Control device, light source device, optical transmission module, optical transceiver, and control method

Abstract

In order to enable oscillation of transmission light at an arbitrary oscillation frequency even in an environment in which the environment temperature is greatly different from an assumed temperature, a control device for a light source including a tunable filter is provided, comprising: a temperature reception means for receiving substrate temperature information indicating a substrate temperature of a substrate on which the light source is provided, and housing temperature information indicating a housing temperature of a housing containing the substrate; and a control means for controlling, on the basis of the substrate temperature information and the housing temperature information, the substrate temperature and the refraction index of the tunable filter so that the frequency of the transmission light the light source outputs becomes a desired frequency.

Description

Technical Field

[0001] The present invention relates to a control device and the like.

Background Art

[0002] In recent years, with the sophistication and diversification of information and communication services, optical communication systems are required to have a large capacity. Therefore, in optical communication systems, a wavelength division multiplexing (WDM) method that can increase the transmission capacity per optical fiber is adopted. And in wavelength division multiplexing (WDM) communication, an optical transceiver equipped with a wavelength variable laser using a plurality of wavelength variable filters that can oscillate at an arbitrary wavelength from among the wavelength bands used is used. An example of such an optical transceiver is described in Patent Document 1.

[0003] Also, as related technologies, there are the technologies described in Patent Documents 2-3.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described in Patent Document 1, silicon photonics technology can miniaturize optical functional elements typified by wavelength-variable filters by means of high-density optical wiring with a high refractive index. Among wavelength-variable filters using silicon photonics technology, there are waveguide-type filters that utilize the resonance effect of light, such as ring filters and grating filters. When this silicon photonics technology is used in an optical transceiver, it is possible to miniaturize an optical transceiver that uses a plurality of wavelength-variable filters. Therefore, applying an optical transceiver based on silicon photonics technology to an optical wavelength-variable light source module for communication has been studied. Usually, an optical wavelength-variable light source module for communication operates at a specific frequency standardized by the ITU (International Telecommunication Union), and the frequency deviation needs to be within the range of several GHz. However, in an optical wavelength light source module based on silicon photonics technology, the oscillation frequency is likely to change due to the influence of temperature. Therefore, the optical wavelength light source module is arranged on a temperature controller within a sealed package. Then, by controlling the temperature of the substrate to be constant by this temperature controller, the oscillation frequency of the optical wavelength light source module is controlled with high precision.

[0006] However, even if control is performed so that the temperature of the substrate becomes constant, when the environmental temperature changes from the assumed temperature, a certain temperature non-uniformity, although slight, occurs on the substrate. Note that the environmental temperature is the temperature of the environment in which the optical wavelength light source module is used. The assumed temperature is the temperature assumed as the environmental temperature. In the wavelength-variable filter of silicon photonics, even a small temperature change greatly affects the characteristics of the oscillation frequency. Also, depending on the temperature at the mounting position on the substrate, the characteristics of the transmission wavelength of each wavelength-variable filter change differently. As a result, the transmitted light may oscillate outside the target frequency range.

[0007] An object of the present invention is to provide a control device or the like that enables transmitted light to oscillate at an arbitrary oscillation frequency even in an environment where the environmental temperature is significantly different from the assumed temperature.

Means for Solving the Problem

[0008] In one aspect of the present invention, a control device for a light source including a wavelength-variable filter includes temperature receiving means for receiving substrate temperature information which is information indicating the temperature of a substrate on which the light source is provided, and housing temperature information which is information indicating the temperature of a housing that houses the substrate, and control means for controlling the substrate temperature and the refractive index of the wavelength-variable filter based on the substrate temperature information and the housing temperature information so that the frequency of transmission light output from the light source becomes a desired frequency.

[0009] Also, in another aspect of the present invention, a control method for a light source including a wavelength-variable filter receives substrate temperature information which is information indicating the temperature of a substrate on which the light source is provided, and housing temperature information which is information indicating the temperature of a housing that houses the substrate, and controls the substrate temperature and the refractive index of the wavelength-variable filter based on the substrate temperature information and the housing temperature information so that the frequency of transmission light output from the light source becomes a desired frequency.

Effects of the Invention

[0010] According to the present invention, it becomes possible to oscillate transmission light at an arbitrary oscillation frequency even in an environment where the environmental temperature is significantly different from the assumed temperature.

Brief Description of the Drawings

[0011]

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Embodiments for Carrying Out the Invention

[0012] [First Embodiment] The first embodiment of the present invention will be described. A specific example of the control device 10 in the first embodiment is the control device 20 in the second embodiment and the control device 30 in the third embodiment described later.

