JP2019140304A - Tunable laser device, and wavelength control method of tunable laser device - Google Patents

Abstract

To control the wavelength of laser light precisely to a target wavelength.SOLUTION: A control arrangement 3 constituting a tunable laser device 1 includes a temperature estimation part 311 for estimating the filter temperature of first and second filters, a monitor value calculation part 312 for calculating first and second monitor values, a target value correction part 314 for creating first and second correction control target values by correcting the first and second control target values, corresponding to the target wavelength of laser light and becoming the targets of the first and second monitor values, on the basis of the filter temperature, a target value selection part 315 for selecting any one of the first and second correction control target values, and an operation control section 316 for controlling the wavelength of the laser light outputted from a tunable light source, on the basis of a correction control target value selected by the target value selection part 315, and the monitor value having the correction control target value, out of the first and second monitor values, as the target value.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a wavelength tunable laser device and a wavelength control method for the wavelength tunable laser device.

2. Description of the Related Art Conventionally, in a wavelength tunable laser apparatus, a technique for controlling the wavelength of laser light to be output using an optical filter having periodic transmission characteristics with respect to the wavelength of incident light is known (for example, Patent Document 1) reference).
The wavelength tunable laser device described in Patent Document 1 includes a wavelength tunable light source unit that varies the wavelength of laser light to be output, a first light receiving element that acquires the intensity of laser light output from the wavelength tunable light source unit, An optical filter such as an etalon, a second light receiving element that acquires the intensity of laser light that has passed through the optical filter, and a control device (arithmetic circuit) that controls the operation of the wavelength variable light source unit.
Here, the control device calculates a monitor value for controlling the wavelength of the laser light based on the intensity of the laser light acquired by the first and second light receiving elements. In addition, the control device sets a control target value that is a target of the monitor value corresponding to the target wavelength of the laser light, using transmission characteristics at a predetermined temperature (hereinafter referred to as a reference temperature) in the optical filter. . Then, the control device controls the operation of the variable wavelength light source unit so that the monitor value matches the control target value.

JP2015-60961A

By the way, the transmission characteristics of the optical filter are such that when the temperature of the optical filter deviates from the reference temperature, the whole is shifted on the wavelength axis. That is, when the control target value corresponding to the target wavelength of the laser beam is set using the transmission characteristics at the reference temperature even though the temperature of the optical filter is deviated from the reference temperature, Since the transmission characteristic is shifted from the transmission characteristic at the reference temperature, the control target value is not a value corresponding to the target wavelength of the laser beam. For this reason, if the operation of the wavelength tunable light source unit is controlled so that the monitor value matches the control target value, the wavelength of the laser light is controlled to a wavelength shifted from the target wavelength.
Therefore, in the wavelength tunable laser device described in Patent Document 1, the temperature of the optical filter is controlled to be constant by the temperature control device. However, even if the temperature of the optical filter is controlled to be constant, the temperature variation inside the wavelength tunable laser device and the external heat inflow due to the environment such as the temperature outside the wavelength tunable laser device may occur unintentionally. In addition, the temperature of the optical filter may deviate from the reference temperature. That is, there is a problem that it is difficult to accurately control the wavelength of the laser light to the target wavelength.

  The present invention has been made in view of the above, and an object of the present invention is to provide a wavelength tunable laser device capable of accurately controlling the wavelength of laser light to a target wavelength, and a wavelength control method for the wavelength tunable laser device. And

  In order to solve the above-described problems and achieve the object, a wavelength tunable laser device according to the present invention includes a wavelength tunable light source unit that varies the wavelength of output laser light, and a laser output from the wavelength tunable light source unit. A first light receiving element for acquiring the intensity of light, a first optical filter having a first transmission characteristic whose characteristic periodically changes with respect to a wavelength of incident light, and the first optical filter that transmits the light. A second light receiving element for obtaining the intensity of the laser light, a second optical filter having a second transmission characteristic whose characteristics periodically change with respect to the wavelength of the incident light, and the second optical filter. A third light receiving element that acquires the intensity of the laser light that has passed through the light source, and a control device that controls the operation of the wavelength tunable light source unit. The control device includes the first optical filter and the second light. Estimate the filter temperature of the filter And a first monitor value based on the intensity of the laser beam acquired by the first light receiving element and the second light receiving element, and the first light receiving element and the third light receiving element A monitor value calculation unit that calculates a second monitor value based on the acquired intensity of the laser beam, and a first value that corresponds to the target wavelength of the laser beam and that is the target of the first monitor value based on the filter temperature. The first control target value is corrected to generate a first corrected control target value, and the second control target value corresponding to the target wavelength and serving as the target of the second monitor value is corrected to a second value. A target value correction unit that generates a correction control target value of the first correction control target value, a target value selection unit that selects one of the first correction control target value and the second correction control target value; Correction selected by the target value selection unit The wavelength of the laser light output from the wavelength tunable light source unit based on a target value and a monitor value having the correction control target value as a target value among the first monitor value and the second monitor value And an operation control unit for controlling the wavelength to the target wavelength.

  In the wavelength tunable laser device according to the present invention, in the above invention, the control device further includes a storage unit that stores target value correction information provided for each of a plurality of temperatures, and the target value correction information includes a plurality of target value correction information. And the target value correction unit refers to target value correction information corresponding to the filter temperature among the plurality of target value correction information, and the target value The first control target value and the second control target value are corrected using a correction value associated with the target wavelength among the plurality of correction values in the correction information.

  In the wavelength tunable laser device according to the present invention, in the above invention, the target value correction unit generates a correction value by interpolation from a plurality of correction values associated with the target wavelengths in the plurality of target value correction information. The correction value thus generated is used to correct the first control target value and the second control target value.

  In the wavelength tunable laser device according to the present invention, in the above invention, the control device includes temperature characteristic information indicating temperature characteristics in the first optical filter and the second optical filter, and the first transmission characteristic. And a storage unit for storing slope information indicating the second transmission characteristic, the temperature characteristic information is information indicating a wavelength shift amount per unit temperature, and the slope information is the first slope information. The information indicating the ratio of the fluctuation amount of the first monitor value and the second monitor value to the fluctuation amount of the wavelength of light incident on the optical filter and the second optical filter, the target value correction unit, A correction value is generated based on the temperature difference between the filter temperature and the reference temperature, the temperature characteristic information, and the slope information, and the first control target value and the first value are generated using the generated correction value. And correcting the control target value of.

  In the wavelength tunable laser device according to the present invention, in the above invention, the control device includes a first reference value information indicating the first transmission characteristic and a second reference value indicating the second transmission characteristic. The first reference value information is obtained by changing the wavelength of light incident on the first optical filter by one period in the first transmission characteristic. It is information indicating a first average value of the first monitor values, and the second reference value information varies the wavelength of light incident on the second optical filter by one period in the second transmission characteristic. Information indicating a second average value of the second monitor value at the time when the target value is selected, and the target value selection unit includes a difference between the first correction control target value and the first average value and the first average value. The difference between the correction control target value 2 and the difference between the second average values is small. And selects the correction control target value.

  In the wavelength tunable laser device according to the present invention, in the above invention, the storage unit further stores variation range information indicating a variation range, and the target value selection unit focuses on the correction control target value selected immediately before. When the correction control target value newly generated by the target value correction unit and corresponding to the correction control target value selected immediately before is included in the fluctuation range, the newly generated Even when a correction control target value different from the correction control target value is closer to the average value, the newly generated correction control target value is selected.

  In the wavelength tunable laser device according to the present invention, in the above invention, the control device corresponds to the first wavelength when laser light having the first wavelength is input to the first optical filter. A storage unit that stores expected monitor value information indicating an expected monitor value expected as the first monitor value, wherein the temperature estimation unit applies the laser light of the first wavelength to the first optical filter; The filter temperature is estimated based on a difference between the first monitor value and the expected monitor value when input.

  The wavelength tunable laser device according to the present invention may further include a temperature sensor that detects an ambient temperature of the wavelength tunable laser device according to the above invention, and the temperature estimation unit may calculate the filter temperature based on the ambient temperature. It is characterized by estimating.

  Further, the wavelength tunable laser device according to the present invention includes a wavelength tunable light source unit that makes the wavelength of the laser beam to be output variable, and a first light receiving element that acquires the intensity of the laser beam output from the wavelength tunable light source unit. A first optical filter having a first transmission characteristic whose characteristics periodically change with respect to the wavelength of the incident light, and a second light receiving unit for acquiring the intensity of the laser light transmitted through the first optical filter. An element, a second optical filter having a second transmission characteristic whose characteristics periodically change with respect to the wavelength of incident light, and a third for acquiring the intensity of the laser light transmitted through the second optical filter. The light receiving element and a control device that controls the operation of the wavelength tunable light source unit, and the control device estimates a filter temperature of the first optical filter and the second optical filter, and The first light receiving element and the second light receiving element A first monitor value is calculated based on the intensity of the laser light acquired by the light receiving element, and a second monitor value is calculated based on the intensity of the laser light acquired by the first light receiving element and the third light receiving element. A monitor value calculation unit for calculating the first monitor target value corresponding to the target wavelength of the laser beam and the target of the first monitor value, and the second monitor value corresponding to the target wavelength. A target value selection unit that selects any one of the target control target values and a control target value selected by the target value selection unit based on the filter temperature. A target value correction unit that generates a correction control target value, the correction control target value, and a monitor value that uses the correction control target value as a target value among the first monitor value and the second monitor value. Based on the tunable light source The wavelength of the laser beam output from, characterized in that it comprises an operation control unit for controlling the target wavelength.

  A wavelength control method for a wavelength tunable laser device according to the present invention includes a wavelength tunable light source unit that varies a wavelength of laser light to be output, and a first light receiving unit that acquires the intensity of the laser light output from the wavelength tunable light source unit. An element, a first optical filter having a first transmission characteristic whose characteristics periodically change with respect to the wavelength of incident light, and a second for acquiring the intensity of laser light transmitted through the first optical filter. Light receiving elements, a second optical filter having a second transmission characteristic whose characteristics periodically change with respect to the wavelength of incident light, and the intensity of the laser light transmitted through the second optical filter. A wavelength control method for a wavelength tunable laser device comprising a third light receiving element, the temperature estimating step for estimating filter temperatures of the first optical filter and the second optical filter, and the first light receiving Element and second light receiving element The first monitor value is calculated based on the intensity of the laser beam acquired by the child, and the second monitor value is calculated based on the intensity of the laser beam acquired by the first light receiving element and the third light receiving element. Based on the monitor value calculation step to be calculated and the filter temperature, the first control target value corresponding to the target wavelength of the laser beam and correcting the first control target value that is the target of the first monitor value is corrected. A target value correcting step for generating a value and correcting a second control target value corresponding to the target wavelength and serving as a target of the second monitor value to generate a second corrected control target value; A target value selection step for selecting one of the first correction control target value and the second correction control target value; a correction control target value selected in the target value selection step; The first Operation control for controlling the wavelength of the laser light output from the wavelength tunable light source unit to the target wavelength based on the monitor value and the monitor value having the correction control target value as the target value among the monitor value and the second monitor value And a step.

