JP2009044141A - Optical device, and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device and a control method thereof, which ensure desired optical characteristics even when a heater deteriorates. <P>SOLUTION: The optical device includes an optical element (10) the temperature of which is controlled by a temperature controller (20) and having an optical waveguide the refractive index of which is controlled by means of a heater (14), a detecting section (17) for measuring a current flowing through the heater (14) and/or a voltage being applied to the heater, and a control section (50) for maintaining the power being supplied to the heater (14) at a constant level based on the measurements from the detecting section (17). The control method of the optical device controls the temperature of the optical element (10) having an optical waveguide, the refractive index of which is varied by means of the heater (14), by means of the temperature controller (20), and controls the power being supplied to the heater so as to be maintained at a constant level based on a current flowing through the heater (14) and/or a voltage being applied to the heater. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical device and a control method thereof.

  A wavelength tunable semiconductor laser is an example of the optical device. This wavelength tunable semiconductor laser has a gain function for laser oscillation and a wavelength selection function. As a method of selecting the wavelength, there is a method of changing the wavelength characteristic of loss / reflection or gain by changing the refractive index of an optical functional region such as a diffraction grating provided in the optical waveguide in the resonator.

  Here, the method of changing the refractive index is advantageous in terms of reliability, manufacturing cost, and the like because it does not require a mechanical movable part as compared with a method of changing the physical angle or length. . Examples of the method for changing the refractive index include a method for changing the temperature of the optical waveguide, a method for changing the carrier density in the optical waveguide by current injection, and the like. As a specific example of a wavelength tunable laser adopting a method of changing the temperature of the optical waveguide, for example, a partial grating mirror (SG-DBR) in which the peak wavelength of the reflection spectrum is periodically distributed, and There has been proposed a semiconductor laser or the like provided with a partial grating active region (SG-DFB) in which the peak wavelength of the gain spectrum is periodically distributed.

  In this semiconductor laser, by controlling the correlation between the reflection spectra of the partial diffraction grating mirror and the partial diffraction grating active region, wavelength selection using the vernier effect is performed and laser light is output. That is, this semiconductor laser oscillates at a wavelength having the highest reflection intensity among the wavelengths where the two spectra overlap. Therefore, the oscillation wavelength can be controlled by controlling the relative relationship between the two reflection spectra.

  Patent Document 1 discloses a semiconductor laser that controls the oscillation wavelength by controlling the refractive index of an optical waveguide. In Patent Document 1, a heater is employed as a means for controlling the refractive index of the optical waveguide, and wavelength control is realized by temperature control of the optical waveguide by the heater.

Japanese Patent Laid-Open No. 9-92934

  When a heater is used to control the refractive index of the optical waveguide, deterioration of the heater becomes a problem. That is, if the heater deteriorates and its resistance value changes, the amount of heat generated will change even if a constant current is supplied to the heater. In particular, in an optical device that exhibits a predetermined optical function by combining optical waveguides having different wavelength characteristics such as a combination of SG-DFB and SG-DBR, the temperature difference between the optical waveguides is important. Unexpected changes in calorific value are fatal.

  In addition, since the heater for controlling the temperature of such an optical waveguide has a calorific value (ΔT) of about 0 to 40 degrees and is a relatively low temperature as a heating element, until now, Deterioration was never considered.

  By the way, as a heater control method, a method of arranging a temperature detection element such as a thermistor in the vicinity of the optical waveguide and controlling the amount of heat generated by the heater from the detection result can be considered. The detection result of the temperature detection element is ideal because it takes into account the change in the temperature of the external environment and the change in the amount of heat generated by the deterioration of the heater.

  However, in order to realize this method, it is necessary to arrange a temperature detection element in the vicinity of the heater, and it is relatively difficult to employ the temperature detection element for a fine device such as a laser chip.

  An object of the present invention is to provide an optical device that can obtain desired optical characteristics even when a heater is deteriorated, and a control method thereof.

  An optical device according to the present invention includes an optical element having an optical waveguide whose refractive index is controlled by a heater, the temperature of which is controlled by a temperature control device, and a detector that measures a current flowing through the heater and / or a voltage applied to the heater. And a control unit that keeps constant power supplied to the heater based on the measurement result of the detection unit.