[0013] FIG. 1 shows a configuration example of the control device 10 of the present embodiment. The control device 10 of the present embodiment includes a temperature receiving unit 11 (temperature receiving means) and a control unit 12 (control means).

[0014] The control device 10 is a control device for a light source. The light source includes a wavelength-variable filter.

[0015] The temperature receiving unit 11 receives substrate temperature information which is information indicating the substrate temperature and housing temperature information which is information indicating the housing temperature. The substrate temperature is the temperature of the substrate on which the light source is provided. The housing temperature is the temperature of the housing that houses the substrate. The housing temperature is, for example, the temperature inside the housing or the surface temperature of the inner surface of the housing. The control unit 12 controls the substrate temperature and the refractive index of the wavelength-variable filter based on the substrate temperature information and the housing temperature information so that the frequency of the transmitted light output by the light source becomes a desired frequency.

[0016] Next, FIG. 2 shows an example of the operation flow of the control device 10 of the present embodiment.

[0017] The temperature receiving unit 11 receives the substrate temperature information and the housing temperature information (step S101). The control unit 12 controls the substrate temperature and the refractive index of the wavelength-variable filter based on the substrate temperature information and the housing temperature information so that the frequency of the transmitted light output by the light source becomes a desired frequency (step S102).

[0018] As described above, in the first embodiment of the present invention, the control device 10 includes a temperature receiving unit 11 and a control unit 12. The temperature receiving unit 11 receives substrate temperature information which is information indicating the substrate temperature that is the temperature of the substrate on which the light source is provided and housing temperature information which is information indicating the housing temperature that is the temperature of the housing that houses the substrate. The control unit 12 controls the substrate temperature and the refractive index of the wavelength-variable filter based on the substrate temperature information and the housing temperature information so that the frequency of the transmitted light output by the light source becomes a desired frequency. By controlling the substrate temperature and the refractive index of the wavelength-variable filter, the refractive index of the waveguide and the wavelength-variable filter changes, so the frequency of the transmitted light can be adjusted. Therefore, even in an environment where the environmental temperature is significantly different from the assumed temperature, it is possible to oscillate the transmitted light at an arbitrary oscillation frequency.

[0019] [Second Embodiment] Next, a second embodiment of the present invention will be described.

[0020] First, FIG. 3 shows a configuration example of the optical transceiver 60 according to the present embodiment. The optical transceiver 60 includes an optical receiver 61 and an optical transmission module 62. The optical receiver 61 receives an optical signal from outside the optical transceiver 60. The optical transmission module 62 outputs the transmission light after being modulated by a modulator 63 described later. The optical receiver 61 and the optical transmission module 62 operate independently.

[0021] Next, FIG. 4 shows a configuration example of the optical transmission module 62 of the present embodiment. The optical transmission module 62 includes a modulator 63 and a light source device 40. The light source device 40 outputs the transmission light. The modulator 63 modulates and outputs the transmission light output from the light source device 40.

[0022] Next, FIG. 5 shows a configuration example of the light source device 40 of the present embodiment. The light source device 40 includes a control device 20, a light source 41, a substrate temperature measurement unit 42 (substrate temperature measurement means), a housing temperature measurement unit 43 (housing temperature measurement means), a substrate temperature control unit 44 (substrate temperature control means), and a filter heating unit 45 (filter heating means). The light source 41 outputs the transmission light. The functions of the control device 20, the substrate temperature measurement unit 42, the housing temperature measurement unit 43, the substrate temperature control unit 44, and the filter heating unit 45 will be described later.

[0023] Next, FIG. 6 shows a configuration example of the light source 41. The light source 41 includes an SOA (Semiconductor Optical Amplifier) 411, a first wavelength variable filter 412, a second wavelength variable filter 413, a phase adjuster 414, and a partial reflection mirror 415. The light source 41 is provided on a substrate 100.

[0024] SOA411 is a compound semiconductor. A current is input into SOA411. And in SOA411, electricity is converted into light. An external resonator is constituted by the strong reflection surface of SOA411 and the partial reflection mirror 415. The periodic multiple transmission peaks due to this external resonator are the external resonator modes. The light generated in SOA411 reaches the partial reflection mirror 415 via the first wavelength variable filter 412, the second wavelength variable filter 413, and the phase adjuster 414. The light reflected by the partial reflection mirror 415 returns to SOA411 via the phase adjuster 414, the second wavelength variable filter 413, and the first wavelength variable filter 412, and is reflected by the strong reflection surface of SOA411. By repeating the reflection, among the multiple external resonator modes, the light of the set frequency is selected by the first wavelength variable filter 412 and the second wavelength variable filter 413, and the light source 41 oscillates in the selected mode. Note that the oscillation frequency set here is, for example, in the range of 191 to 196 THz.

