controls the laser module 10.

  The laser module 10 includes a semiconductor laser element 11, an optical coupler 12, a temperature sensitive element 13, and a cooling heating element 14.

  The semiconductor laser element 11 is a laser diode (LD) and is a wavelength tunable light source that can change the laser oscillation wavelength by temperature control. The semiconductor laser element 11 outputs laser light L1 having a wavelength (for example, a wavelength of 1530 nm to 1610 nm) used for optical communication, for example.

  The optical coupler 12 receives the laser light L1, outputs most of the light intensity as laser light L2 to the outside of the wavelength tunable laser device 100, and the remaining part (for example, 1% to 5%) of the monitor light L3. , L4 is output to the control device 20 of the wavelength tunable laser device 100.

  The temperature-sensitive element 13 is, for example, a thermistor or a thermocouple, and is an element that is disposed in the vicinity of the semiconductor laser element 11 and monitors the temperature of the semiconductor laser element 11. The cooling heating element 14 is composed of, for example, an electronic cooling element such as a Peltier element and a heater, and is disposed in the vicinity of the semiconductor laser element 11 to control the temperature of the semiconductor laser element 11.

  Next, the control device 20 will be described. The control device 20 includes a temperature monitor circuit 21a that constitutes a temperature monitor unit, a temperature monitor abnormality detection circuit 21b that is a temperature monitor abnormality detection unit, a laser temperature target value input unit 21c, and a comparison unit 21d that is a temperature comparison unit. The wavelength reference unit 22a and the wavelength monitor circuit 22b constituting the wavelength monitor unit, the wavelength monitor abnormality detection circuit 22c as the wavelength monitor abnormality detection unit, the wavelength target value input unit 22d, and the comparison unit 22e as the wavelength comparison unit The current target value input unit 23, a control method selection circuit 24 that is a control method selection unit, a current control circuit 25 that constitutes a temperature control unit, and a controller 26 that is a main control unit.

First, the configuration and operation related to the temperature monitor will be described.
The temperature monitor circuit 21 a is connected to the temperature sensing element 13, monitors the temperature of the semiconductor laser element 11 based on the input from the temperature sensing element 13, compares the value indicating the monitor temperature with the comparison unit 21 d, and detects temperature monitor abnormality. Output to the circuit 21b. The laser temperature target value input unit 21c sets a laser temperature target value (target temperature) based on a command from the controller 26 described later, and outputs the laser temperature target value to the comparison unit 21d. The comparison unit 21d compares the target temperature input from the laser temperature target value input unit 21c with the monitor temperature corresponding to the input value from the temperature monitor circuit 21a, and selects the control method as the temperature monitor feedback control value. Output to the circuit 24.

  On the other hand, the temperature monitor abnormality detection circuit 21 b detects a temperature monitor abnormality from the value input from the temperature monitor circuit 21 a and outputs it to the controller 26.

Next, the configuration and operation related to the wavelength monitor will be described.
The wavelength reference unit 22a receives the monitor light L3 from the optical coupler 12, and outputs the monitor light L5 corresponding to the wavelength of the monitor light L3. The wavelength reference device 22a is, for example, an etalon filter. When the monitor light L3 is input, the light intensity of the monitor light L3 is attenuated according to the wavelength discrimination characteristic and output as the monitor light L5.

  The wavelength monitor circuit 22b compares the intensity of the monitor light L4 and L5 received by the light receiver that receives the monitor lights L4 and L5, respectively, by taking the ratio of these, and based on the comparison result The wavelength of the laser light L1 is monitored, and a value indicating the monitor wavelength (for example, the intensity ratio between the monitor light L5 and the monitor light L4) is output to the comparison unit 22e and the wavelength monitor abnormality detection circuit 22c. The wavelength reference device 22a and the wavelength monitor circuit 22b constitute a so-called wavelength locker.

  The wavelength target value input unit 22d sets a wavelength target value (target wavelength) based on a command from the controller 26, and outputs it to the comparison unit 22e. The comparison unit 22e compares the target wavelength input from the wavelength target value input unit 22d with the monitor wavelength corresponding to the input value from the wavelength monitor circuit 22b, and uses the result as a wavelength monitor feedback control value as a control method selection circuit. 24.