  In the optical device according to the present invention, the temperature change of the optical device is suppressed by using the temperature control device. That is, since the temperature change of the optical device due to the temperature change of the external environment can be ignored, the temperature of the optical waveguide is substantially determined by the amount of heat generated by the heater. On the other hand, the amount of heat generated by the heater is determined by the amount of power supplied to the heater. In this case, even if the heater is deteriorated and the resistance value of the heater is changed, the amount of heat generated by the heater is constant if the power amount of the heater is controlled to be constant. In the present invention, based on this consideration, the temperature of the optical element is controlled by the temperature control device so that the temperature of the optical waveguide can be substantially determined by the electric energy of the heater. And in order to specify the electric energy of a heater, the electric current which flows into a heater, and / or the voltage concerning a heater are detected. According to the present invention, the amount of electric power of the heater is specified, and the heater control is performed based on this amount of electric power. Therefore, even when the heater is deteriorated, the heat generation amount can be kept constant. Therefore, desired optical characteristics can be obtained.

  The detector may measure the voltage across the heater. The control unit controls the amount of current supplied to the heater, and obtains the power supplied to the heater based on the product of the measurement result of the voltage across the heater and the amount of current supplied to the heater. May be.

  A terminal for supplying a current to the heater, a terminal for grounding the heater, and a terminal for connecting to the heater separately from these terminals and for measuring a voltage applied to the heater by the voltage detector; Furthermore, you may provide. In this case, it is suppressed that the voltage drop resulting from resistance, such as a terminal and a wire, influences the detection result of a voltage detection part. Thereby, the accuracy of voltage detection by the voltage detection unit is improved.

  The optical element may be a wavelength tunable semiconductor laser. The optical element may include an active region including a diffraction grating, and an optical waveguide portion that is optically coupled to the active region and includes a diffraction grating, and an equivalent refractive index is changed by a heater. The diffraction grating in the active region and the optical waveguide portion may include a first region having the diffraction grating, and a second region connected to the first region and serving as a space portion.

  The optical element may include an active region and a pair of optical waveguide portions provided with optical coupling on both sides of the active region, at least one of which is provided with a heater to change the equivalent refractive index. The optical element may be a Mach-Zehnder optical switch in which at least one of the pair of optical waveguides is an optical waveguide whose refractive index is controlled by a heater. In the optical waveguide, the diffraction grating may not be provided in the region where the heater is provided.

  The method for controlling an optical device according to the present invention controls the temperature of an optical semiconductor element including an optical waveguide whose refractive index is controlled by a heater, based on a current flowing through the heater and / or a voltage applied to the heater. The power is controlled so that the power supplied to the heater is kept constant. In the optical device control method according to the present invention, the temperature change of the optical semiconductor element is suppressed by using the temperature control device. Furthermore, since the electric power supplied to the heater is kept constant, the amount of heat generated by the heater can be kept constant. In this case, desired light characteristics can be obtained even when the heater is deteriorated.

  The power may be controlled by controlling the current supplied to the heater based on the voltage applied to the heater. The optical element may be a wavelength tunable semiconductor laser. The optical element may include an active region including a diffraction grating, and an optical waveguide portion that is optically coupled to the active region and includes a diffraction grating, and an equivalent refractive index is changed by a heater. The diffraction grating in the active region and the optical waveguide portion may include a first region having the diffraction grating, and a second region connected to the first region and serving as a space portion.

  The optical element may include an active region and a pair of optical waveguide portions provided with optical coupling on both sides of the active region, at least one of which is provided with a heater to change the equivalent refractive index. The optical element may be a Mach-Zehnder optical switch in which at least one of the pair of optical waveguides is an optical waveguide whose refractive index is controlled by a heater. The optical length of the optical waveguide different from the design may be adjusted to the design optical length by controlling the refractive index of the optical waveguide with a heater.

  According to the present invention, desired light characteristics can be obtained even when the heater is deteriorated.

  Hereinafter, the best mode for carrying out the present invention will be described.

  First, an example using a semiconductor laser as an optical element will be described. FIG. 1 is a schematic diagram showing the overall configuration of a semiconductor laser 10 and a laser apparatus 100 having the same according to a first embodiment of the present invention. As shown in FIG. 1, the laser device 100 includes a semiconductor laser 10, a temperature control device 20, a wavelength detection unit 30, an output detection unit 40, and a controller 50. The semiconductor laser 10 is disposed on the temperature control device 20. Next, details of each part will be described.