[0025] In the partial reflection mirror 415, a part of the light is output as transmission light to the modulator 63. The phase adjuster 414 changes the effective resonator length in the external resonator constituted by the strong reflection surface of SOA411 and the partial reflection mirror 415 by changing the refractive index of the waveguide part of the phase adjuster 414. Thereby, the mode interval (FSR (Free Spectral Range)) of the external resonator changes, and accordingly, the frequency of the transmission light output from the light source 41 (partial reflection mirror 415) also changes.

[0026] Note that the first wavelength variable filter 412 and the second wavelength variable filter 413 change in refractive index due to a change in temperature, and the interval between the transmission peak wavelengths due to resonance changes. Thereby, the peak wavelengths passing through the first wavelength variable filter 412 and the second wavelength variable filter 413 also change.

[0027] Next, with reference to FIGS. 5 and 6, the substrate temperature measurement unit 42, the housing temperature measurement unit 43, the substrate temperature control unit 44, and the filter heating unit 45 of the light source device 40 will be described.

[0028] The substrate temperature measurement unit 42 measures the temperature of the substrate. A light source 41 is provided on the substrate. Hereinafter, the temperature of the substrate provided with the light source 41 is referred to as the substrate temperature. More specifically, the substrate temperature measurement unit 42 is provided on the substrate. The substrate temperature is the temperature at the position on the substrate where the substrate temperature measurement unit 42 is installed.

[0029] In addition, the housing temperature measurement unit 43 measures the temperature of the housing that houses the substrate. The housing temperature is, for example, the temperature inside the housing or the surface temperature of the inner surface of the housing. Hereinafter, the temperature of the housing of the optical transceiver 60 is referred to as the housing temperature. More specifically, the housing temperature measurement unit 43 is provided inside the housing. The housing temperature is the temperature at the position inside the housing where the housing temperature measurement unit 43 is installed. Also, since the light source 41 is provided on the substrate, the housing that houses the substrate is also the housing of the light source 41. The substrate temperature measurement unit 42 and the housing temperature measurement unit 43 are, for example, thermistors.

[0030] The substrate temperature control unit 44 and the filter heating unit 45 are provided on the substrate provided with the light source 41.

[0031] The substrate temperature control unit 44 controls the substrate temperature by heating or cooling the substrate. Also, the filter heating unit 45 controls the temperature of the wavelength-variable filter included in the light source 41. The filter heating unit 45 may control the temperature of both the first wavelength-variable filter 412 and the second wavelength-variable filter 413 or the temperature of one of them. In the present embodiment, for the sake of simplicity of control, the filter heating unit 45 is assumed to control the temperature of the first wavelength-variable filter 412. The substrate temperature control unit 44 and the filter heating unit 45 are, for example, heating elements. Note that hereinafter, the temperature of the wavelength-variable filter is referred to as the filter temperature. In the case of the present embodiment, the filter temperature is the temperature of the first wavelength-variable filter 412.

[0032] Next, with reference to FIG. 7, a configuration example of the control device 20 of the present embodiment will be described. The control device 20 includes a temperature reception unit 21 and a control unit 22.

[0033] The temperature receiving unit 21 receives substrate temperature information, which is information indicating the substrate temperature, from the substrate temperature measuring unit 42. Further, the temperature receiving unit 21 receives housing temperature information, which is information indicating the housing temperature, from the housing temperature measuring unit 43. For example, the temperature receiving unit 21 grasps the substrate temperature information based on the resistance value of a thermistor in contact with the substrate. Also, the temperature receiving unit 21 grasps the housing temperature information based on the resistance value of a thermistor installed in the housing.

[0034] Based on the substrate temperature information and the housing temperature information, the control unit 22 controls the substrate temperature and the refractive index of the wavelength variable filter so that the frequency of the transmitted light output by the light source 41 becomes a desired frequency even when the housing temperature changes, with respect to the temperature unevenness on the substrate accompanying the change in the housing temperature.

[0035] Before shipment, the light source 41 is adjusted so that it can oscillate at a desired frequency even if the refractive index of the first wavelength variable filter 412, the second wavelength variable filter 413, or the refractive index of the waveguide portion of the phase modulator 414 fluctuates somewhat at a reference housing temperature. Also, the control unit 22 controls the substrate temperature so that the substrate temperature becomes constant.

[0036] However, as described above, even if the control is performed so that the substrate temperature becomes constant, when the housing temperature changes due to a change in the ambient temperature, the transmitted light may oscillate outside the desired frequency range. When the housing temperature changes from the reference temperature, the control unit 22 of the present embodiment controls the substrate temperature and the refractive index of the wavelength variable filter so that the frequency of the transmitted light output by the light source 41 becomes a desired frequency. Hereinafter, controlling the substrate temperature and the refractive index of the wavelength variable filter so that the frequency of the transmitted light output by the light source 41 becomes a desired frequency may be referred to as frequency correction.