  On the other hand, the wavelength monitor abnormality detection circuit 22c detects a wavelength monitor abnormality from the value input from the wavelength monitor circuit 22b and outputs it to the controller 26.

  Further, the current target value input unit 23 sets a current target value that is a target control value for temperature control of the semiconductor laser element 11 based on a command from the controller 26, and controls this as a feedforward control value. The data is output to the system selection circuit 24.

  The control method selection circuit 24 receives the temperature monitor feedback control value, the wavelength monitor feedback control value, and the feedforward control value. The control method selection circuit 24 selectively switches and outputs one of the three control values based on a command from the controller 26.

  The current control circuit 25 receives the selected control value from the control method selection circuit 24 and supplies the cooling heating element 14 with a current having a value corresponding to the control value. Thereby, the cooling heating element 14 heats or cools the semiconductor laser element 11 and controls it to a predetermined temperature.

  The controller 26 controls the control method selection circuit 24 and supplies drive current to the semiconductor laser element 11.

  Note that the temperature monitor circuit 21a, the temperature monitor abnormality detection circuit 21b, the wavelength monitor circuit 22b, and the wavelength monitor abnormality detection circuit 22c can be configured by analog circuits, for example. The laser temperature target value input unit 21c, the comparison unit 21d, the wavelength target value input unit 22d, the comparison unit 22e, the current target value input unit 23, the control method selection circuit 24, the current control circuit 25, and the controller 26 are a single unit. Or it can comprise a plurality of microcontrollers.

  Next, a method for controlling the laser module 10 by the control device 20 in the wavelength tunable laser device 100 will be described.

  First, the controller 26 supplies a drive current to the semiconductor laser element 11. As a result, the semiconductor laser element 11 outputs laser light L1 having a predetermined laser oscillation wavelength.

  Next, the temperature monitor circuit 21a monitors the temperature of the semiconductor laser element 11 based on the input from the temperature sensing element 13, and outputs a value indicating the monitor temperature to the comparison unit 21d and the temperature monitor abnormality detection circuit 21b. When the temperature monitor circuit 21a is constituted by an analog circuit, the monitor temperature is input after AD conversion is performed by an AD converter built in the comparison unit 21d or the temperature monitor abnormality detection circuit 21b or provided separately. . The laser temperature target value input unit 21c sets a laser temperature target value (target temperature) based on a command from the controller 26, and outputs it to the comparison unit 21d. The laser temperature target value input unit 21c sets a target temperature using calculation or table data stored therein. Here, the target temperature is the temperature of the semiconductor laser element 11 when the laser beam L1 has a target wavelength.

  Next, the comparison unit 21d compares the target temperature with the monitor temperature corresponding to the input value, and outputs the result to the control method selection circuit 24 as a temperature monitor feedback control value. Specifically, the comparison unit 21d calculates a deviation between the target temperature and the monitor temperature, and outputs a control value such that the deviation approaches zero as a temperature monitor feedback control value.

  On the other hand, the wavelength monitor circuit 22b monitors the laser light L1 based on the monitor light L4 and L5 input from the optical coupler 12 and the wavelength reference device 22a, and compares the value corresponding to the monitor wavelength with the comparison unit 22e and the wavelength monitor abnormality detection circuit. To 22c. When the wavelength monitor circuit 22b is formed of an analog circuit, the monitor wavelength is input after AD conversion is performed by an AD converter built in the comparison unit 22e or the wavelength monitor abnormality detection circuit 22c or provided separately. . The wavelength target value input unit 22d sets the target wavelength of the laser light L1 based on a command from the controller 26, and outputs the target wavelength to the comparison unit 22e.

  Next, the comparison unit 22e compares the target wavelength with the monitor wavelength corresponding to the input value, and outputs the result to the control method selection circuit 24 as a wavelength monitor feedback control value. Specifically, the comparison unit 22e calculates a deviation between the target wavelength and the monitor wavelength, and outputs a control value such that the deviation approaches zero as a wavelength monitor feedback control value.