  The semiconductor laser 10 has a structure in which an SG-DBR region 11, an SG-DFB region 12, and a semiconductor optical amplifier (SOA) region 13 are sequentially connected. The SG-DBR region 11 includes an optical waveguide in which gratings are provided at predetermined intervals. That is, the optical waveguide of the SG-DBR region 11 is provided with a first region having a diffraction grating and a second region connected to the first region and serving as a space portion. The optical waveguide of the SG-DBR region 11 is made of a semiconductor crystal whose absorption edge wavelength is shorter than the laser oscillation wavelength. A heater 14 is provided on the SG-DBR region 11.

  The SG-DFB region 12 includes an optical waveguide in which gratings are provided at predetermined intervals. That is, the optical waveguide of the SG-DFB region 12 is provided with a first region having a diffraction grating and a second region connected to the first region and serving as a space portion. The optical waveguide of the SG-DFB region 12 is made of a semiconductor crystal having a gain with respect to laser oscillation at a target wavelength. An electrode 15 is provided on the SG-DFB region 12. The SOA region 13 includes an optical waveguide made of a semiconductor crystal for gaining light by current control or for absorbing light. An electrode 16 is provided on the SOA region 13. Note that the optical waveguides of the SG-DBR region 11, the SG-DFB region 12, and the SOA region 13 are optically coupled to each other. In addition, the laser device 100 includes a voltage detection unit 17 that measures a voltage applied to the heater 14.

  The semiconductor laser 10 and the thermistor (not shown) are mounted on the temperature control device 20. The wavelength detection unit 30 includes a light receiving element that measures the intensity of the laser output light and a light receiving element that measures the intensity of the laser output light including the wavelength characteristics by transmitting the etalon. The output detection unit 40 includes a light receiving element that measures the intensity of laser output light that has passed through the SOA region 13. In FIG. 1, the wavelength detection unit 30 is disposed on the SG-DBR region 11 side and the output detection unit 40 is disposed on the SOA region 13 side. However, the configuration is not limited thereto. For example, each detection part may be arrange | positioned reversely.

  The controller 50 includes a control unit such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), a power source, and the like. The ROM of the controller 50 stores control information, control programs, and the like for the semiconductor laser 10. The control information is recorded in the lookup table 51, for example. An example of the lookup table 51 is shown in FIG.

As shown in FIG. 2, the look-up table 51 includes an initial setting value, a feedback control target value, and an alarm setting range for each channel. The initial setting value includes an initial current value _I LD of the SG-DFB region 12, an initial current value _{I SOA} of the SOA region 13, the initial temperature value _{T LD} of the initial current value _{I Heater} and temperature controller 20 of the heater 14 is . The feedback control target value includes the feedback control target value Im1 of the output detection unit 40, the feedback control target value Im3 / Im2 of the wavelength detection unit 30, and the feedback control target value P _Heater of the power supplied to the heater 14. The alarm setting range includes a resistance R _Heater (lower limit) that is a lower limit value of the electric resistance of the heater 14 and a resistance R _Heater (upper limit) that is an upper limit value.

Subsequently, a control method of the laser apparatus 100 will be described. FIG. 3 is a flowchart illustrating an example of a control method of the laser apparatus 100. As shown in FIG. 3, first, the controller 50 refers to the look-up table 51, and the initial current value I _LD , the initial current value I _SOA , the initial current value I _Heater, and the initial temperature value T corresponding to the set channel. _{An LD} is acquired (step S1).