[0037] The control unit 22 of the present embodiment controls the substrate temperature by controlling the substrate temperature control unit 44 of the light source device 40. Further, the control unit 22 controls the refractive index of the wavelength-variable filter included in the light source 41 by controlling the filter heating unit 45 of the light source device 40. Note that the control device 20 of the present embodiment controls the refractive index of the wavelength-variable filter by controlling the filter heating unit 45, but a method other than temperature control may be used to control the refractive index of the wavelength-variable filter. Further, the control unit 22 controls the refractive index of any one of the two or more wavelength-variable filters included in the light source 41. The control unit 22 may control the refractive indices of any two or more of the two or more wavelength-variable filters included in the light source 41.

[0038] FIG. 8 shows an example of the phase-wavelength characteristics in the light source 41 with respect to the frequency correction based on the substrate temperature. The horizontal axis of the graph is the power (referred to as phase power) applied to the phase adjuster 414. The vertical axis of the graph is the wavelength of the transmitted light output from the light source 41. The light source 41 can change the wavelength of the transmitted light by changing the phase power applied to the phase adjuster 414. The relationship between the phase power and the wavelength of the transmitted light is referred to as the phase-wavelength characteristics. “Tcase” indicates the housing temperature.

[0039] The broken line is the phase-wavelength characteristics when the housing temperature is 35.6 degrees, and is also the desired phase-wavelength characteristics. In the case of this example, the reference temperature (or assumed temperature) assumed as the housing temperature at which the desired phase-wavelength characteristics can be obtained is 35.6 degrees. The solid line is the phase-wavelength characteristics before the control unit 22 performs frequency correction based on the substrate temperature. At this time, the housing temperature is 52 degrees. Due to the change in the housing temperature, the phase-wavelength characteristics are shifted downward to the left from the desired phase-wavelength characteristics. The thick line is the phase-wavelength characteristics after the control unit 22 performs frequency correction based on the substrate temperature and before performing frequency correction based on the filter temperature. By the control unit 22 performing frequency correction based on the substrate temperature, the phase-wavelength characteristics are approaching the desired wavelength characteristics.

[0040] Fig. 9 shows an example of the phase wavelength characteristics of the light source 41 with respect to frequency correction based on the filter temperature. The horizontal axis and the vertical axis of the graph are the same as those in Fig. 8. "Tcase" indicates the housing temperature. The dashed line represents the phase wavelength characteristics when the housing temperature is 35.6 degrees, which is also the desired phase wavelength characteristics. The solid line represents the phase wavelength characteristics before performing frequency correction based on the filter temperature after the control unit 22 performs frequency correction based on the substrate temperature. The thick line represents the phase wavelength characteristics after the control unit 22 performs frequency correction based on the filter temperature.

[0041] By controlling the filter temperature by the control unit 22, the phase wavelength characteristics shift to the upper right of the graph, and the phase wavelength characteristics approach the desired characteristics. In this way, by controlling the filter temperature in addition to the substrate temperature, the phase wavelength characteristics can be made closer to the desired phase wavelength characteristics. Thereby, the control device 20 can make the frequency of the transmitted light output by the light source 41 become the desired frequency.

[0042] Also, in the present embodiment, the control device 20 corrects the frequency deviation (the vertical deviation in the graphs of Figs. 8 and 9) based on the substrate temperature and further controls the filter temperature. By correcting the frequency deviation by correcting the substrate temperature, the change amount of the filter temperature can be minimized. If the frequency deviation is corrected only by the filter temperature, the influence due to internal reflection changes, and in some cases, the oscillation frequency becomes unstable. However, in the present embodiment, since the change amount of the filter temperature can be made small, the destabilization of the oscillation frequency can be suppressed. Also, by using one wavelength-variable filter for temperature control, the temperature control can be simplified.

[0043] Also, the control unit 22 may control the substrate temperature control unit 44 and the filter heating unit 45 so that the frequency of the transmitted light becomes the desired frequency based on the relationship between the substrate temperature and the power value with respect to the housing temperature. This power value is the power value consumed by the substrate temperature control unit 44 and the power value consumed by the filter heating unit 45.

[0044] The light source device 40 may include a storage unit (memory) (not shown) that stores a look-up table (LUT) that stores the relationship between the substrate temperature and the housing temperature and the power values. Note that the look-up table (LUT) may store the output voltage in correspondence with the substrate temperature and the housing temperature. The output voltage is the output voltage to the substrate temperature control unit 44 and the output voltage to the filter heating unit 45. Here, the control unit 22 is typically a micro controller unit (MCU).