  On the other hand, the current target value input unit 23 sets a current target value as a feedforward control value based on a command from the controller 26, and outputs it to the control method selection circuit 24. The current target value input unit 23 sets the current target value using calculation or table data stored therein. This feedforward control value is a control value for realizing the temperature of the semiconductor laser element 11 when the laser beam L1 has the target wavelength.

  Next, the control method selection circuit 24 selectively selects one of the three control values of the temperature monitor feedback control value, the wavelength monitor feedback control value, and the feedforward control value based on the command from the controller 26. Switch to output.

  Next, the current control circuit 25 receives the selected control value from the control method selection circuit 24, and supplies the cooling heating element 14 with a current having a value corresponding to the control value. Here, when the control value is the temperature monitor feedback control value, the current value applied to the cooling heating element 14 is feedback control of the temperature of the semiconductor laser element 11 so that the deviation between the target temperature and the monitor temperature approaches zero. Current value for When the control value is the wavelength monitor feedback control value, the current value given to the cooling heating element 14 feedback-controls the temperature of the semiconductor laser element 11 so that the deviation between the target wavelength and the monitor wavelength approaches zero. Current value. When the control value is a feedforward control value, the current value applied to the cooling heating element 14 is feedforward controlled to the temperature of the semiconductor laser element 11 when the laser light L1 has a target wavelength. Current value.

  In the tunable laser apparatus 100 according to the present embodiment, one of the three control values of the temperature monitor feedback control value, the wavelength monitor feedback control value, and the feedforward control value is selected, and the temperature of the semiconductor laser element 11 is set. I try to control it. As a result, even when there is an abnormality in one of the control units, for example, other normal control can be selected and performed without being affected by it, and for example, control runaway can be prevented. In particular, for feedforward control, a constant target current value can be directly given to the current control circuit 25 regardless of the state of the monitor circuit, so that an unstable state of control is less likely to occur than with other feedback control. . As a result, in the wavelength tunable laser device 100 according to the present embodiment, stable and normal control of the wavelength of the laser light L1 of the semiconductor laser element 11 can be performed.

  When the temperature monitor abnormality detection circuit 21b detects a temperature monitor abnormality from the value input from the temperature monitor circuit 21a, it outputs a signal indicating abnormality detection to the controller 26. The temperature monitoring abnormality is, for example, a case where the monitored temperature is out of a controllable range (normal range). Here, the normal range may be set, for example, from 20 ° C. to 60 ° C., which is the temperature control range of the semiconductor laser element 11, or from −10 ° C., which is the output range of the temperature monitor circuit 21a determined at the time of design. You may set to 90 degreeC etc. And the controller 26 may control the control system selection circuit 24, and may select and output a feedforward control value, when the signal which shows temperature monitoring abnormality is input.

  When the wavelength monitor abnormality detection circuit 22c detects a wavelength monitor abnormality from the value input from the wavelength monitor circuit 22b, it outputs a signal indicating abnormality detection to the controller 26. The wavelength monitoring abnormality is, for example, a case where the monitored wavelength is out of a controllable range (normal range). Here, the normal range may be set from 0.2 to 0.8, which is a wavelength monitor range determined by the extinction ratio of the wavelength reference device 22a, or the output of the wavelength monitor circuit 22b determined at the time of design. You may set to 0.01-5 etc. which are the range. Then, when a signal indicating a wavelength monitor abnormality is input, the controller 26 may control the control method selection circuit 24 to select and output a feedforward control value.

  Hereinafter, a control example of the semiconductor laser element 11 in the wavelength tunable laser device 100 according to the present embodiment will be described.

(Control example 1)
FIG. 2 is a flowchart showing a control example 1 of the semiconductor laser element 11 in the wavelength tunable laser device 100.

  First, in step S101, the control method selection circuit 24 selects a temperature monitor feedback control value and outputs it to the current control circuit 25, whereby the control device 20 performs temperature monitor feedback control.

  Next, in step S102, the controller 26 checks whether or not there is a request to switch the monitor circuit due to an external factor such as a command by an external signal. Here, the external factor is, for example, a light-on command or a wavelength stabilization control command. The light-on command is a command for causing the controller 26 to supply a drive current to the semiconductor laser element 11 and outputting the laser light L1 from the semiconductor laser element 11. Since this command outputs the laser beam L1, wavelength monitor feedback control becomes possible. The wavelength stabilization control command is a command for causing the control device 20 to perform wavelength monitor feedback control.