Next, the controller 50 causes the semiconductor laser 10 to oscillate based on the initial setting value acquired in step S1 (step S2). Specifically, first, the controller 50 controls the temperature control device 20 so that the temperature of the temperature control device 20 becomes the initial temperature value _TLD . Thereby, the temperature of the semiconductor laser 10 is controlled to a constant temperature near the initial temperature value _TLD . As a result, the equivalent refractive index of the optical waveguide in the SG-DFB region 12 is controlled. Next, the controller 50 supplies a current having a magnitude of the initial current value I _Heater to the heater 14. Thereby, the equivalent refractive index of the optical waveguide in the SG-DBR region 11 is controlled to a predetermined value. Next, the controller 50 supplies a current having a magnitude of the initial current value I _LD to the electrode 15. Thereby, light is generated in the optical waveguide in the SG-DFB region 12. As a result, the light generated in the SG-DFB region 12 is repeatedly reflected and amplified by the optical waveguides in the SG-DBR region 11 and the SG-DFB region 12 to oscillate. Next, the controller 50 supplies a current having a magnitude of the initial current value _ISOA to the electrode 16. With the above control, the semiconductor laser 10 emits laser light to the outside with an initial wavelength corresponding to the set channel.

  Next, the controller 50 determines whether or not the wavelength of the emitted laser is within the specified range based on the detection result of the wavelength detection unit 30 (step S3). Specifically, first, the controller 50 acquires the feedback control target value Im3 / Im2 from the lookup table 51, and acquires the detection result ratio Im3 / Im2 of the two light receiving elements included in the wavelength detection unit 30, and the ratio It is determined whether Im3 / Im2 is within a predetermined range including the feedback control target value Im3 / Im2.

  If it is not determined in step S3 that the laser wavelength is within the specified range, the controller 50 corrects the temperature of the temperature control device 20 (step S6). In this case, the peak wavelength of the gain spectrum in the optical waveguide in the SG-DFB region 12 changes. Thereafter, the controller 50 executes Step S3 again. By this loop, feedback control is performed so that the wavelength of the laser is maintained at a desired constant value.

  When it is determined in step S3 that the wavelength of the laser is within the regulation, the controller 50 determines whether or not the light intensity of the laser beam is within the regulation (step S4). Specifically, the controller 50 acquires the feedback control target value Im1 from the lookup table 51 and the detection result Im1 of the light receiving element included in the output detection unit 40, and the detection result Im1 includes the feedback control target value Im1. It is determined whether it is within a predetermined range.

  If it is not determined in step S4 that the laser light intensity is within the specified range, the controller 50 corrects the current supplied to the electrode 16 (step S7). Thereafter, the controller 50 executes Step S4 again. By this loop, feedback control is performed so that the light intensity of the laser light is maintained at a desired constant value.

When it is determined in step S4 that the laser light intensity is within the regulation, the controller 50 determines whether the power supplied to the heater 14 is within the regulation (step S5). Specifically, the controller 50 obtains the feedback control target value P _Heater from the lookup table 51, and calculates the power supplied to the heater 14 from the detection result of the voltage detection unit 17 and the current value supplied to the heater 14. To do. The controller 50 determines whether or not the calculated value is within a predetermined range including the feedback control target value P _Heater .

  If it is not determined in step S5 that the power supplied to the heater 14 is within the specified range, the controller 50 corrects the power supplied to the heater 14 (step S8). In this case, the power can be corrected by correcting at least one of the current and the voltage. In the present embodiment, the controller 50 corrects the power by increasing or decreasing the current value supplied to the heater 14. By this loop, feedback control is performed so that the power supplied to the heater 14 is maintained at a desired constant value. In addition, when it determines with the electric power supplied to the heater 14 being in prescription | regulation in step S5, the controller 50 performs step S3 again.

  In the present embodiment, the temperature change of the semiconductor laser 10 is suppressed by using the temperature control device 20. Further, since the electric power supplied to the heater 14 is controlled to be kept at a constant value, even if the resistance of the heater 14 changes due to deterioration, the amount of heat generated by the heater 14 is kept constant. In this case, the temperature difference between the SG-DBR region 11 and the SG-DFB region 12 is kept constant. Thereby, the semiconductor laser 10 realizes a desired oscillation wavelength even when the heater 14 is deteriorated.

  In the present embodiment, it is possible to appropriately control the temperature of the optical waveguide without mounting the temperature detecting element on the semiconductor laser 10.

In the present embodiment, the voltage applied to the heater 14 is detected by the voltage detector 17. Further, the current supplied to the heater 14 is controlled to a predetermined value. Therefore, the resistance change of the heater 14 can be monitored using the voltage value and the current value. In this case, disconnection of the heater 14 and the possibility of disconnection can be determined. For example, the controller 50 may warn the user of a disconnection when the electrical resistance obtained from the detection result of the voltage detection unit 17 exceeds the resistance R _Heater (upper limit). In this case, the user can be prompted to replace the semiconductor laser 10.