[0045] More specifically, for example, before the optical transceiver 60 is shipped, the adjuster performs the following operations to store the look-up table in the light source device 40.

[0046] For example, the adjuster controls the control device 20 using a test terminal. In the test mode, the control device 20 controls the substrate temperature control unit 44 and the filter heating unit 45 according to an instruction from the test terminal. Also, in the test mode, the control device 20 outputs the substrate temperature information and the housing temperature information to the test terminal. Further, the adjuster measures the phase wavelength characteristics of the transmitted light of the optical transceiver 60 using a measuring instrument.

[0047] First, the adjuster changes the housing temperature of the optical transceiver 60 from the reference temperature by changing the environmental temperature. Then, the adjuster controls the substrate temperature control unit 44 from the test terminal so that the phase wavelength characteristics can approach the desired phase wavelength characteristics. Also, the adjuster controls the filter heating unit 45 from the test terminal so that the phase wavelength characteristics can approach the desired phase wavelength characteristics, and further so that the optical output is maximized. Then, the adjuster stores, in the storage unit of the light source device 40 as a look-up table, the values of the power values (or output voltages) of the substrate temperature control unit 44 and the filter heating unit 45 that enabled the phase wavelength characteristics to approach the desired phase wavelength characteristics, in association with the substrate temperature and the housing temperature.

[0048] Next, an example of the operation flow of the control device 20 of the present embodiment will be described with reference to FIG. 2.

[0049] The temperature receiving unit 21 receives the substrate temperature information from the substrate temperature measuring unit 42. Further, the temperature receiving unit 21 receives the housing temperature information from the housing temperature measuring unit 43 (step S101).

[0050] Based on the substrate temperature information and the housing temperature information, the control unit 22 controls the substrate temperature and the filter temperature so that the frequency of the transmitted light output by the light source 41 becomes a desired frequency (step S102). Note that the control unit 22 may control either the substrate temperature or the filter temperature first, or may control the substrate temperature and the filter temperature simultaneously.

[0051] As described above, in the second embodiment of the present invention, the control device 20 includes a temperature receiving unit 21 and a control unit 22. The temperature receiving unit 21 receives substrate temperature information, which is information indicating the substrate temperature that is the temperature of the substrate on which the light source is provided, and housing temperature information, which is information indicating the housing temperature that is the temperature of the housing that houses the substrate. Based on the substrate temperature information and the housing temperature information, the control unit 22 controls the substrate temperature and the refractive index of the wavelength-variable filter so that the frequency of the transmitted light output by the light source becomes a desired frequency. By controlling the substrate temperature and the refractive index of the wavelength-variable filter, the refractive index of the waveguide and the wavelength-variable filter changes, so that the frequency of the transmitted light can be adjusted. Therefore, even in an environment where the ambient temperature is significantly different from the assumed temperature, it is possible to oscillate the transmitted light at an arbitrary oscillation frequency.

[0052] Further, the control unit 22 of the control device 20 of the present embodiment controls the refractive index of any one of the two or more wavelength-variable filters included in the light source 41. Thereby, the control of the refractive index of the wavelength-variable filter can be simplified.

[0053] Further, the substrate is provided with a substrate temperature control unit 44 that changes the substrate temperature and a filter heating unit 45 that changes the temperature of the wavelength-variable filter. Further, the control unit 22 controls the substrate temperature by controlling the substrate temperature control unit 44 and controls the refractive index of the wavelength-variable filter by controlling the filter heating unit 45. Thereby, control of the substrate temperature and control of the refractive index of the wavelength-variable filter can be easily realized.

[0054] Further, the control unit 22 controls the substrate temperature and the refractive index of the wavelength-variable filter so that the frequency becomes a desired frequency based on the relationship between the power values consumed by the substrate temperature control unit 44 and the filter heating unit 45 with respect to the substrate temperature and the housing temperature. Thereby, control of the substrate temperature and control of the refractive index of the wavelength-variable filter can be easily realized.

[0055] [Third Embodiment] Next, a third embodiment of the present invention will be described. In this embodiment, a case where the optical transceiver further has a frequency detection function will be described.

[0056] First, FIG. 10 shows a configuration example of an optical transceiver 70 according to this embodiment. The optical transceiver 70 includes an optical receiver 61 and an optical transmission module 72. The optical receiver 61 receives light. The optical transmission module 72 outputs modulated transmission light.

[0057] Next, FIG. 11 shows a configuration example of the optical transmission module 72 of this embodiment. The optical transmission module 72 includes a modulator 63 and a light source device 50. The light source device 50 outputs transmission light. The modulator 63 modulates and outputs the transmission light output from the light source device 50.