  When there is no request | requirement (step S102, No), temperature monitor feedback control is performed continuously. When there is a request (step S102, Yes), the controller 26 controls the control method selection circuit 24 so that the control method selection circuit 24 selects the feedforward control value and outputs it to the current control circuit 25. Thereby, the control apparatus 20 performs feedforward control (current instruction value feedforward control) (step S103).

  Next, in step S104, the controller 26 confirms whether or not there is a wavelength monitoring abnormality (normal or not) by inputting a signal from the wavelength monitoring abnormality detection circuit 22c. If normal (step S104, Yes), the controller 26 controls the control method selection circuit 24 so that the control method selection circuit 24 selects the wavelength monitor feedback control value and outputs it to the current control circuit 25. Thereby, the control device 20 performs wavelength monitor feedback control (step S105). When it is not normal (step S104, No), it returns to step S103 and the control apparatus 20 performs electric current instruction value feedforward control.

  In this control example 1, when the control is switched from the temperature monitor feedback control to the wavelength monitor feedback control (that is, the output of the current control circuit 25 is switched from the temperature monitor feedback control value to the wavelength monitor feedback control value), the feedforward control value Is output and current instruction value feedforward control is performed, and then switching is performed. As described above, the control is prevented from becoming unstable by performing the current instruction value feedforward control that directly gives a constant target current value to the current control circuit 25 at the time of switching. Furthermore, discontinuous processing such as monitoring circuit abnormality detection and circuit state adjustment can be performed during the current instruction value feedforward control.

(Control example 2)
FIG. 3 is a flowchart showing a control example 2 of the semiconductor laser element 11 in the wavelength tunable laser device 100.

  First, in step S201, the control device selection circuit 24 selects a wavelength monitor feedback control value and outputs it to the current control circuit 25, whereby the control device 20 performs wavelength monitor feedback control.

  Next, in step S202, the controller 26 checks whether or not there is a request to switch the monitor circuit due to an external factor such as a command by an external signal. Here, the external factors are, for example, a light off command, a wavelength abnormality, a light output abnormality, and a temperature abnormality. The light off command is a command for causing the controller 26 to stop supplying the drive current to the semiconductor laser element 11. Since this command stops the output of the laser beam L1, wavelength monitor feedback control becomes impossible. Further, the wavelength abnormality, the light output abnormality, or the temperature abnormality is a state in which the wavelength of the laser light L1, the intensity of the laser light, or the temperature of the semiconductor laser element 11 is outside the controllable range, and the wavelength monitor abnormality is detected. It is detected by the circuit 22c or the temperature monitor abnormality detection circuit 21b.

  When there is no request (step S202, No), the wavelength monitor feedback control is continued. When there is a request (step S202, Yes), the controller 26 controls the control method selection circuit 24 so that the control method selection circuit 24 selects the feedforward control value and outputs it to the current control circuit 25. Thus, the control device 20 performs current instruction value feedforward control (step S203).

  Next, in step S204, the controller 26 confirms whether or not there is a temperature monitoring abnormality by inputting a signal from the temperature monitoring abnormality detecting circuit 21b. If normal (step S204, Yes), the controller 26 controls the control method selection circuit 24 so that the control method selection circuit 24 selects the temperature monitor feedback control value and outputs it to the current control circuit 25. Thereby, the control device 20 performs temperature monitor feedback control (step S205). When it is not normal (step S204, No), it returns to step S203 and the control apparatus 20 performs electric current instruction value feedforward control.

  In this control example 2, when the control is switched from the wavelength monitor feedback control to the temperature monitor feedback control, the feed forward control value is output and the current instruction value feed forward control is performed, and then the switching is performed. This prevents the control from becoming unstable as in Control Example 1. Furthermore, discontinuous processing can be performed while performing the current instruction value feedforward control.

(Control example 3)
FIG. 4 is a flowchart showing a control example 3 of the semiconductor laser element 11 in the wavelength tunable laser device 100.

  First, in step S301, the control device 20 performs temperature monitor feedback control.