  A wavelength control method for a wavelength tunable laser device according to the present invention includes a wavelength tunable light source unit that varies a wavelength of laser light to be output, and a first light receiving unit that acquires the intensity of the laser light output from the wavelength tunable light source unit. An element, a first optical filter having a first transmission characteristic whose characteristics periodically change with respect to the wavelength of incident light, and a second for acquiring the intensity of laser light transmitted through the first optical filter. Light receiving elements, a second optical filter having a second transmission characteristic whose characteristics periodically change with respect to the wavelength of incident light, and the intensity of the laser light transmitted through the second optical filter. A wavelength control method for a wavelength tunable laser device comprising a third light receiving element, the temperature estimating step for estimating filter temperatures of the first optical filter and the second optical filter, and the first light receiving Element and second light receiving element The first monitor value is calculated based on the intensity of the laser beam acquired by the child, and the second monitor value is calculated based on the intensity of the laser beam acquired by the first light receiving element and the third light receiving element. A monitor value calculating step to calculate; a first control target value corresponding to the target wavelength of the laser beam and serving as a target of the first monitor value; and a target of the second monitor value corresponding to the target wavelength. A target value selection step for selecting any one of the second control target values to be corrected, and the control target value selected in the target value selection step is corrected based on the filter temperature. Based on a target value correcting step for generating a control target value, the corrected control target value, and a monitor value that uses the corrected control target value as a target value among the first monitor value and the second monitor value. , The wavelength of the laser beam output from the serial wavelength tunable light source unit characterized in that it comprises an operation control unit for controlling the target wavelength.

  According to the wavelength tunable laser device and the wavelength control method of the wavelength tunable laser device according to the present invention, there is an effect that the wavelength of the laser light can be controlled to the target wavelength with high accuracy.

FIG. 1 is a diagram illustrating a configuration of a wavelength tunable laser device according to the first embodiment. FIG. 2 is a diagram illustrating a configuration of the wavelength tunable light source unit. FIG. 3 is a block diagram illustrating a configuration of the control device. FIG. 4 is a diagram illustrating the wavelength power information stored in the storage unit. FIG. 5 is a diagram illustrating the transmission characteristic information stored in the storage unit. FIG. 6 is a diagram illustrating the transmission characteristic information stored in the storage unit. FIG. 7 is a diagram illustrating a plurality of target value correction information stored in the storage unit. FIG. 8 is a flowchart showing a wavelength control method by the control device. FIG. 9 is a diagram for explaining a wavelength control method. FIG. 10 is a block diagram illustrating a configuration of the control device according to the second embodiment. FIG. 11 is a flowchart illustrating a wavelength control method by the control device. FIG. 12 is a diagram illustrating the slope information stored in the storage unit. FIG. 13 is a block diagram illustrating a configuration of a control device according to the third embodiment. FIG. 14 is a flowchart illustrating a wavelength control method by the control device. FIG. 15 is a block diagram showing a configuration of a control device according to the fourth embodiment. FIG. 16 is a flowchart illustrating a wavelength control method by the control device. FIG. 17 is a diagram for explaining a wavelength control method. FIG. 18 is a diagram for explaining a wavelength control method. FIG. 19 is a block diagram illustrating a configuration of a control device according to the fifth embodiment. FIG. 20 is a flowchart illustrating a wavelength adjustment control method by the control device.

  DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter, embodiments) will be described with reference to the drawings. The present invention is not limited to the embodiments described below. Furthermore, the same code | symbol is attached | subjected to the same part in description of drawing. Further, the drawings are schematic, and the dimensional relationship of each element, the ratio of each element, and the like may be different from the actual ones. Furthermore, there are cases in which parts having different dimensional relationships and ratios are included between the drawings. In addition, xyz coordinate axes are appropriately shown in the drawing, and directions will be described.

(Embodiment 1)
[Schematic configuration of wavelength tunable laser device]
FIG. 1 is a diagram showing a configuration of a wavelength tunable laser device 1 according to the first embodiment.
The wavelength tunable laser device 1 includes a modularized wavelength tunable laser module 2, a control device 3 that controls the operation of the wavelength tunable laser module 2, and a temperature sensor 8.
In FIG. 1, the wavelength tunable laser module 2 and the control device 3 are configured separately, but the members 2 and 3 may be integrated into a module.

[Configuration of tunable laser module]
The wavelength tunable laser module 2 changes the wavelength of the laser beam to be output to one of a plurality of wavelengths under the control of the control device 3, and outputs the laser beam having the one wavelength. The wavelength tunable laser module 2 includes a wavelength tunable light source section 4, a semiconductor optical amplifier (SOA) 5, a planar lightwave circuit (PLC) 6, a light detection section 7, and a temperature controller. 9.

FIG. 2 is a diagram illustrating a configuration of the wavelength tunable light source unit 4.
The wavelength tunable light source unit 4 is a wavelength tunable laser using, for example, a vernier effect, and outputs laser light L1 under the control of the control device 3. The wavelength tunable light source unit 4 includes a light source unit 41 that changes the wavelength of the laser beam L1 to be output, and three micro heaters 421 to 423 that generate heat according to the power supplied from the control device 3. A wavelength variable unit 42 that changes the wavelength of the laser light L <b> 1 output from the light source unit 41 by locally heating 41 is provided.

  The light source unit 41 includes first and second waveguide portions 43 and 44 formed on a common base B1. Here, the base B1 is made of, for example, n-type InP. On the back surface of the base B1, for example, an n-side electrode 45 made of AuGeNi and in ohmic contact with the base B1 is formed.

The first waveguide portion 43 has a buried waveguide structure. The first waveguide section 43 includes a waveguide section 431, a semiconductor stacked section 432, and a p-side electrode 433.
The waveguide portion 431 is formed in the semiconductor stacked portion 432 so as to extend in the z direction.
In the first waveguide section 43, a gain section 431a and a DBR (Distributed Bragg Reflector) type diffraction grating layer 431b are arranged.
Here, the gain section 431a is an active layer having a multiple quantum well structure made of InGaAsP and an optical confinement layer. The diffraction grating layer 431b is composed of a sampling diffraction grating made of InGaAsP and InP.

The semiconductor laminated portion 432 is configured by laminating InP-based semiconductor layers, and has a function of a clad portion with respect to the waveguide portion 431.
The p-side electrode 433 is disposed along the gain portion 431a on the semiconductor stacked portion 432. Note that a SiN protective film (not shown) is formed on the semiconductor stacked portion 432. The p-side electrode 433 is in contact with the semiconductor stacked portion 432 through an opening (not shown) formed in the SiN protective film.
Here, the microheater 421 is arranged along the diffraction grating layer 431 b on the SiN protective film of the semiconductor stacked portion 432. The microheater 421 generates heat according to the power supplied from the control device 3 and heats the diffraction grating layer 431b. Further, the power of the control device 3 supplied to the micro heater 421 changes the temperature of the diffraction grating layer 431b and changes its refractive index.

The second waveguide portion 44 includes a bifurcated portion 441, two arm portions 442 and 443, and a ring-shaped waveguide 444.
The two-branch portion 441 is formed of a 1 × 2 type branching waveguide including a 1 × 2 type multimode interference (MMI) waveguide 441a, and the two-port side is connected to each of the two arm portions 442 and 443. In addition, one port side is connected to the first waveguide portion 43 side. That is, one end of the two arm portions 442 and 443 is integrated by the bifurcated portion 441 and is optically coupled to the diffraction grating layer 431b.

Each of the arm portions 442 and 443 extends in the z direction and is disposed so as to sandwich the ring-shaped waveguide 444. These arm portions 442 and 443 are optically coupled to the ring-shaped waveguide 444 with the same coupling coefficient κ as the ring-shaped waveguide 444. The value of κ is 0.2, for example. The arm portions 442 and 443 and the ring-shaped waveguide 444 constitute a ring resonator filter RF1. The ring resonator filter RF1 and the bifurcated portion 441 constitute a reflection mirror M1.
Here, the microheater 422 has a ring shape and is disposed on a SiN protective film (not shown) formed so as to cover the ring-shaped waveguide 444. The microheater 422 generates heat according to the power supplied from the control device 3 and heats the ring-shaped waveguide 444. Moreover, the temperature of the ring-shaped waveguide 444 is changed by controlling the electric power supplied to the micro heater 422 by the control device 3, and the refractive index thereof is changed.

The above-described bifurcated portion 441, arm portions 442 and 443, and ring-shaped waveguide 444 all have a high mesa waveguide structure in which an optical waveguide layer 44a made of InGaAsP is sandwiched between cladding layers made of InP. .
Here, the micro heater 423 is disposed on a part of the SiN protective film (not shown) of the arm portion 443. A region below the microheater 423 in the arm unit 443 functions as a phase adjustment unit 445 that changes the phase of light. The microheater 423 generates heat according to the power supplied from the control device 3 and heats the phase adjustment unit 445. In addition, the control device 3 controls the power supplied to the microheater 423, so that the temperature of the phase adjusting unit 445 changes and the refractive index thereof changes.

  The first and second waveguide portions 43 and 44 described above constitute an optical resonator C1 including a diffraction grating layer 431b and a reflection mirror M1 that are optically connected to each other. The gain unit 431a and the phase adjustment unit 445 are disposed in the optical resonator C1.

The diffraction grating layer 431b generates a first comb-like reflection spectrum having substantially periodic reflection characteristics at substantially predetermined wavelength intervals. On the other hand, the ring resonator filter RF1 generates a second comb-like reflection spectrum having reflection characteristics that are substantially periodic at substantially predetermined wavelength intervals.
Here, the second comb-like reflection spectrum has a peak with a full width at half maximum narrower than the full width at half maximum of the peak of the first comb-like reflection spectrum, and a wavelength interval different from the wavelength interval of the first comb-like reflection spectrum. And has a substantially periodic reflection characteristic. However, in consideration of the wavelength dispersion of the refractive index, it should be noted that the spectral components are not strictly equal wavelength intervals.

  Illustrating the characteristics of each comb-like reflection spectrum, the wavelength interval (free spectral region: FSR) between the peaks of the first comb-like reflection spectrum is 373 GHz in terms of the frequency of light. The full width at half maximum of each peak is 43 GHz in terms of the frequency of light. On the other hand, the wavelength interval (FSR) between peaks of the second comb-like reflection spectrum is 400 GHz in terms of the frequency of light. The full width at half maximum of each peak is 25 GHz in terms of light frequency. That is, the full width at half maximum (25 GHz) of each peak of the second comb-like reflection spectrum is narrower than the full width at half maximum (43 GHz) of each peak of the first comb-like reflection spectrum.