The disconnection warning is effective for both deterioration of the heater 14 with time and sudden environmental changes. In particular, in a tunable laser such as the semiconductor laser 10, since a heater is provided in a minute region, unexpected stress may be applied to the heater due to manufacturing variations, usage environment, and the like. In such a case, the heater may deteriorate in a period shorter than the expected life. As a countermeasure in this case, the disconnection warning is effective. Further, the controller 50 may warn the user when the electrical resistance of the heater 14 falls below the resistance R _Heater (lower limit). In this case, an excessive current is suppressed from being supplied to the heater 14.

  Here, an example of the voltage detection unit 17 will be described. FIG. 4 is a diagram illustrating details of the voltage detection unit 17. As shown in FIG. 4, the voltage detection unit 17 includes a voltmeter 18, a terminal TVh, and a terminal TVhg. The terminal TVh is connected to the first end of the heater 14. The terminal TVhg is connected to the second end of the heater 14. The heater driving current from the controller 50 is supplied from the terminal TIh to the first end of the heater 14 and is grounded from the second end of the heater 14 through the terminal TIg.

  In such a configuration, no heater driving current flows between the terminal TVh and the terminal TVhg. In this case, it is suppressed that the voltage drop resulting from resistances, such as a terminal and a wire, affects the detection result of the voltmeter 18. Thereby, the voltage detector 17 can accurately detect the voltage applied to the heater 14.

  In this embodiment, the semiconductor laser in which the SG-DBR region and the SG-DFB region are combined has been described. However, the present invention is not limited to this. For example, the present invention may be applied to a semiconductor laser in which an active region serving as a gain portion is sandwiched between a pair of SG-DBR regions. In this case, a heater is provided in each SG-DBR region or on one side. In this case, if the voltage applied to the heater is detected by the voltage detection unit 17, feedback control can be performed so that the power supplied to the heater is constant.

  Further, the present invention can also be applied to a CSG-DBR (Chirped Sampled Distributed Distributed Bragg Reflector). Here, in the CSG-DBR, as compared with the SG-DBR, the interval between the space portions connecting the gratings is different. Thereby, the peak intensity in the reflection spectrum of CSG-DBR has wavelength dependence. In this case, the peak intensity in the reflection spectrum increases in a predetermined wavelength range. Therefore, by using a wavelength in a wavelength range having a large peak intensity in the reflection spectrum as the oscillation wavelength, laser oscillation at a wavelength other than the desired wavelength can be suppressed.

  In this embodiment, the semiconductor laser 10 corresponds to an optical element, the controller 50 corresponds to a control unit, the voltage detection unit 17 corresponds to a detection unit, and the semiconductor laser 10, the voltage detection unit 17 and the controller 50 include It corresponds to an optical device, the SG-DFB region 12 corresponds to an active region, and the SG-DBR region 11 corresponds to an optical waveguide portion.

  In the second embodiment, a semiconductor laser including the CSG-DBR will be described. FIG. 5 is a schematic diagram showing the overall configuration of a semiconductor laser 10a according to a second embodiment of the present invention and a laser apparatus 100a including the same. As shown in FIG. 5, the semiconductor laser 10 a includes a CSG-DBR region 11 a instead of the SG-DBR region 11. In this embodiment, it is assumed that the CSG-DBR region 11a has three sets of segments each consisting of a grating and a space. Therefore, the CSG-DBR region 11a is provided with three heaters 14a, 14b, and 14c corresponding to each segment. In addition, voltage detectors 17a, 17b, and 17c are provided corresponding to the heaters.

  In this embodiment, the amount of heat generated by each heater can be kept constant by performing feedback control so that the power supplied to each heater is kept constant based on the detection result of each voltage detector. . Thereby, even if the heater is deteriorated, the semiconductor laser 10a realizes a desired oscillation wavelength.

  In the CSG-DBR region, the number of gratings and the number of heaters are not particularly limited.

  The present invention can also be applied to optical elements other than semiconductor lasers. For example, the present invention can be applied to a Mach-Zehnder type optical switch. This optical switch is a switch used in an exchange system such as an optical cross connect.