[0058] Next, FIG. 12 shows a configuration example of the light source device 50 of the present embodiment. The light source device 50 includes a control device 30, a light source 41, a substrate temperature measurement unit 42, a housing temperature measurement unit 43, a substrate temperature control unit 44, and a filter heating unit 45. Further, the light source device 50 further includes a frequency detection unit 56 (frequency detection means) and a frequency detection filter heating unit 58 (frequency detection filter heating means). Since the light source 41, the substrate temperature measurement unit 42, the housing temperature measurement unit 43, the substrate temperature control unit 44, and the filter heating unit 45 are the same as those in the second embodiment, the description thereof is omitted. The control device 30 will be described later.

[0059] The frequency detection unit 56 detects the frequency of the transmitted light output from the partial reflection mirror 415. Then, the frequency detection unit 56 outputs the information on the detected frequency to the control device 30. In the present embodiment, the frequency detection unit 56 detects the frequency of the transmitted light using the wavelength-variable filter 57 for frequency detection. The wavelength-variable filter 57 for frequency detection is provided on the substrate on which the light source 41 is provided.

[0060] For example, the frequency detection unit 56 can detect the frequency of the transmitted light based on the ratio of the intensity of the light output from the wavelength-variable filter 57 for frequency detection (PD2) to the intensity of the light input to the wavelength-variable filter 57 for frequency detection (PD1) and the transmission characteristic of the wavelength-variable filter 57 for frequency detection. Hereinafter, the ratio of PD2 to PD1 is referred to as the input-output ratio. The transmission characteristic is the characteristic of the relationship between the frequency of the transmitted light and the input-output ratio. Specifically, the frequency detection unit 56 measures PD1 and PD2 and calculates the input-output ratio. Then, the frequency detection unit 56 refers to the information on the transmission characteristic of the wavelength-variable filter 57 for frequency detection at the reference temperature and detects the frequency corresponding to the input-output ratio as the frequency of the transmitted light. In this way, the frequency detection unit 56 can detect the frequency of the transmitted light. Note that the information on the transmission characteristic of the wavelength-variable filter 57 for frequency detection when the housing temperature is the reference temperature is stored in a storage unit (not shown).

[0061] The filter heating unit 58 for frequency detection controls the temperature of the wavelength-variable filter 57 for frequency detection. The filter heating unit 58 for frequency detection is, for example, a heating element. The filter heating unit 58 for frequency detection is provided on the substrate on which the light source 41 is provided. Hereinafter, the temperature of the filter heating unit 58 for frequency detection will be referred to as the filter temperature for frequency detection.

[0062] Next, FIG. 13 shows a configuration example of the control device 30 of the present embodiment. The control device 30 includes a temperature reception unit 21 and a control unit 32.

[0063] The temperature reception unit 21 receives substrate temperature information, which is information indicating the substrate temperature, from the substrate temperature measurement unit 42. The temperature reception unit 21 also receives housing temperature information, which is information indicating the housing temperature, from the housing temperature measurement unit 43.

[0064] Similar to the second embodiment, the control unit 32 controls (frequency correction) the substrate temperature and the refractive index of the wavelength-variable filter so that the frequency of the transmission light output from the light source 41 becomes a desired frequency based on the substrate temperature information and the housing temperature information.

[0065] In addition, the control unit 32 outputs the frequency information detected by the frequency detection unit 56 to an external monitor (not shown) or the like.

[0066] In addition, the control unit 32 further controls the refractive index of the wavelength-variable filter 57 for frequency detection based on the housing temperature so that the frequency detected by the frequency detection unit 56 is correct.

[0067] Due to the positions of the substrate temperature control unit 44 and the filter heating unit 45 and the shape of the housing, there are temperature non-uniformities on the substrate. Furthermore, when frequency correction based on the substrate temperature is performed by the control unit 32, non-uniformities also occur in the amount of temperature change due to the frequency correction. Due to these non-uniformities in the amount of temperature change, the temperatures of the first wavelength-variable filter 412 and the wavelength-variable filter 57 for frequency detection change with different amounts of change from each other. Therefore, a difference occurs between the frequency of the transmitted light output from the light source 41 and the frequency detected by the frequency detection unit 56. Thus, the control unit 32 of the present embodiment controls the refractive index of the wavelength-variable filter 57 for frequency detection so that the frequency detected by the frequency detection unit 56 becomes correct.

[0068] A specific method for controlling the refractive index of the wavelength-variable filter 57 for frequency detection will be described.