  The tunable light source unit 4 is configured to be able to superimpose one of the peaks of the first comb-like reflection spectrum and one of the peaks of the second comb-like reflection spectrum on the wavelength axis in order to realize laser oscillation. ing. In such superposition, at least one of the microheaters 421 and 422 is used, the diffraction grating layer 431b is heated by the microheater 421, and the refractive index thereof is changed by the thermo-optic effect to change the first comb-like reflection spectrum. The second comb-like reflection spectrum is entirely changed on the wavelength axis by changing the refractive index by heating the ring-shaped waveguide 444 by the microheater 422. It is realizable by performing at least any one of moving to and changing.

  On the other hand, in the wavelength tunable light source unit 4, there is a resonator mode by the optical resonator C1. In the wavelength tunable light source unit 4, the resonator length of the optical resonator C1 is set so that the resonator mode interval (longitudinal mode interval) is 25 GHz or less. In the case of this setting, the resonator length of the optical resonator C1 is 1800 μm or more, and a narrow linewidth of the oscillating laser light can be expected. Note that the wavelength of the resonator mode of the optical resonator C1 is moved entirely on the wavelength axis by heating the phase adjusting unit 445 using the microheater 423 and changing the refractive index thereof. Can be finely adjusted. That is, the phase adjustment unit 445 is a part for actively controlling the optical path length of the optical resonator C1.

When the control device 3 injects current from the n-side electrode 45 and the p-side electrode 433 to the gain unit 431a and causes the gain unit 431a to emit light, the wavelength tunable light source unit 4 emits a spectral component of the first comb-like reflection spectrum. The laser is oscillated at a wavelength at which the peak, the peak of the spectral component of the second comb-like reflection spectrum, and one of the resonator modes of the optical resonator C1 coincide, for example, 1550 nm, and the laser beam L1 is output. .
In addition, the wavelength tunable light source unit 4 can change the wavelength of the laser light L1 using the vernier effect. For example, when the diffraction grating layer 431b is heated by the micro heater 421, the refractive index of the diffraction grating layer 431b increases due to the thermo-optic effect, and the first comb-like reflection spectrum of the diffraction grating layer 431b is shifted to the long wave side as a whole. To do. As a result, the peak of the first comb-like reflection spectrum near 1550 nm is unoverlapped with the peak of the second comb-like reflection spectrum of the ring resonator filter RF1, and the second comb-like reflection existing on the long wave side is removed. It overlaps with another peak of the spectrum (for example, around 1556 nm). Further, by tuning the phase adjustment unit 445 to finely adjust the resonator mode and superimposing one of the resonator modes on the two comb-like reflection spectra, laser oscillation at around 1556 nm can be realized. That is, in the wavelength tunable light source unit 4, the first and second comb-like reflection spectra are respectively tuned by the microheater 421 for the diffraction grating layer 431b and the microheater 422 for the ring resonator filter RF1, thereby coarsely adjusting and adjusting the phase. Tuning the resonator length by the micro heater 423 for the unit 445 realizes a wavelength tunable operation for fine adjustment.

  Although not specifically shown, the semiconductor optical amplifier 5 has a buried waveguide structure including an active core layer made of the same material and structure as that of the first waveguide section 43. However, the diffraction grating layer 431b is not provided. The semiconductor optical amplifier 5 is optically coupled to the wavelength tunable light source unit 4 by a spatial coupling optical system (not shown). The laser light L1 output from the wavelength variable light source unit 4 is input to the semiconductor optical amplifier 5. The semiconductor optical amplifier 5 amplifies the laser light L1 and outputs it as laser light L2. The semiconductor optical amplifier 5 may be configured monolithically with the wavelength variable light source unit 4 on the base B1.

  The planar lightwave circuit 6 is optically coupled to the arm portion 442 by a spatial coupling optical system (not shown). A part of the laser light L 3 generated by laser oscillation in the wavelength tunable light source unit 4 is input to the planar lightwave circuit 6 via the arm unit 442 as in the case of the laser light L 1. The laser beam L3 has the same wavelength as that of the laser beam L1. As shown in FIG. 1, the planar lightwave circuit 6 includes an optical branch 61, an optical waveguide 62, an optical waveguide 63 having a ring resonator type optical filter 63a, and an optical waveguide having a ring resonator type optical filter 64a. 64.

The light branching unit 61 branches the input laser beam L3 into three laser beams L4 to L6.
The optical waveguide 62 guides the laser light L4 to a PD (Photo Diode) 71 (to be described later) in the light detection unit 7. The optical waveguide 63 guides the laser beam L5 to a PD 72 (to be described later) in the light detection unit 7. Further, the optical waveguide 64 guides the laser light L6 to a PD 73 (to be described later) in the light detection unit 7.
Here, the ring resonator type optical filters 63a and 64a each have a periodic transmission characteristic with respect to the wavelength of the incident light, and selectively select the laser beams L5 and L6 with a transmittance according to the transmission characteristic. Transparent to. The laser beams L5 and L6 that have passed through the ring resonator type optical filters 63a and 64a are input to the PDs 72 and 73, respectively. That is, the ring resonator type optical filters 63a and 64a correspond to the first and second optical filters according to the present invention. Hereinafter, for convenience of explanation, the ring resonator type optical filter 63a is described as a first optical filter 63a, and the ring resonator type optical filter 64a is described as a second optical filter 64a.
The first and second optical filters 63a and 64a have transmission characteristics whose phases are different from each other within a range of 1/3 to 1/5 of one cycle, for example. That is, the transmission characteristic of the first optical filter 63a (corresponding to the first transmission characteristic according to the present invention) and the transmission characteristic of the second optical filter 64a (corresponding to the second transmission characteristic of the present invention) are mutually different. Only the phase is different.

As shown in FIG. 1, the light detection unit 7 includes PDs 71 to 73.
The PD 71 receives the laser light L4 (same as the laser light L1 output from the wavelength variable light source unit 4), and outputs an electrical signal corresponding to the intensity of the laser light L4 to the control device 3. That is, the PD 71 corresponds to the first light receiving element according to the present invention.
The PD 72 receives the laser light L5 that has passed through the first optical filter 63a, and outputs an electrical signal corresponding to the intensity of the laser light L5 to the control device 3. That is, the PD 72 corresponds to the second light receiving element according to the present invention.
The PD 73 receives the laser light L6 that has passed through the second optical filter 64a, and outputs an electrical signal corresponding to the intensity of the laser light L6 to the control device 3. That is, the PD 73 corresponds to the third light receiving element according to the present invention.
The electrical signals output from the PDs 71 to 73 are used for wavelength lock control (control for setting the laser light L1 output from the wavelength variable light source unit 4 to the target wavelength) by the control device 3.

The temperature sensor 8 is composed of, for example, a thermistor and detects the temperature of the environment in which the wavelength tunable laser device 1 is disposed as the ambient temperature. The temperature of the wavelength variable light source unit 4 and the planar lightwave circuit 6 installed on the temperature controller 9 may be detected as the ambient temperature.
The temperature controller 9 is composed of, for example, a TEC (Thermo Electric Cooler) including a Peltier element. On this temperature controller 9, the wavelength variable light source unit 4, the semiconductor optical amplifier 5, the planar lightwave circuit 6, and the light detection unit 7 are mounted. And the temperature regulator 9 adjusts the temperature of the said members 4-7 according to the supplied electric power. In addition, when detecting the temperature of the wavelength variable light source unit 4 and the planar lightwave circuit 6 as the ambient temperature, the temperature sensor 8 may be mounted on the temperature controller 9. At this time, in the temperature controller 9, the installation surface 91 on which the respective members 4 to 7 are placed is arranged on the first region Ar 1 on which the wavelength variable light source unit 4 and the semiconductor optical amplifier 5 are placed, and the planar lightwave circuit 6. When the temperature sensor 8 is divided into two regions, the second region Ar2 where the light detection unit 7 is placed, the temperature sensor 8 may be placed in the second region Ar2. That is, the temperature sensor 8 may be disposed close to the planar lightwave circuit 6.

[Configuration of control device]
Next, the configuration of the control device 3 will be described.
FIG. 3 is a block diagram illustrating a configuration of the control device 3.
The control device 3 is connected to a host control device (not shown) having a user interface, for example, and controls the operation of the wavelength tunable laser module 2 in accordance with an instruction from the user via the host control device. .
In the following, the wavelength lock control by the control device 3 which is the main part of the present invention will be mainly described. Further, in FIG. 3, for convenience of explanation, only the configuration for performing wavelength lock control is illustrated as the configuration of the control device 3.
The control device 3 includes a control unit 31 and a storage unit 32.

The control unit 31 is configured using a CPU or the like. The control unit 31 includes a temperature estimation unit 311, a monitor value calculation unit 312, a target value calculation unit 313, a target value correction unit 314, a target value selection unit 315, and an operation control unit 316.
The temperature estimation unit 311 estimates the temperature of the planar lightwave circuit 6 (first and second optical filters 63a and 64a) (hereinafter referred to as filter temperature) based on the ambient temperature detected by the temperature sensor 8. . For example, the temperature estimation unit 311 includes the target wavelength acquired from the host control device (not shown), the ambient temperature detected by the temperature sensor 8, the thermal resistance information and the wavelength power information stored in the storage unit 32. Based on the above, the filter temperature is estimated.
Here, the thermal resistance information is information indicating the thermal resistance between the temperature sensor 8 and the planar lightwave circuit 6 in the wavelength tunable laser module 2.
FIG. 4 is a diagram illustrating the wavelength power information stored in the storage unit 32.
The wavelength power information includes a plurality of wavelengths λ1 to λn [nm] and a plurality of powers (initial powers) supplied to the microheaters 421 to 423 in order to control the wavelength of the laser light L1 to the wavelengths λ1 to λn [nm]. ) And associated information. In FIG. 4, for convenience of explanation, the total power supplied to the microheaters 421 to 423 is shown as each power P1 to Pn [W].

  The monitor value calculation unit 312 calculates the first and second monitor values for controlling the wavelength of the laser light L1 based on the output values of the electrical signals output from the PDs 71 to 73, respectively. Specifically, the monitor value calculation unit 312 calculates the ratio of the output value of the electrical signal output from the PD 72 to the output value of the electrical signal output from the PD 71 as a first monitor value (hereinafter referred to as a first PD ratio). ). The monitor value calculation unit 312 uses a ratio of the output value of the electrical signal output from the PD 73 to the output value of the electrical signal output from the PD 71 as a second monitor value (hereinafter referred to as a second PD ratio). calculate.

The target value calculation unit 313 performs the first control that is the target of the first PD ratio based on the target wavelength acquired from the higher-level control device (not shown) and the transmission characteristic information stored in the storage unit 32. A target value and a second control target value that is a target of the second PD ratio are calculated.
5 and 6 are diagrams showing the transmission characteristic information stored in the storage unit 32. FIG. In FIG. 6, the horizontal axis represents the wavelength and the vertical axis represents the PD ratio.
The transmission characteristic information includes information indicating the transmission characteristic of the first optical filter 63a at the reference temperature (for example, 35 ° C.) (hereinafter referred to as first transmission characteristic information) and the first characteristic at the reference temperature (for example, 35 ° C.). Information indicating the transmission characteristics of the second optical filter 64a (hereinafter referred to as second transmission characteristic information).