  Next, in step S302, the controller 26 checks whether or not there is a request to switch the monitor circuit. If there is no request (step S302, No), the temperature monitor feedback control is continued. If there is a request (step S302, Yes), step S303 is performed. In step S303, the controller 26 confirms whether there is any wavelength monitor abnormality by inputting a signal from the wavelength monitor abnormality detection circuit 22c.

  If it is normal (step S303, Yes), the control device 20 performs wavelength monitor feedback control (step S304). If not normal (step S303, No), step S305 is performed. In step S305, the controller 26 determines whether or not to continue the temperature monitor feedback control (whether or not to continue using the temperature monitor circuit 21a). For example, in a transient state from light-off to light-on, there is a possibility that the wavelength monitor circuit 22b is determined to be abnormal because a sufficient amount of light does not enter the wavelength monitor circuit 22b. Further, the wavelength monitor circuit 22b may be temporarily determined to be abnormal due to noise. Therefore, it is necessary to perform a normal check by the wavelength monitor abnormality detection circuit 22c for a certain period of time. If there is a wavelength monitoring abnormality even after a certain period of time has elapsed, it may be determined that the temperature monitoring circuit 21a should be used continuously.

  When continuing (step S305, Yes), it returns to step S301 and performs temperature monitor feedback control continuously. When not continuing (step S305, No), the control apparatus 20 performs electric current command value feedforward control (step S306), and returns to step S303 after that.

  In this control example 3, when the control is switched from the temperature monitor feedback control to the wavelength monitor feedback control, the monitor wavelength abnormality of the switching destination wavelength is confirmed, and if it is abnormal, the temperature monitor feedback control is continuously performed. Or whether to switch to current instruction value feedforward control. This more reliably prevents the control from becoming unstable. Furthermore, discontinuous processing such as monitoring circuit abnormality detection and circuit state adjustment can be performed during the current instruction value feedforward control.

(Control example 4)
FIG. 5 is a flowchart showing a control example 4 of the semiconductor laser element 11 in the wavelength tunable laser device 100.

  First, in step S401, the control device 20 performs wavelength monitor feedback control.

  Next, in step S402, the controller 26 confirms whether there is a request to switch the monitor circuit. When there is no request (step S402, No), the wavelength monitor feedback control is continued. When there is a request (step S402, Yes), the controller 26 confirms whether or not there is a temperature monitor abnormality by inputting a signal from the temperature monitor abnormality detection circuit 21b.

  When it is normal (step S403, Yes), the control device 20 performs temperature monitor feedback control (step S404). If not normal (step S403, No), step S405 is performed. In step S405, the controller 26 determines whether or not to continue the wavelength monitor feedback control.

  When continuing (step S405, Yes), it returns to step S401 and performs wavelength monitor feedback control continuously. When not continuing (step S405, No), the control apparatus 20 performs electric current command value feedforward control (step S406), and returns to step S403 after that. For example, when the request for switching in step S402 is caused by a wavelength abnormality, a light output abnormality, or the like, it is preferable to perform the current instruction value feedforward control without continuing the wavelength monitor feedback control.

  In this control example 4, when the control is switched from the wavelength monitor feedback control to the temperature monitor feedback control, the monitor wavelength abnormality of the switching destination temperature is confirmed, and if it is abnormal, the wavelength monitor feedback control is continuously performed. Or whether to switch to current instruction value feedforward control. This more reliably prevents the control from becoming unstable. Furthermore, discontinuous processing can be performed while performing the current instruction value feedforward control.

  In the above control example, when there is a monitor abnormality of temperature or wavelength, when the current indication value feedforward control is performed by switching the control thereafter, the following is preferable. That is, since there is a current value that the current control circuit 25 gave to the cooling heating element 14 in the feedback control before switching (that is, selective output of the feedforward control value), the current value immediately before switching is maintained. It is preferable to set a current target value corresponding to the above and perform current instruction value feedforward control. Further, when the ambient temperature changes while the current instruction value feedforward control is being performed, the temperature adjustment of the semiconductor laser element 11 becomes inappropriate due to excess or deficiency of the current value applied to the cooling heating element 14, and deterioration or the like occurs. there's a possibility that. In order to prevent this, the current target value may be set to a predetermined value, for example, 0 mA. Further, if the temperature or wavelength monitoring abnormality continues for a certain period of time, the current target value may be forcibly changed to 0 mA. Further, in addition to the current of the cooling heating element 14, the driving current of the semiconductor laser element 11 may be set to a predetermined value.