[0069] Figures 14 to 16 show examples of the transmission characteristics of the wavelength-variable filter 57 for frequency detection regarding the control of the filter temperature for frequency detection. The horizontal axis of the graph indicates the difference between the frequency of the transmitted light and the reference frequency. The reference frequency may be an arbitrary frequency or a desired frequency. Here, it will be described assuming that the reference frequency is an arbitrary frequency. Also, the vertical axis of the graph indicates the ratio of PD2 to PD1 (input / output ratio).

[0070] Figure 14 is an example of the transmission characteristics of the wavelength-variable filter 57 for frequency detection when the housing temperature is the reference temperature. The frequency detection unit 56 detects the frequency of the transmitted light based on the information of this transmission characteristic.

[0071] Figure 15 is an example of the transmission characteristics of the wavelength-variable filter 57 for frequency detection when the housing temperature changes from the reference temperature. This is the transmission characteristic before the frequency correction described in the second embodiment. In Figure 15, as indicated by the solid line arrow, the transmission characteristic has shifted to the right. Also, the dashed line arrow indicates the amount of shift of the transmission characteristic of the first wavelength-variable filter 412 in this case. Thus, the amount of shift of the transmission characteristic is different between the wavelength-variable filter 57 for frequency detection and the first wavelength-variable filter 412.

[0072] FIG. 16 shows an example of the transmission characteristics of the wavelength variable filter 57 for frequency detection after frequency correction. The transmission characteristics of the first wavelength variable filter 412 return to the position of the transmission characteristics when the housing temperature is the reference temperature by frequency correction. However, the transmission characteristics of the wavelength variable filter 57 for frequency detection shift to the left from the state of FIG. 14 due to the change in the housing temperature by frequency correction. In this state, the frequency detection unit 56 cannot correctly detect the frequency of the transmitted light. Therefore, the control unit 32 of the present embodiment returns the transmission characteristics of the wavelength variable filter 57 for frequency detection to the state of FIG. 14 by controlling the refractive index of the wavelength variable filter 57 for frequency detection.

[0073] The control unit 32 controls the refractive index of the wavelength variable filter 57 for frequency detection, for example, by controlling the frequency detection filter heating unit 58 to control the frequency detection filter temperature. Note that the control unit 32 may control the refractive index of the wavelength variable filter 57 for frequency detection by a method other than temperature control.

[0074] The light source device 50 may include, for example, a storage unit (not shown) that stores a look-up table showing the relationship between the housing temperature and the power value consumed by the frequency detection filter heating unit 58. Alternatively, the look-up table may show the relationship between the housing temperature and the output voltage to the frequency detection filter heating unit 58. Then, the control unit 32 controls the frequency detection filter heating unit 58 based on the housing temperature with reference to the look-up table.

[0075] More specifically, for example, the adjuster performs the following operations, such as before the shipment of the optical transceiver 60, and stores the look-up table in the storage unit of the light source device 50.

[0076] For example, the adjuster controls the control device 30 using a test terminal. In the test mode, the control device 30 controls the frequency detection filter heating unit 58 according to an instruction from the test terminal. Further, the control device 30 performs the frequency correction described in the second embodiment. By the frequency correction, the frequency of the transmitted light remains unchanged even when the housing temperature changes. Also, in the test mode, the control device 30 outputs the housing temperature information and the information indicating the ratio (input / output ratio) of PD2 to PD1 to the test terminal.

[0077] First, the adjuster changes the housing temperature from the reference temperature by changing the environmental temperature. Then, the adjuster controls the frequency detection filter heating unit 58 from the test terminal so that the transmission characteristic of the wavelength variable filter 57 for frequency detection becomes the same as the transmission characteristic when the housing temperature is the reference temperature. Then, the adjuster associates the power value (or output voltage) to the frequency detection filter heating unit 58 when the transmission characteristic becomes the same as the transmission characteristic at the reference temperature with the housing temperature and stores it in the storage unit of the light source device 50 as a look-up table.

[0078] So far, the method of controlling the refractive index of the wavelength variable filter 57 for frequency detection so that the frequency detected by the frequency detection unit 56 is correct has been described. However, instead of controlling the refractive index of the wavelength variable filter 57 for frequency detection, the control unit 32 may calculate the correct frequency and output the information of the correct frequency to an external monitor or the like. Hereinafter, the method of calculating the correct frequency will be described.

[0079] The control unit 32 receives the frequency information detected by the frequency detection unit 56 from the frequency detection unit 56. Then, based on the housing temperature and the frequency detected by the frequency detection unit 56, the correct frequency is calculated.

[0080] In the case of this method, the light source device 50 may not include the frequency detection filter heating unit 58.