More specifically, the first transmission characteristic information is output from the PD 71 when the plurality of wavelengths λ1 to λn [nm] and the wavelength of the laser light L1 are set to the wavelengths λ1 to λn [nm], respectively. A plurality of control reference values Pd11 to Pd1n that are reference values of the first PD ratios, which are ratios of the output values of the electric signals output from the PD 72 to the output values of the electric signals, are associated with each other. Note that the first PD ratio is substantially proportional to the transmittance of the first optical filter 63a. Therefore, the first transmission characteristic information indicates the transmission characteristic (curve CL1 in FIG. 6) at the reference temperature (for example, 35 ° C.) in the first optical filter 63a.
On the other hand, the second transmission characteristic information includes the plurality of wavelengths λ1 to λn [nm] and the electrical signal output from the PD 71 when the wavelengths of the laser light L1 are set to the wavelengths λ1 to λn [nm], respectively. This is information in which a plurality of control reference values Pd21 to Pd2n that are reference values of each second PD ratio, which is a ratio of the output value of the electric signal output from the PD 73 to the output value, are associated with each other. Note that the second PD ratio is substantially proportional to the transmittance of the second optical filter 64a. Therefore, the second transmission characteristic information indicates the transmission characteristic (curve CL2 in FIG. 6) at the reference temperature (for example, 35 ° C.) in the second optical filter 64a.

  Then, the transmission characteristic (curve CL1) of the first optical filter 63a has a wavelength as shown by a curve CL1 ′ in FIG. 6 when the temperature of the first optical filter 63a deviates from a reference temperature (for example, 35 ° C.). The whole shifts to the short wave side or the long wave side on the axis. Similarly, when the temperature of the second optical filter 64a deviates from a reference temperature (for example, 35 ° C.), the transmission characteristic (curve CL2) of the second optical filter 64a is as shown by a curve CL2 ′ in FIG. The whole shifts to the short wave side or the long wave side on the wavelength axis. In addition, in FIG. 6, the state shifted to the long wave side is illustrated.

The target value correction unit 314 is a first value calculated by the target value calculation unit 313 based on the filter temperature estimated by the temperature estimation unit 311 and the plurality of target value correction information stored in the storage unit 32. The first control target value is generated by correcting the second control target value.
FIG. 7 is a diagram illustrating a plurality of target value correction information stored in the storage unit 32.
The plurality of target value correction information includes a plurality of first target value correction information for correcting the first control target value and a plurality of second target value correction information for correcting the second control target value. Including.

More specifically, the first target value correction information includes a plurality of wavelengths λ1 for each of a plurality of temperatures (three temperatures of “30 ° C.”, “35 ° C.”, and “40 ° C.” in the example of FIG. 7). ~ Λn [nm] and a plurality of correction values for correcting the first control target value (in the example of FIG. 7, “A1”, “0”, and “A2”) are information associated with each other. is there. In FIG. 7, only the first target value correction information related to the wavelength λ1 is illustrated for convenience of explanation.
On the other hand, the second target value correction information includes a plurality of wavelengths λ1 to λn for each of a plurality of temperatures (three temperatures of “30 ° C.”, “35 ° C.”, and “40 ° C.” in the example of FIG. 7). [nm] and correction values for correcting the second control target value (in the example of FIG. 7, “B1”, “0”, and “B2”) are information associated with each other. In FIG. 7, for convenience of explanation, only the second target value correction information related to the wavelength λ1 is illustrated.

The target value selection unit 315 is one of the first and second correction control target values generated by the target value correction unit 314 based on the reference value information stored in the storage unit 32. Select.
Here, the reference value information corresponds to the first and second reference value information according to the present invention, and is information indicating the transmission characteristics of the first and second optical filters 63a and 64a. Specifically, the reference value information is the electric signal output from the PD 71 when the wavelength of the light incident on the first optical filter 63a is changed by one period in the transmission characteristic of the first optical filter 63a. This is information indicating the average value AV (FIG. 6) of each first PD ratio, which is the ratio of the output value of the electrical signal output from the PD 72 to the output value. The transmission characteristics of the first and second optical filters 63a and 64a are only different in phase. For this reason, the wavelength of the light incident on the second optical filter 64a is output from the PD 73 for the output value of the electrical signal output from the PD 71 when the transmission characteristic of the second optical filter 64a is changed by one period. The average value of the second PD ratios, which is the ratio of the output values of the electrical signals, is the same value as the average value AV described above.

The operation control unit 316 includes a target wavelength acquired from a higher-level control device (not shown), wavelength power information stored in the storage unit 32, a correction control target value selected by the target value selection unit 315, a first Based on the PD ratio in which the correction control target value is a target value among the first and second PD ratios, a plurality of electric powers respectively supplied to the microheaters 421 to 423 are changed, and the wavelength of the laser light L1 is changed to the target wavelength. To control.
The storage unit 32 is a program executed by the control unit 31 and information necessary for processing of the control unit 31 (for example, thermal resistance information, wavelength power information, transmission characteristic information, a plurality of target value correction information, and a reference value) Information, etc.).

[Wavelength control method]
Next, the wavelength control method (wavelength lock control) by the control device 3 described above will be described.
FIG. 8 is a flowchart showing a wavelength control method by the control device 3.
First, the operation control unit 316 obtains a target wavelength input from a higher-level control device (not shown) via the user interface from the higher-level control device (step S1).
After step S1, the target value calculation unit 313 refers to the transmission characteristic information stored in the storage unit 32 and calculates the first and second control target values (step S2). Specifically, the target value calculation unit 313 reads the first transmission characteristic information stored in the storage unit 32. Then, the target value calculation unit 313 controls the control reference value (for example, the wavelength λ1) associated with the target wavelength (for example, the wavelength λ1) acquired in step S1 among the plurality of control reference values Pd11 to Pd1n in the first transmission characteristic information. For example, the control reference value Pd11) is calculated as the first control target value. The target value calculation unit 313 reads the second transmission characteristic information stored in the storage unit 32. Then, the target value calculation unit 313 controls the control reference value (for example, the wavelength λ1) associated with the target wavelength (for example, the wavelength λ1) acquired in step S1 among the plurality of control reference values Pd21 to Pd2n in the second transmission characteristic information. For example, the control reference value Pd21) is calculated as the second control target value.

After step S2, the operation control unit 316 refers to the wavelength power information stored in the storage unit 32, and converts each power (initial power) associated with the target wavelength acquired in step S1 to the microheaters 421 to 423. (Step S3).
After step S <b> 3, the monitor value calculation unit 312 outputs the first PD ratio, which is the ratio of the output value of the electrical signal output from the PD 72 to the output value of the electrical signal output from the PD 71, and the electrical signal output from the PD 71. The second PD ratio, which is the ratio of the output value of the electrical signal output from the PD 73 to the output value of, is calculated (step S4: monitor value calculation step).

After step S4, the control device 3 detects the ambient temperature using the temperature sensor 8 (step S5).
After step S5, the temperature estimation unit 311 refers to the wavelength power information stored in the storage unit 32, and among the powers P1 to Pn [W], the power associated with the target wavelength acquired in step S1. Is recognized as the total power currently supplied to the micro heaters 421 to 423. The temperature estimation unit 311 then calculates the filter temperature of the planar lightwave circuit 6 based on the recognized total power, the ambient temperature detected in step S5, and the thermal resistance based on the thermal resistance information stored in the storage unit 32. Is estimated (step S6: temperature estimation step).

After step S6, the target value correction unit 314 calculates the first value calculated in step S2 based on the filter temperature estimated in step S6 and the plurality of target value correction information stored in the storage unit 32. , The second control target value is corrected to generate first and second correction control target values (step S7: target value correction step). Specifically, the target value correction unit 314 includes the filter temperature estimated in step S6 among the plurality of first target value correction information stored in the storage unit 32 (for example, when the ambient temperature is 70 ° C.). First target value correction information corresponding to a filter temperature of 40 ° C. is read out. The target value correction unit 314 then corrects the correction value associated with the target wavelength (for example, the wavelength λ1) acquired in step S1 among the plurality of correction values in the first target value correction information corresponding to the filter temperature. (For example, the correction value A2) is added to the first control target value calculated in step S2 to generate the first correction control target value. Further, the target value correction unit 314 reads out second target value correction information corresponding to the filter temperature estimated in step S <b> 6 among the plurality of second target value correction information stored in the storage unit 32. Then, the target value correction unit 314 corrects the correction value associated with the target wavelength (for example, the wavelength λ1) acquired in step S1 among the plurality of correction values in the second target value correction information corresponding to the filter temperature. (For example, the correction value B2) is added to the second control target value calculated in step S2 to generate a second correction control target value.
Note that the target value correction unit 314 does not store target value correction information at the same temperature as the filter temperature estimated in step S6 in step S7 (for example, the filter temperature is shown in FIG. 7). The temperature between 30 ° C. and 35 ° C., or the temperature between 35 ° C. and 40 ° C.) by interpolation from a plurality of correction values associated with target wavelengths in a plurality of target value correction information. A correction value is generated, and the first and second control target values are corrected using the correction value.

After step S7, the target value selection unit 315 corrects the average value AV based on the reference value information stored in the storage unit 32 among the first and second correction control target values generated in step S7. A control target value is selected (step S8: target value selection step).
After step S8, the operation control unit 316 sets the correction control target value among the first and second PD ratios calculated in step S4 with respect to the correction control target value selected in step S8. Wavelength adjustment control for changing the power supplied to each of the micro heaters 421 to 423 is executed so that the PD ratio as the target value matches (step S9: operation control step). The “PD ratio with the correction control target value as a target value” means the first PD ratio when the first correction control target value is selected in step S8, and the process proceeds to step S8. When the second correction control target value is selected, it means the second PD ratio.
Further, in FIG. 8, for convenience of explanation, the flow for completing the wavelength lock control after step S9 is shown. However, actually, after step S9, the process returns to step S4, and the loop of steps S4 to S9 is repeated. The wavelength of the laser beam L1 is controlled to the target wavelength.

FIG. 9 is a diagram for explaining a wavelength control method. Specifically, FIG. 9 is a diagram corresponding to FIG. 6, in which the first transmission characteristic information corresponding to the reference temperature is indicated by a curve CL1, and the second transmission characteristic information corresponding to the reference temperature is indicated by a curve CL2. Is shown. Further, the transmission characteristic of the first optical filter 63a at the filter temperature estimated in step S6 is indicated by a curve CL1 ′, and the transmission characteristic of the second optical filter 64a at the filter temperature is indicated by a curve CL2 ′. Yes.
By the way, in the transmission characteristic (curve CL1) of the first optical filter 63a, a portion corresponding to a peak or a valley (hereinafter referred to as a dead zone) has a small variation amount of the first PD ratio with respect to the variation amount of the wavelength. is there. For this reason, when wavelength adjustment control is performed using the dead zone in the first transmission characteristic information (curve CL1), it is difficult to control the wavelength of the laser light L1 to the target wavelength. The same applies to portions corresponding to peaks or valleys in the transmission characteristics (curve CL2) of the second optical filter 64a.