  FIG. 6 is a schematic diagram showing the overall configuration of an optical switch 200 according to the third embodiment of the present invention. As shown in FIG. 6, the optical switch 200 is made of a material having a thermo-optic effect, such as a quartz material, and has a Mach-Zehnder interference structure including a first waveguide 201 and a second waveguide 202. The optical switch 200 is disposed on the temperature control device 210. Thereby, the temperature of each part of the optical switch 200 is controlled by the temperature control device 210.

  The optical switch 200 is provided with a heater 203. The heater 203 heats the second waveguide 202. Thereby, the phase difference between the light propagating through the first waveguide 201 and the light propagating through the second waveguide is changed, and the bar state and the cross state of the signal light in the first waveguide 201 and the second waveguide 202 are changed. Selected. Further, a voltage detection unit 204 is connected to the heater 203. The voltage detection unit 204 detects the voltage applied to the heater 203 and gives the detection result to the controller 220.

  In the present embodiment, the controller 220 controls the temperature control device 210 so that the temperature of the optical switch 200 is maintained at a predetermined temperature. The controller 220 performs feedback control based on the detection result of the voltage detection unit 204 so that the power supplied to the heater 203 is kept constant. In this case, even if the heater 203 deteriorates, the heat generation amount of the heater 203 is kept constant. Thereby, the phase difference between the light propagating through the first waveguide 201 and the light propagating through the second waveguide is kept constant. As a result, the switching reliability of the optical switch 200 is increased.

  In this embodiment, the optical switch 200 corresponds to an optical element, the controller 220 corresponds to a control unit, the voltage detection unit 204 corresponds to a detection unit, and the optical switch 200, the voltage detection unit 204, and the controller 220 include It corresponds to an optical device.

  The present invention can also be applied to an optical waveguide whose phase can be adjusted by a heater. FIG. 7 is a plan view showing a main part of an optical waveguide 300 according to the fourth embodiment of the present invention. As shown in FIG. 7, the optical waveguide 300 according to the present embodiment is an embedded waveguide, and a heater 302 is provided on the optical waveguide core 301. Since the optical waveguide core 301 according to the present embodiment simply propagates light, the waveguide core 301 is not provided with an optical structure such as a diffraction grating. The optical waveguide 300 is disposed on a temperature control device (not shown). The overall temperature of the optical waveguide 300 is controlled by this temperature control device.

  The optical waveguide core 301 is made of a quartz material or a material having a thermo-optic effect such as a semiconductor material such as GaInAsP or AlGaInAs. Furthermore, a voltage detection unit 303 is connected to the heater 302. The voltage detection unit 303 detects the voltage applied to the heater 302 and gives the detection result to the controller 304. The controller 304 controls the amount of power input to the heater 302 based on the detection result of the voltage detection unit 303.

  The optical length of the optical waveguide core 301 may deviate from the design value due to manufacturing variations. Such variation causes the phase of the optical signal passing through the optical waveguide core 301 to differ from the design value. This is a big problem for an optical device using the phase of an optical signal. In the present embodiment, a heater 302 for adjusting the phase of the laser light passing through the optical waveguide core 301 is provided. In order to absorb the manufacturing variation, the optical length of the optical waveguide core 301 can be finely adjusted by adjusting the temperature of the optical waveguide core 301 by the heat generated by the heater 302. In this case, by keeping the power supplied to the heater 302 constant, even if the heater 302 is deteriorated, the amount of heat generated by the heater 302 is kept constant. As a result, highly accurate control becomes possible.

  The optical waveguide 300 according to the present embodiment can also be applied to a Mach-Zehnder optical modulator. In this case, a difference in optical length between the two waveguides can be adjusted using a heater.

  In each of the above embodiments, the voltage applied to the heater is detected using a voltmeter, but the present invention is not limited to this. For example, the electric power may be controlled by detecting the current supplied to the heater using an ammeter and controlling the voltage applied to the heater. Further, the electric power supplied to the heater may be detected by a wattmeter, and the electric power may be controlled by controlling the current supplied to the heater and / or the voltage applied to the heater.