  The present invention is not limited to the above embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

DESCRIPTION OF SYMBOLS 10 Laser module 11 Semiconductor laser element 12 Optical coupler 13 Temperature sensitive element 14 Cooling heating element 20 Control apparatus 21a Temperature monitor circuit 21b Temperature monitor abnormality detection circuit 21c Laser temperature target value input part 21d, 22e Comparison part 22a Wavelength reference device 22b Wavelength monitor Circuit 22c Wavelength monitor abnormality detection circuit 22d Wavelength target value input unit 23 Current target value input unit 24 Control method selection circuit 25 Current control circuit 26 Controller 100 Wavelength variable laser apparatus L1, L2 Laser light L3, L4, L5 Monitor light

Claims (3)

A control device for a wavelength tunable light source capable of changing a laser oscillation wavelength by temperature control,
A temperature monitor for monitoring the temperature of the wavelength tunable light source;
A temperature comparison unit that compares the monitored temperature with a target temperature and outputs the result as a temperature monitor feedback control value;
A wavelength monitor unit for monitoring the wavelength of the laser beam output from the wavelength light source;
A wavelength comparison unit that compares the monitored wavelength with a target wavelength, and outputs the result as a wavelength monitor feedback control value;
A current target value input unit that outputs a target control value for temperature control of the wavelength tunable light source as a feedforward control value;
The temperature monitor feedback control value, the wavelength monitor feedback control value, and the feedforward control value are input, and a control method selection unit that selectively switches and outputs one of the three control values;
Wavelength monitor abnormality detection unit or temperature monitor abnormality that detects a monitor abnormality in the wavelength monitor unit or temperature monitor unit related to the control value after switching when switching the control value selectively output by the control method selection unit A detection unit;
A temperature control unit that receives the selectively output control value and controls the temperature of the tunable light source according to the input control value;
A main control unit that controls the selective output of the control method selection unit ,
The main control unit selectively outputs the feedforward control value when the control method selection unit switches the output between the temperature monitor feedback control value and the wavelength monitor feedback control value. Control to switch,
The target control value, the control device of the variable wavelength light source, wherein the Ru value der corresponding to the control value before switching immediately before the selective output of the feed forward control value. When the wavelength monitor abnormality detection unit or the temperature monitor abnormality detection unit detects a monitor abnormality, the main control unit controls the control method selection unit to selectively output the feedforward control value. The control apparatus for a wavelength tunable light source according to claim 1 . A method of controlling a wavelength tunable light source capable of changing a laser oscillation wavelength by temperature control,
A temperature monitoring step of monitoring the temperature of the wavelength tunable light source;
A temperature comparison step of comparing the monitored temperature with a target temperature and outputting the result as a temperature monitor feedback control value;
A wavelength monitoring step of monitoring the wavelength of the laser beam output from the wavelength light source;
A wavelength comparison step of comparing the monitored wavelength with the target wavelength and outputting the result as a wavelength monitor feedback control value;
A current target value input step for outputting a target control value for temperature control of the wavelength tunable light source as a feedforward control value;
A control method selection step of selecting one of the temperature monitor feedback control value, the wavelength monitor feedback control value, and the feedforward control value;
Wavelength monitor abnormality detection step or temperature monitor abnormality that detects a monitor abnormality at the monitored wavelength or the monitored temperature related to the control value after the change when the control value output in the control method selection step is selectively switched A detection process;
A temperature adjustment step of adjusting the temperature of the wavelength tunable light source according to the selected control value;
When the output is switched between the temperature monitor feedback control value and the wavelength monitor feedback control value in the control method selection step, the feedforward control value is selectively output and then the output is switched. and a control step of, only including,
The method for controlling a wavelength tunable light source, wherein the target control value is a value corresponding to a control value before switching immediately before the selective output of the feedforward control value .

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