  Therefore, in the first embodiment, the transmission characteristics of the first and second optical filters 63a and 64a are shifted in phase from each other within a range of 1/3 to 1/5 of one cycle, for example. That is, the dead zone of the transmission characteristic (curve CL1) of the first optical filter 63a and the dead zone of the transmission characteristic (curve CL2) of the second optical filter 64a are set so as not to overlap each other. For this reason, when controlling the wavelength of the laser beam L1 to the target wavelength TW, among the first and second transmission characteristic information (curves CL1, CL2), the first transmission where the target wavelength TW is located in the dead zone. Instead of the characteristic information (curve CL1), the second transmission characteristic information (curve CL2) in which the target wavelength TW is not located in the dead zone can be used. At this time, the control reference value (first control target value PDT1) associated with the target wavelength TW in the first transmission characteristic information (curve CL1) and the target wavelength TW in the second transmission characteristic information (curve CL2) are associated. Of the obtained control reference values (second control target value PDT2), the one closer to the average value AV (second control target value PDT2) is selected. Thereby, when controlling the wavelength of the laser beam L1 to the target wavelength TW, the second transmission characteristic information (curve CL2) in which the target wavelength TW is not located in the dead zone can be used.

However, when the temperature of the second optical filter 64a deviates from the reference temperature, the entire transmission characteristic of the second optical filter 64a is shifted on the wavelength axis (shifted from the curve CL2 to the curve CL2 ′). That is, although the temperature of the second optical filter 64a is deviated from the reference temperature and the transmission characteristic of the second optical filter 64a is the curve CL2 ′, the second transmission characteristic corresponding to the reference temperature. When wavelength adjustment control is executed with the control reference value associated with the target wavelength TW in the information (curve CL2) as the second control target value PDT2, the wavelength of the laser light L1 is shifted from the target wavelength TW. It will be controlled by '.
Further, a correction value associated with the target wavelength TW in the second target value correction information corresponding to the filter temperature is added to the second control target value PDT2, thereby generating a second correction control target value PDT2 ′. Even when the wavelength adjustment control is executed using the second correction control target value PDT2 ′ as the target value of the second PD ratio (the transmission characteristic of the second optical filter 64a corresponding to the filter temperature (curve CL2 Even when ') is used), since the second correction control target value PDT2' is located in the dead zone, it is difficult to accurately control the laser light L1 to the target wavelength TW.

  Therefore, in the first embodiment, the storage unit 32 stores a plurality of target value correction information corresponding to a plurality of temperatures. The control device 3 estimates the filter temperatures of the first and second optical filters 63a and 64a, refers to the first and second target value correction information corresponding to the filter temperatures, and The first and second control target values PDT1 and PDT2 are corrected by using the correction values CV1 and CV2 associated with the target wavelength TW in the target value correction information of 2, and the first and second correction control targets. Values PDT1 ′ and PDT2 ′ are generated. Furthermore, the control device 3 selects the first correction control target value PDT1 ′ that is close to the average value AV among the first and second correction control target values PDT1 ′ and PDT2 ′. Then, the control device 3 performs wavelength adjustment control so that the first PD ratio matches the first correction control target value PDT1 ′.

  When calculating the power (initial power) supplied to each of the micro heaters 421 to 423 with reference to the wavelength power information, the first and second control target values PDT1, PDT2 are calculated with reference to the transmission characteristic information. When calculating the correction value with reference to the target value correction information, when the target wavelength TW is not any of the wavelengths λ1 to λn, the power (initial power), the first power is obtained by linear interpolation or the like. The first control target value or the correction value may be calculated.

According to the first embodiment described above, the following effects are obtained.
In the wavelength tunable laser device 1 according to the first embodiment, the first and second control target values PDT1 and PDT2 are corrected using the target value correction information corresponding to the filter temperature. For this reason, even when the filter temperatures of the first and second optical filters 63a and 64a are deviated from the reference temperature, the first and second correction control target values PDT1 ′ and PDT2 ′ correspond to the target wavelength TW. Can be calculated with high accuracy as In the wavelength tunable laser device 1, a correction control target value close to the average value AV is selected from the first and second correction control target values PDT1 ′ and PDT2 ′, and wavelength adjustment control is performed using the correction control target value. Is running. For this reason, wavelength adjustment control can be executed using a correction control target value that is not located in the dead zone.
From the above, by executing the wavelength adjustment control so that the PD ratio having the correction control target value as the target value out of the first and second PD ratios matches the selected correction control target value. The wavelength of the laser beam L1 can be accurately controlled to the target wavelength TW.
In particular, when selecting one of the first and second correction control target values PDT1 ′ and PDT2 ′, a configuration is adopted in which the one closer to the average value AV is selected. For this reason, one of the first and second correction control target values PDT1 ′ and PDT2 ′ that are not located in the dead zone can be selected by a simple calculation, and the processing load on the control unit 31 can be reduced.

In the wavelength tunable laser device 1 according to the first embodiment, when correcting the first and second control target values PDT1 and PDT2, a plurality of wavelengths and a plurality of correction values are associated with each other at a plurality of temperatures. A plurality of target value correction information obtained is used. In the wavelength tunable laser device 1, when the target value correction information at the same temperature as the filter temperature is not stored in the storage unit 32, a plurality of corrections associated with the target wavelengths TW in the plurality of target value correction information. A correction value is generated from the value by interpolation, and the first and second control target values PDT1 and PDT2 are corrected using the correction value.
For this reason, the data amount of several target value correction information for correct | amending the 1st, 2nd control target value PDT1, PDT2 can be decreased.

  In the wavelength tunable laser device 1 according to the first embodiment, the temperature of the wavelength tunable light source unit 4, the semiconductor optical amplifier 5, the planar lightwave circuit 6, and the light detection unit 7 is controlled by only one temperature controller 9. Adjust. Thus, when it is set as the structure which adjusts the temperature of the said members 4-7 by only one temperature regulator 9, compared with the case where a several temperature regulator is provided, reduction in power consumption and a small size. Can be achieved. On the other hand, when only one temperature controller 9 is used, there is a risk of being affected by the temperature distribution generated in the plane of the installation surface 91. In particular, the wavelength variable unit 42 includes microheaters 421 to 423 that locally heat the light source unit 41. For this reason, temperature distribution tends to occur in the plane of the installation surface 91. That is, even when the temperature sensor 8 is disposed at a position close to the planar lightwave circuit 6, the temperature detected by the temperature sensor 8 is flat because it is affected by heat transfer from the microheaters 421 to 423. The temperature does not coincide with the temperature of the light wave circuit 6 (first and second optical filters 63a and 64a). That is, it is difficult to measure the temperatures of the first and second optical filters 63a and 64a.

  Therefore, in the wavelength tunable laser device 1 according to the first embodiment, the ambient temperature detected by the temperature sensor 8, the power associated with the target wavelength TW among the plurality of powers in the wavelength power information, and the thermal resistance information Based on the above, the filter temperature is estimated. For this reason, the filter temperature can be accurately estimated in consideration of the influence of heat transfer from the micro heaters 421 to 423. Therefore, the target value correction information corresponding to the filter temperature with high accuracy can be used, and the effect that the wavelength of the laser light L1 can be accurately controlled to the target wavelength TW can be preferably realized. .

(Embodiment 2)
Next, the second embodiment will be described.
In the following description, the same reference numerals are given to the same components as those in the first embodiment described above, and detailed description thereof will be omitted or simplified.
FIG. 10 is a block diagram showing the configuration of the control device 3A according to the second embodiment. FIG. 11 is a flowchart showing a wavelength control method by the control device 3A.
In the wavelength tunable laser device 1A according to the second embodiment, a control device 3A that performs wavelength lock control using a method different from that of the control device 3 with respect to the wavelength tunable laser device 1 described in the first embodiment described above. Adopted.
In the control device 3A, the function of the target value correcting unit 314 and the information stored in the storage unit 32 are different from the control device 3 described in the first embodiment.
Hereinafter, for convenience of explanation, the control unit (target value correction unit) and the storage unit according to the second embodiment are referred to as a control unit 31A (target value correction unit 314A) and a storage unit 32A, respectively.

The storage unit 32A stores a program executed by the control unit 31A, information necessary for processing of the control unit 31A, and the like. In addition to the thermal resistance information, wavelength power information, transmission characteristic information, and reference value information described in the first embodiment, the storage unit 32A includes temperature characteristic information and information necessary for processing by the control unit 31A. Stores slope information.
The temperature characteristic information is information indicating temperature characteristics in the first and second optical filters 63a and 64a. Specifically, as described above, the transmission characteristics of the first and second optical filters 63a and 64a are generally shortwave on the wavelength axis when the temperature of the first and second optical filters 63a and 64a changes. Shift to the side or long wave side. The temperature characteristic information is information indicating a wavelength shift amount X [nm / ° C.] at which the transmission characteristic shifts per unit temperature.

FIG. 12 is a diagram for explaining the slope information stored in the storage unit 32A. Specifically, FIG. 12 is a diagram corresponding to FIGS. 6 and 9.
The slope information is information indicating transmission characteristics in the first and second optical filters 63a and 64a. Specifically, the slope information is the variation in wavelength within the range between the upper limit UL and the lower limit LL excluding the dead zone (hereinafter referred to as the slope portion) in the transmission characteristic (curve CL1) of the first optical filter 63a. This is information indicating the ratio of the variation amount of the first PD ratio to the amount (the slope of the slope portion). The transmission characteristics of the first and second optical filters 63a and 64a are only shifted in phase from each other. For this reason, the slope of the slope portion in the transmission characteristic (curve CL2) of the second optical filter 64a is the same as the slope of the slope portion in the transmission characteristic (curve CL1) of the first optical filter 63a.
Hereinafter, the function of the target value correction unit 314A will be described with reference to FIG.

In the wavelength control method by the control device 3A, as shown in FIG. 11, steps S10 to S13 are employed instead of step S7, compared to the wavelength control method (FIG. 8) described in the first embodiment. The point is different. Only steps S10 to S13 will be described below. Steps S10 to S13 correspond to a target value correction step according to the present invention.
Step S10 is executed after step S6.
Specifically, the target value correction unit 314A calculates a temperature difference δT between the filter temperature estimated in step S6 and the reference temperature (step S10).
After step S10, the target value correcting unit 314A uses the temperature characteristic information (wavelength deviation amount X [nm / ° C.] per unit temperature) stored in the storage unit 32A and the temperature difference δT calculated in step S10. Based on this, a wavelength shift amount (X × δT) corresponding to the temperature difference δT is calculated (step S11).