1 is a schematic diagram showing an overall configuration of a semiconductor laser according to a first embodiment of the present invention and a laser apparatus including the same. FIG. It is a figure which shows the example of a look-up table. It is a figure which shows the flowchart which shows an example of the control method of a laser apparatus. It is a figure which shows the detail of a voltage detection part. It is a schematic diagram which shows the whole structure of the semiconductor laser which concerns on 2nd Example of this invention, and a laser apparatus provided with the same. It is a schematic diagram which shows the whole structure of the optical switch which concerns on 3rd Example of this invention. It is a figure which shows the principal part top view of the optical waveguide which concerns on 4th Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor laser 11 SG-DBR area | region 12 SG-DFB area | region 13 SOA area | region 14 Heater 15, 16 Electrode 17 Voltage detection part 18 Voltmeter 20 Temperature control apparatus 30 Wavelength detection part 40 Output detection part 50 Controller 100 Laser apparatus 200 Optical switch 300 Optical waveguide

Claims (18)

An optical element having an optical waveguide whose refractive index is controlled by a heater, and an optical element whose temperature is controlled by a temperature control device;
A detector for measuring a current flowing through the heater and / or a voltage applied to the heater;
An optical device comprising: a control unit that keeps the electric power supplied to the heater constant based on a measurement result of the detection unit.   The optical device according to claim 1, wherein the detection unit measures a voltage across the heater.   The control unit controls the amount of current supplied to the heater, and is supplied to the heater based on the product of the measurement result of the voltage across the heater and the amount of current supplied to the heater. The optical device according to claim 2, wherein the power is determined. A terminal for supplying a current to the heater;
A terminal for grounding the heater;
The optical device according to claim 2, further comprising: a terminal connected to the heater separately from the terminal, and a terminal for measuring a voltage applied to the heater by the voltage detection unit.   The optical device according to claim 1, wherein the optical element is a wavelength tunable semiconductor laser.   2. The optical element according to claim 1, further comprising: an active region including a diffraction grating; and an optical waveguide portion that is optically coupled to the active region and includes a diffraction grating, and an equivalent refractive index is changed by the heater. Optical device.   The diffraction grating in the active region and the optical waveguide portion includes a first region having a diffraction grating, and a second region connected to the first region and serving as a space portion. Item 7. The optical device according to Item 6.   The optical element includes: an active region; and a pair of optical waveguide portions provided with optical coupling on both sides of the active region, at least one of which is provided with the heater and the equivalent refractive index is changed. The optical device according to claim 1.   2. The optical device according to claim 1, wherein the optical element is a Mach-Zehnder optical switch in which at least one of the pair of optical waveguides is an optical waveguide whose refractive index is controlled by the heater.   The optical device according to claim 1, wherein a diffraction grating is not provided in a region where the heater is provided in the optical waveguide. Controlling the temperature of the optical semiconductor element comprising an optical waveguide whose refractive index is controlled by a heater by a temperature control device;
A method for controlling an optical device, wherein the power is controlled based on a current flowing through the heater and / or a voltage applied to the heater so that the power supplied to the heater is kept constant.   12. The method of controlling an optical device according to claim 11, wherein the power is controlled by controlling a current supplied to the heater based on a voltage applied to the heater.   12. The method of controlling an optical device according to claim 11, wherein the optical element is a wavelength tunable semiconductor laser.   12. The optical element according to claim 11, comprising: an active region including a diffraction grating; and an optical waveguide portion that is optically coupled to the active region and includes a diffraction grating, and an equivalent refractive index is changed by the heater. Control method of optical device.   The diffraction grating in the active region and the optical waveguide portion includes a first region having a diffraction grating, and a second region connected to the first region and serving as a space portion. Item 15. A method for controlling an optical device according to Item 14.   The optical element includes: an active region; and a pair of optical waveguide portions provided with optical coupling on both sides of the active region, at least one of which is provided with the heater and the equivalent refractive index is changed. The method of controlling an optical device according to claim 11, wherein:   12. The optical device control method according to claim 11, wherein the optical element is a Mach-Zehnder optical switch in which at least one of the pair of optical waveguides is an optical waveguide whose refractive index is controlled by the heater.   12. The optical device according to claim 11, wherein an optical length of the optical waveguide different from a design is adjusted to a design optical length by controlling a refractive index of the optical waveguide by the heater. Control method.

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