After step S11, the target value correction unit 314A performs step based on the wavelength shift amount (X × δT) corresponding to the temperature difference δT calculated in step S11 and the slope information stored in the storage unit 32A. Each correction value for correcting the first and second control target values PDT1, PDT2 calculated in S2 is calculated (step S12). In FIG. 12, only the correction value CV1 for generating the first correction control target value PDT1 ′ by adding to the first control target value PDT1 is shown for convenience of explanation.
After step S12, the target value correction unit 314A adds the correction values calculated in step S12 to the first and second control target values PDT1 and PDT2 calculated in step S2, respectively. 2 correction control target values PDT1 ′ and PDT2 ′ are generated (step S13). Thereafter, the control device 3A proceeds to step S8.
In FIG. 11, for the sake of convenience of explanation, the flow for completing the wavelength lock control after step S9 is shown. However, actually, after step S9, the process returns to step S4, and steps S4 to S6, S10 to S13, S8. , S9 is repeated to control the wavelength of the laser light L1 to the target wavelength TW.

Even when the first and second control target values PDT1 and PDT2 are corrected as in the second embodiment described above, the same effects as those in the first embodiment are obtained.
In addition, since it is not necessary to store a plurality of target value correction information in the storage unit 32A, the amount of data stored in the storage unit 32A can be reduced.

(Embodiment 3)
Next, the third embodiment will be described.
In the following description, the same reference numerals are given to the same components as those in the first embodiment described above, and detailed description thereof will be omitted or simplified.
FIG. 13 is a block diagram illustrating a configuration of a control device 3B according to the third embodiment. FIG. 14 is a flowchart showing a wavelength control method by the control device 3B.
In the wavelength tunable laser device 1B according to the third embodiment, a control device 3B that performs wavelength lock control by a method different from that of the control device 3 with respect to the wavelength tunable laser device 1 described in the first embodiment described above. Adopted.
In the control device 3B, the function of the temperature estimation unit 311 and the information stored in the storage unit 32 are different from those of the control device 3 described in the first embodiment. In addition, the temperature sensor 8 is not provided in the wavelength tunable laser device 1B in accordance with the change in the function of the temperature estimation unit 311.
Hereinafter, for convenience of explanation, the control unit (temperature estimation unit) and the storage unit according to the third embodiment are referred to as a control unit 31B (temperature estimation unit 311B) and a storage unit 32B, respectively.

The storage unit 32B stores a program executed by the control unit 31B, information necessary for processing of the control unit 31B, and the like. In addition to the wavelength power information, the transmission characteristic information, the plurality of target value correction information, and the reference value information described in the first embodiment, the storage unit 32B includes a plurality of pieces of information necessary for the processing of the control unit 31B. A plurality of temperature estimation information provided for each wavelength is stored.
The temperature estimation information is information for estimating the filter temperature. Specifically, the temperature estimation information is the output value of the electrical signal output from the PD 72 with respect to the output value of the electrical signal output from the PD 71 when the wavelength of the laser beam L1 is set to wavelengths λ1 to λn [nm], respectively. Deviation between each first PD ratio, which is a ratio of the first, and each first control target value corresponding to the wavelengths λ1 to λn (difference between the first control target value and the first PD ratio), and a plurality of Is associated with each temperature.
Hereinafter, the function of the temperature estimation unit 311B will be described with reference to FIG.

  In the wavelength control method by the control device 3B, as shown in FIG. 14, step S5 is omitted from the wavelength control method described in the first embodiment (FIG. 8), and instead of step S6. The difference is that step S14 is employed. Only step S14 will be described below. Step S14 corresponds to a temperature estimation step according to the present invention.

Step S14 is executed after step S4.
Specifically, the temperature estimation unit 311B corresponds to the target wavelength TW (corresponding to the first wavelength according to the present invention) acquired in step S1 among the plurality of temperature estimation information stored in the storage unit 32B. Read temperature estimation information. Then, the temperature estimation unit 311B refers to the temperature estimation information corresponding to the target wavelength TW, and the first control target value PDT1 (corresponding to the expected monitor value according to the present invention) calculated in step S2 and step S4. The temperature associated with the difference from the first PD ratio calculated in (5) is estimated as the filter temperature (step S14). Thereafter, the control device 3B proceeds to step S7.
In FIG. 14, for the sake of convenience of explanation, the flow of completing the wavelength lock control after step S9 is shown, but actually, after step S9, the process returns to step S4, and the loop of steps S4 and S9 (steps S14, S9) By repeating (S7 and S8 are not executed), the wavelength of the laser light L1 is controlled to the target wavelength TW. That is, in the third embodiment, when the wavelength tunable laser device 1B is activated, the filter temperature is estimated (step S14), the first and second control target values PDT1 and PDT2 are corrected (step S7), and the first and first One of the two correction control target values PDT1 ′ and PDT2 ′ is executed (step S8), and in the subsequent loop of steps S4 and S9, the wavelength adjustment control is performed using the correction control target value selected in step S8. Execute.

  Here, the first transmission characteristic information corresponds to the expected monitor value information according to the present invention. Note that the expected monitor value information according to the present invention is not limited to the first transmission characteristic information, and may be second transmission characteristic information. At this time, the temperature estimation information includes the output value of the electrical signal output from the PD 73 with respect to the output value of the electrical signal output from the PD 71 when the wavelength of the laser beam L1 is set to the wavelengths λ1 to λn [nm], respectively. A deviation amount between each second PD ratio as a ratio and each second control target value corresponding to the wavelengths λ1 to λn (difference between the second control target value and the second PD ratio), and a plurality of This is information associated with each temperature. In step S14, the temperature estimation unit 311B refers to the temperature estimation information corresponding to the target wavelength TW (corresponding to the first wavelength according to the present invention), and the second control target value calculated in step S2. The temperature associated with the difference between PDT2 (corresponding to the expected monitor value according to the present invention) and the second PD ratio calculated in step S4 is estimated as the filter temperature.

Even when the filter temperature is estimated as in the third embodiment described above, the same effects as those in the first embodiment described above can be obtained.
Moreover, since the temperature sensor 8 can be omitted, the structure of the wavelength tunable laser device 1B can be simplified.

(Embodiment 4)
Next, the fourth embodiment will be described.
In the following description, the same reference numerals are given to the same components as those in the first embodiment described above, and detailed description thereof will be omitted or simplified.
FIG. 15 is a block diagram showing a configuration of a control device 3C according to the fourth embodiment. FIG. 16 is a flowchart illustrating a wavelength control method by the control device 3C.
In the wavelength tunable laser device 1C according to the fourth embodiment, a control device 3C that performs wavelength lock control by a method different from the control device 3 is used with respect to the wavelength tunable laser device 1 described in the first embodiment. Adopted.
In the control device 3C, the function of the target value selection unit 315 and the information stored in the storage unit 32 are different from those of the control device 3 described in the first embodiment.
Hereinafter, for convenience of explanation, the control unit (target value selection unit) and the storage unit according to the fourth embodiment are referred to as a control unit 31C (target value selection unit 315C) and a storage unit 32C, respectively.

The storage unit 32C stores a program executed by the control unit 31C, information necessary for processing of the control unit 31C, and the like. Note that the storage unit 32C has, as information necessary for the processing of the control unit 31C, the thermal resistance information, wavelength power information, transmission characteristic information, multiple target value correction information, and reference value information described in the first embodiment. In addition, the fluctuation range information is stored.
The fluctuation range information is information indicating a fluctuation range of the first correction control target value PDT1 ′ or the second correction control target value PDT2 ′.
Hereinafter, the function of the target value selection unit 315C will be described with reference to FIG.

In the wavelength control method by the control device 3C, as shown in FIG. 16, steps S15 to S17 are employed instead of step S8, compared to the wavelength control method (FIG. 8) described in the first embodiment. The point is different. Only steps S15 to S17 will be described below. Steps S15 to S17 correspond to a target value selection step according to the present invention.
Here, in FIG. 16, for convenience of explanation, a flow for completing the wavelength lock control after step S9 is shown, but actually, after step S9, the process returns to step S4, and steps S4 to S7, S15 to S17, By repeating the loop of S9, the wavelength of the laser light L1 is controlled to the target wavelength TW.

Step S15 is executed after step S7.
Specifically, the target value selection unit 315C refers to the variation range information stored in the storage unit 32C, and performs the correction control within the variation range based on the variation range information centered on the correction control target value selected immediately before. It is determined whether or not a newly generated correction control target value corresponding to the target value has been entered (step S15). The “correction control target value selected immediately before” means the correction control target value selected in steps S16 and S17 in the immediately preceding loop (steps S4 to S7, S15 to S17, and S9). The “correction control target value corresponding to the correction control target value and newly generated” is the case where the first correction control target value PDT1 ′ is selected in steps S16 and S17 in the immediately preceding loop. Means the first correction control target value PDT1 ′ newly generated in step S7 (step S7 in the current loop (the loop next to the previous loop)), and steps S16 and S17 in the previous loop. When the second correction control target value PDT2 ′ is selected in step S7, the second correction newly generated in step S7 (step S7 in the current loop (the loop next to the immediately preceding loop)). This means the control target value PDT2 ′.

When it is determined that the newly generated correction control target value is within the fluctuation range (step S15: Yes), the target value selection unit 315C corrects the correction separately from the newly generated correction control target value. Even if the control target value is closer to the average value AV, the newly generated corrected control target value is selected (step S16). Thereafter, the control device 3C proceeds to step S9. The “correction control target value different from the newly generated correction control target value” is the first value when the newly generated correction control target value is the first correction control target value PDT1 ′. 2 when the newly generated correction control target value is the second correction control target value PDT2 ′, it means the first correction control target value PDT1 ′.
On the other hand, when it is determined that the newly generated correction control target value is not included in the fluctuation range (step S15: No), the target value selection unit 315C performs step S8 described in the first embodiment. Similarly, a correction control target value close to the average value AV is selected from the first and second correction control target values PDT1 ′ and PDT2 ′ generated in step S7 (step S17). Thereafter, the control device 3C proceeds to step S9.

  17 and 18 are diagrams for explaining the wavelength control method. Specifically, FIG. 17 is a diagram corresponding to FIG. 6 and FIG. 9, in which first transmission characteristic information corresponding to the reference temperature is indicated by a curve CL1, and second transmission characteristic information corresponding to the reference temperature is shown. Is indicated by a curve CL2. Further, the transmission characteristic of the first optical filter 63a when the temperature of the first optical filter 63a is increased by ΔT from the reference temperature is shown by a curve CL1U (FIG. 17A). Further, the transmission characteristic of the first optical filter 63a when the temperature of the first optical filter 63a is reduced by ΔT from the reference temperature is shown by a curve CL1D (FIG. 17B). Further, the transmission characteristic of the second optical filter 64a when the temperature of the second optical filter 64a is increased by ΔT from the reference temperature is shown by a curve CL2U (FIG. 17A). Further, the transmission characteristic of the second optical filter 64a when the temperature of the second optical filter 64a is reduced by ΔT from the reference temperature is shown by a curve CL2D (FIG. 17B). FIG. 18 is an enlarged view of a part of the curves CL2, CL2U, CL2D in FIGS. 17 (a) and 17 (b).

  By the way, if the loop of steps S4 to S7, S15 to S17, and S9 is repeatedly executed, the filter temperature estimated in step S6 is also determined according to the minute fluctuation of the ambient temperature around the wavelength tunable laser apparatus 1C. Shake. ΔT mentioned above means the fluctuation amount of the filter temperature. Then, for example, as shown in FIG. 17A, when the filter temperature is the reference temperature + ΔT, the second correction control target value PDT2 ′ is an average value than the first correction control target value PDT1 ′. Since it is close to AV, the second correction control target value PDT2 ′ is selected. On the other hand, as shown in FIG. 17B, in the state where the filter temperature is the reference temperature −ΔT, the first correction control target value PDT1 ′ has an average value AV rather than the second correction control target value PDT2 ′. Since the values are close, the first correction control target value PDT1 ′ is selected. That is, when the loop of steps S4 to S7, S15 to S17, and S9 is repeatedly executed, the correction control target value that is selected according to the minute fluctuation of the ambient temperature around the wavelength tunable laser device 1C is frequently set. It will be switched.

  Therefore, in the fourth embodiment, the storage unit 32C stores the fluctuation range of the first correction control target value or the second correction control target value (between the fluctuation upper limit value FUL and the fluctuation lower limit value FDL shown in FIG. 17). The variation range information indicating the range FR) is stored. When the newly generated correction control target value is entered in the fluctuation range FR centered on the correction control target value PDT ′ selected immediately before, the control device 3C Even when a correction control target value different from the correction control target value generated in the step is closer to the average value AV, the newly generated correction control target value is selected. Then, the control device 3C controls the wavelength adjustment so that the PD ratio having the correction control target value as the target value out of the first and second PD ratios matches the newly generated correction control target value. Execute.

Here, the fluctuation range FR based on the fluctuation range information is set as shown below.
That is, when the filter temperature is shifted by ΔT from the reference temperature, the wavelength shift amount corresponding to ΔT of the transmission characteristics in the first and second optical filters 63a and 64a has been described in the above-described second embodiment. Using the temperature characteristic information (wavelength shift amount X [nm / ° C.] per unit temperature, it becomes the shift amount (X × ΔT) as shown in FIG. 18. Also, the fluctuation upper limit value FUL or the fluctuation lower limit value FDL And the center position (correction control target value PDT ′) of the fluctuation range FR are the wavelength shift amount (X × ΔT) corresponding to the ΔT and the slope information described in the second embodiment. In other words, the fluctuation range FR is set with the double of the width as a minimum range.

Even when the correction control target value is selected as in the fourth embodiment described above, the same effects as those in the first embodiment described above can be obtained.
Further, it is possible to suppress frequent switching of the selected correction control target value with respect to minute fluctuations in the environmental temperature around the wavelength tunable laser apparatus 1C.

(Embodiment 5)
Next, the fifth embodiment will be described.
In the following description, the same reference numerals are given to the same components as those in the first embodiment described above, and detailed description thereof will be omitted or simplified.
FIG. 19 is a block diagram showing a configuration of a control device 3D according to the fifth embodiment. FIG. 20 is a flowchart illustrating a wavelength control method by the control device 3D.
In the wavelength tunable laser device 1D according to the fifth embodiment, a control device 3D that performs wavelength lock control using a method different from that of the control device 3 with respect to the wavelength tunable laser device 1 described in the first embodiment described above. Adopted.
In the control device 3D, the functions of the target value correction unit 314 and the target value selection unit 315 are different from those of the control device 3 described in the first embodiment.
Hereinafter, for convenience of explanation, the control unit (target value correction unit and target value selection unit) according to the fifth embodiment is referred to as a control unit 31D (target value correction unit 314D and target value selection unit 315D).
Hereinafter, functions of the target value correcting unit 314D and the target value selecting unit 315D will be described with reference to FIG.

As shown in FIG. 20, the wavelength control method by the control device 3D is different from the wavelength control method described in the first embodiment (FIG. 8) in that steps S18 to S21 are added. Only steps S18 to S21 will be described below.
Step S18 is executed after step S6.
Specifically, the control unit 31D determines whether or not the temperature difference between the filter temperature estimated in step S6 and the reference temperature is smaller than a threshold value (step S18).
Here, in step S18, the determination of “No” is made because the wavelength shift amount corresponding to the temperature difference between the filter temperature and the reference temperature is relatively small in the transmission characteristics of the first and second optical filters 63a and 64a. It means big. That is, even if the first control target value PDT1 or the second control target value PDT2 is not located in the dead zone, the first correction control target value PDT1 ′ or the second correction control target value PDT2 ′ is located in the dead zone. It means that there is a high possibility of doing.
On the other hand, in step S18, the determination of “Yes” means that the wavelength shift amount corresponding to the temperature difference between the filter temperature and the reference temperature is relatively small. That is, if the first control target value PDT1 or the second control target value PDT2 is not located in the dead zone, the first correction control target value PDT1 ′ or the second correction control target value PDT2 ′ is not located in the dead zone. It means that the possibility is high.

  When it is determined that the temperature difference between the filter temperature and the reference temperature is greater than or equal to the threshold value (step S18: No), the first and second target value correction units 314D perform the first and second operations as in the first embodiment described above. Correction of control target values PDT1 and PDT2 (step S7), selection of one of the first and second correction control target values PDT1 ′ and PDT2 ′ by the target value selection unit 315D (step S8), and the wavelength by the operation control unit 316 Adjustment control (step S9) is sequentially executed.

On the other hand, when it is determined that the temperature difference between the filter temperature and the reference temperature is smaller than the threshold value (step S18: Yes), the target value selection unit 315D performs the first and second calculations calculated in step S2. Of the control target values PDT1 and PDT2, the control target value closer to the average value AV based on the reference value information stored in the storage unit 32 is selected (step S19: target value selection step).
After step S19, the target value correction unit 314D refers to the target value correction information corresponding to the filter temperature estimated in step S6, corrects the control target value selected in step S19, and corrects the corrected control target value. Is generated (step S20: target value correcting step). In step S20, both the first and second control target values PDT1 and PDT2 are corrected in step S7, whereas the control target selected in step S19 is different from step S7. The only difference is that only the values are corrected.

After step S20, the operation control unit 316 uses the correction control target value of the first and second PD ratios calculated in step S4 for the correction control target value generated in step S20. Wavelength adjustment control is performed to change the power supplied to each of the micro heaters 421 to 423 so that the PD ratio as the target value matches (step S21: operation control step). The “PD ratio with the correction control target value as a target value” means the first PD ratio when the first control target value PDT1 is selected in step S19, and the process proceeds to step S19. When the second control target value PDT2 is selected, it means the second PD ratio.
In FIG. 20, for the sake of convenience of explanation, after Steps S9 and S21, the flow for completing the wavelength lock control is shown. However, actually, after Steps S9 and S21, the process returns to Step S4, and Steps S4 to S6 and S18. , S7 to S9, or steps S4 to S6 and S18 to S21 are repeated to control the wavelength of the laser light L1 to the target wavelength TW.

  Even when the wavelength lock control is executed as in the fifth embodiment described above, the same effects as in the first embodiment described above can be obtained.

(Other embodiments)
Up to this point, the mode for carrying out the present invention has been described. However, the present invention should not be limited only by the first to fifth embodiments.
In the first to fifth embodiments described above, the ring resonator type optical filters 63a and 64a are employed as the first and second optical filters according to the present invention, but the present invention is not limited to this. Other optical filters such as an etalon may be employed as the first and second optical filters according to the present invention as long as the optical filter has periodic transmission characteristics with respect to the wavelength of incident light. Further, the number of optical filters is not limited to two, and may be three or more.

In the first to fifth embodiments described above, the positions where the first and second optical filters and the first to third light receiving elements according to the present invention are disposed are the positions described in the first to fifth embodiments. Not limited to. For example, an optical branching unit that branches the laser beam L1 output from the wavelength variable light source unit 4 into two laser beams and outputs one of the laser beams to the semiconductor optical amplifier 5 is provided. Then, the first and second optical filters and the first to third light receiving elements according to the present invention may be disposed at a position for receiving the other laser beam branched by the optical branching unit.
In the first, second, fourth, and fifth embodiments described above, when the temperature sensor 8 is placed on the temperature controller 9, the arrangement position is not limited to the second region Ar2, but the first region Ar1. Also good. The filter temperature estimation method is not limited to the method using the thermal resistance information and the wavelength power information described in the first, second, fourth, and fifth embodiments, and other methods may be employed. In particular, the ambient temperature itself detected by the temperature sensor 8 may be estimated as the filter temperature.

In Embodiments 1 to 5 described above, only one average value AV is employed as the first and second reference value information according to the present invention. However, the present invention is not limited to this. For example, when the transmission characteristics of the first and second optical filters 63a and 64a have different characteristics due to manufacturing variations, the following configuration may be employed.
First and second reference value information is stored in the storage units 32 and 32A to 32C. Here, the first reference value information is the electric power output from the PD 71 when the wavelength of the light incident on the first optical filter 63a is changed by one period in the transmission characteristic of the first optical filter 63a. This is information indicating the average value (first average value) of each first PD ratio, which is the ratio of the output value of the electrical signal output from the PD 72 to the output value of the signal. On the other hand, the second reference value information is an electrical signal output from the PD 71 when the wavelength of light incident on the second optical filter 64a is changed by one period in the transmission characteristic of the second optical filter 64a. This is information indicating the average value (second average value) of each second PD ratio, which is the ratio of the output value of the electrical signal output from the PD 73 to the output value of. Then, the target value selection units 315, 315C, and 315D perform the second correction and the difference between the first correction control target value PDT1 ′ (first control target value PDT1 in the case of step S19) and the first average value. Of the difference between the control target value PDT2 ′ (second control target value PDT2 in the case of step S19) and the second average value, the correction control target value having a small difference (control target value in the case of step S19). ) Is selected. Here, the “correction control target value with a small difference (control target value in the case of step S19)” is the first correction control target value PDT1 ′ (first control target value PDT1 in the case of step S19). ) And the difference between the first average value is smaller than the difference between the second correction control target value PDT2 ′ (the second control target value PDT2 in the case of step S19) and the second average value. It means the first correction control target value PDT1 ′ (first control target value PDT1 in the case of step S19), and the second correction control target value PDT2 ′ (second control target value in the case of step S19). PDT2) and the difference between the second average value are smaller than the difference between the first correction control target value PDT1 ′ (first control target value PDT1 in the case of step S19) and the first average value. Is the second correction control target value PD T2 ′ (second control target value PDT2 in the case of step S19) is meant.

  You may combine the structure of Embodiment 1-5 mentioned above suitably. For example, the first and second control target values PDT1 and PDT2 described in the second embodiment described above are applied to the configurations of the third to fifth embodiments described above (such as the function of the target value correcting unit 314A). It doesn't matter. Further, the filter temperature estimation method (the function of the temperature estimation unit 311B and the like) described in the third embodiment may be applied to the configurations of the second, fourth, and fifth embodiments described above.

DESCRIPTION OF SYMBOLS 1,1A-1D Wavelength variable laser apparatus 2 Wavelength variable laser module 3, 3A-3D Control apparatus 4 Wavelength variable light source part 5 Semiconductor optical amplifier 6 Planar light wave circuit 7 Light detection part 8 Temperature sensor 9 Temperature controller 31, 31A-31D Control unit 32, 32A to 32C Storage unit 41 Light source unit 42 Wavelength variable unit 43 First waveguide unit 44 Second waveguide unit 44a Optical waveguide layer 45 n-side electrode 61 Optical branching unit 62 Optical waveguide 63 Optical waveguide 63a Ring Resonator type optical filter (first optical filter)
64 Optical waveguide 64a Ring resonator type optical filter (second optical filter)
71-73 PD
91 Installation surface 311, 311B Temperature estimation unit 312 Monitor value calculation unit 313 Target value calculation unit 314, 314A, 314D Target value correction unit 315, 315C, 315D Target value selection unit 316 Operation control unit 421-423 Micro heater 431 Waveguide unit 431a Gain section 431b Diffraction grating layer 432 Semiconductor laminated section 433 P-side electrode 441 Two-branch section 441a Multimode interference type waveguide 442, 443 Arm section 444 Ring-shaped waveguide 445 Phase adjustment section Ar1 First area Ar2 Second area AV average value B1 base C1 optical resonator CL1, CL1 ′, CL1U, CL1D, CL2, CL2 ′, CL2U, CL2D curve CV1, CV2 correction value FR fluctuation range FDL fluctuation lower limit value FUL fluctuation upper limit value L1 to L6 laser light LL lower limit Value M1 Reflective mirror PDT ' Positive control target value PDT1 first control target value PDT1' first correction control target value PDT2 second control target value PDT2' second correction control target value RF1 ring resonator filter TW target wavelength TW' wavelength UL upper limit

Claims (11)

A wavelength tunable light source unit that makes the wavelength of the laser beam to be output variable;
A first light receiving element for acquiring the intensity of the laser beam output from the wavelength variable light source unit;
A first optical filter having a first transmission characteristic whose characteristics periodically change with respect to the wavelength of incident light;
A second light receiving element for acquiring the intensity of the laser light transmitted through the first optical filter;
A second optical filter having a second transmission characteristic whose characteristic changes periodically with respect to the wavelength of the incident light;
A third light receiving element for acquiring the intensity of the laser light transmitted through the second optical filter;
A control device for controlling the operation of the wavelength variable light source unit,
The controller is
A temperature estimation unit for estimating a filter temperature of the first optical filter and the second optical filter;
The first monitor value is calculated based on the intensity of the laser light acquired by the first light receiving element and the second light receiving element, and the laser acquired by the first light receiving element and the third light receiving element. A monitor value calculation unit for calculating a second monitor value based on the intensity of light;
Based on the filter temperature, the first control target value corresponding to the target wavelength of the laser light and the target of the first monitor value is corrected to generate a first correction control target value, and the target A target value correcting unit that generates a second corrected control target value by correcting the second control target value that corresponds to the wavelength and that is the target of the second monitor value;
A target value selection unit that selects one of the first correction control target value and the second correction control target value;
Based on the correction control target value selected by the target value selection unit, and the monitor value having the correction control target value as a target value among the first monitor value and the second monitor value, the wavelength A wavelength tunable laser apparatus comprising: an operation control unit configured to control the wavelength of laser light output from the variable light source unit to the target wavelength. The controller is
A storage unit for storing a plurality of target value correction information provided for each of a plurality of temperatures;
The target value correction information is
Information that associates multiple wavelengths with multiple correction values.
The target value correction unit
The target value correction information corresponding to the filter temperature is referred to among the plurality of target value correction information, and the correction value associated with the target wavelength among the plurality of correction values in the target value correction information is used. The wavelength tunable laser device according to claim 1, wherein the first control target value and the second control target value are corrected. The target value correction unit
A correction value is generated by interpolation from a plurality of correction values associated with the target wavelength in the plurality of target value correction information, and the first control target value and the second control are generated using the generated correction value. The wavelength tunable laser device according to claim 2, wherein the target value is corrected. The controller is
A storage unit for storing temperature characteristic information indicating temperature characteristics in the first optical filter and the second optical filter, and slope information indicating the first transmission characteristic and the second transmission characteristic;
The temperature characteristic information is
It is information indicating the amount of wavelength shift per unit temperature.
The slope information is
Information indicating the ratio of the fluctuation amount of the first monitor value and the second monitor value to the fluctuation amount of the wavelength of light incident on the first optical filter and the second optical filter,
The target value correction unit
A correction value is generated based on the temperature difference between the filter temperature and the reference temperature, the temperature characteristic information, and the slope information, and the first control target value and the second value are generated using the generated correction value. The wavelength tunable laser device according to claim 1, wherein the control target value is corrected. The controller is
A storage unit for storing first reference value information indicating the first transmission characteristic and second reference value information indicating the second transmission characteristic;
The first reference value information is
Information indicating a first average value of the first monitor values when the wavelength of light incident on the first optical filter is changed by one period in the first transmission characteristic;
The second reference value information is
Information indicating a second average value of the second monitor value when the wavelength of light incident on the second optical filter is changed by one period in the second transmission characteristic;
The target value selection unit
Of the difference between the first correction control target value and the first average value and the difference between the second correction control target value and the second average value, a correction control target value having a small difference is selected. The wavelength tunable laser device according to claim 1, wherein The storage unit
Further storing variation range information indicating the variation range,
The target value selection unit
The correction control target value newly generated by the target value correction unit and corresponding to the correction control target value selected immediately before is included in the fluctuation range centered on the correction control target value selected immediately before. In this case, even if a correction control target value different from the newly generated correction control target value is closer to the average value, the newly generated correction control target value is selected. The wavelength tunable laser device according to claim 5. The controller is
When the laser light having the first wavelength is input to the first optical filter, expected monitor value information indicating the expected monitor value corresponding to the first wavelength and expected as the first monitor value is stored. A storage unit
The temperature estimation unit
The filter temperature is estimated based on a difference between the first monitor value and the expected monitor value when laser light having the first wavelength is input to the first optical filter. The wavelength tunable laser device according to claim 1. A temperature sensor for detecting the ambient temperature of the wavelength tunable laser device;
The temperature estimation unit
The wavelength tunable laser apparatus according to claim 1, wherein the filter temperature is estimated based on the ambient temperature. A wavelength tunable light source unit that makes the wavelength of the laser beam to be output variable;
A first light receiving element for acquiring the intensity of the laser beam output from the wavelength variable light source unit;
A first optical filter having a first transmission characteristic whose characteristics periodically change with respect to the wavelength of incident light;
A second light receiving element for acquiring the intensity of the laser light transmitted through the first optical filter;
A second optical filter having a second transmission characteristic whose characteristic changes periodically with respect to the wavelength of the incident light;
A third light receiving element for acquiring the intensity of the laser light transmitted through the second optical filter;
A control device for controlling the operation of the wavelength variable light source unit,
The controller is
A temperature estimation unit for estimating a filter temperature of the first optical filter and the second optical filter;
The first monitor value is calculated based on the intensity of the laser light acquired by the first light receiving element and the second light receiving element, and the laser acquired by the first light receiving element and the third light receiving element. A monitor value calculation unit for calculating a second monitor value based on the intensity of light;
A first control target value corresponding to the target wavelength of the laser beam and serving as the target of the first monitor value, and a second control target value corresponding to the target wavelength and serving as the target of the second monitor value A target value selection unit that selects one of the control target values, and
A target value correcting unit that corrects the control target value selected by the target value selecting unit based on the filter temperature and generates a corrected control target value;
Laser light output from the wavelength tunable light source unit based on the correction control target value and a monitor value using the correction control target value as a target value among the first monitor value and the second monitor value And an operation control unit that controls the wavelength of the laser beam to the target wavelength. A wavelength tunable light source unit that makes the wavelength of the laser beam to be output variable, a first light receiving element that acquires the intensity of the laser beam output from the wavelength tunable light source unit, and the wavelength of the incident light A first optical filter having a first transmission characteristic whose characteristics change, a second light receiving element for acquiring the intensity of laser light transmitted through the first optical filter, and a period with respect to a wavelength of incident light Of a wavelength tunable laser apparatus comprising: a second optical filter having a second transmission characteristic whose characteristics change in nature; and a third light receiving element for acquiring the intensity of the laser light transmitted through the second optical filter. A wavelength control method comprising:
A temperature estimation step of estimating a filter temperature of the first optical filter and the second optical filter;
The first monitor value is calculated based on the intensity of the laser light acquired by the first light receiving element and the second light receiving element, and the laser acquired by the first light receiving element and the third light receiving element. A monitor value calculating step for calculating a second monitor value based on the light intensity;
Based on the filter temperature, the first control target value corresponding to the target wavelength of the laser light and the target of the first monitor value is corrected to generate a first correction control target value, and the target A target value correcting step for generating a second corrected control target value by correcting the second control target value corresponding to the wavelength and serving as the target of the second monitor value;
A target value selection step of selecting any one of the first correction control target value and the second correction control target value;
The wavelength variable based on the correction control target value selected in the target value selection step and the monitor value using the correction control target value as a target value among the first monitor value and the second monitor value. An operation control step of controlling the wavelength of the laser beam output from the light source unit to the target wavelength. A wavelength control method for a wavelength tunable laser device, comprising: A wavelength tunable light source unit that makes the wavelength of the laser beam to be output variable, a first light receiving element that acquires the intensity of the laser beam output from the wavelength tunable light source unit, and the wavelength of the incident light A first optical filter having a first transmission characteristic whose characteristics change, a second light receiving element for acquiring the intensity of laser light transmitted through the first optical filter, and a period with respect to a wavelength of incident light Of a wavelength tunable laser apparatus comprising: a second optical filter having a second transmission characteristic whose characteristics change in nature; and a third light receiving element for acquiring the intensity of the laser light transmitted through the second optical filter. A wavelength control method comprising:
A temperature estimation step of estimating a filter temperature of the first optical filter and the second optical filter;
The first monitor value is calculated based on the intensity of the laser light acquired by the first light receiving element and the second light receiving element, and the laser acquired by the first light receiving element and the third light receiving element. A monitor value calculating step for calculating a second monitor value based on the light intensity;
A first control target value corresponding to the target wavelength of the laser beam and serving as the target of the first monitor value, and a second control target value corresponding to the target wavelength and serving as the target of the second monitor value A target value selection step for selecting one of the control target values of
A target value correcting step for correcting the control target value selected in the target value selecting step based on the filter temperature and generating a corrected control target value;
Laser light output from the wavelength tunable light source unit based on the correction control target value and a monitor value using the correction control target value as a target value among the first monitor value and the second monitor value And an operation control step of controlling the wavelength of the wavelength to the target wavelength.

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