[0081] The light source device 50 may include, for example, a storage unit (not shown) that stores a look-up table indicating the relationship between the housing temperature and the addition value. The addition value is an addition value for the frequency detected by the frequency detection unit 56. The addition value may be a negative value. Then, the control unit 32 refers to the look-up table and adds the addition value associated with the housing temperature to the frequency detected by the frequency detection unit 56 to calculate the correct frequency.

[0082] More specifically, for example, the adjuster performs the following operations before the shipment of the optical transceiver 60, etc., and stores the look-up table in the storage unit of the light source device 50.

[0083] For example, the adjuster uses a test terminal. In the test mode, the control device 30 performs the frequency correction described in the second embodiment. By the frequency correction, the frequency of the transmitted light remains unchanged even when the housing temperature changes. Also, in the test mode, the control device 30 outputs the housing temperature information and the information indicating the frequency (or frequencies) detected by the frequency detection unit 56 to the test terminal.

[0084] First, the adjuster changes the housing temperature from the reference temperature by changing the environmental temperature. Then, the adjuster associates the value obtained by subtracting the frequency detected by the frequency detection unit 56 from the correct frequency with the housing temperature, and stores it in the storage unit of the light source device 50 as a look-up table.

[0085] Also, when the frequency detected by the frequency detection unit 56 is different from the desired frequency (set frequency), in addition to the frequency correction described in the second embodiment, the control unit 32 may further perform control to increase or decrease the substrate temperature so that the detected frequency becomes the desired frequency.

[0086] Next, an example of the operation flow of the control device 30 of the present embodiment will be described with reference to FIG. 17.

[0087] The temperature receiving unit 21 receives substrate temperature information, which is information indicating the substrate temperature, from the substrate temperature measuring unit 42. Further, the temperature receiving unit 21 receives housing temperature information, which is information indicating the housing temperature, from the housing temperature measuring unit 43 (step S201).

[0088] Based on the substrate temperature information and the housing temperature information, the control unit 32 controls the substrate temperature and the refractive index of the wavelength-variable filter so that the frequency of the transmitted light output by the light source 41 becomes a desired frequency (step S202).

[0089] Further, the control unit 32 controls the refractive index of the wavelength-variable filter 57 for frequency detection so that the frequency detected by the frequency detection unit 56 becomes correct based on the housing temperature information (step S203). Alternatively, the control unit 32 calculates the correct frequency based on the housing temperature information.

[0090] As described above, in the third embodiment of the present invention, the control device 30 includes the temperature receiving unit 21 and the control unit 32. The temperature receiving unit 21 receives substrate temperature information, which is information indicating the substrate temperature that is the temperature of the substrate provided with the light source, and housing temperature information, which is information indicating the housing temperature that is the temperature of the housing that houses the substrate. Based on the substrate temperature information and the housing temperature information, the control unit 32 controls the substrate temperature and the refractive index of the wavelength-variable filter so that the frequency of the transmitted light output by the light source becomes a desired frequency. By controlling the substrate temperature and the refractive index of the wavelength-variable filter, the refractive index of the waveguide and the wavelength-variable filter changes, so that the frequency of the transmitted light can be adjusted. Therefore, even in an environment where the environmental temperature is significantly different from the assumed temperature, it is possible to oscillate the transmitted light at an arbitrary oscillation frequency.

[0091] In addition, in the present embodiment, a wavelength-variable filter for frequency detection 57, which is a wavelength-variable filter for detecting the frequency of transmitted light, is further provided on the substrate. Further, the control unit 32 controls the refractive index of the wavelength-variable filter for frequency detection 57 based on the housing temperature so that the frequency detected by the frequency detection is correct. By controlling the refractive index of the wavelength-variable filter for frequency detection 57, the transmission characteristics of the wavelength-variable filter for frequency detection 57 can be adjusted to the transmission characteristics when the housing temperature is the reference temperature (the transmission characteristics used for frequency detection). Therefore, the frequency detected by the frequency detection can be made correct.

[0092] In addition, in the present embodiment, a filter heating unit 58 for frequency detection for controlling the temperature of the wavelength-variable filter for frequency detection 57 is further provided on the substrate. Further, the control unit 32 controls the refractive index of the wavelength-variable filter for frequency detection 57 by controlling the filter heating unit 58 for frequency detection. Therefore, the control of the refractive index of the wavelength-variable filter for frequency detection 57 can be easily realized.

[0093] In addition, the control unit 32 of the present embodiment controls the filter heating unit 58 for frequency detection based on the relationship between the housing temperature and the power value consumed by the filter heating unit 58 for frequency detection. Therefore, the control of the refractive index of the wavelength-variable filter for frequency detection 57 can be easily realized.

[0094] In addition, in the present embodiment, a wavelength-variable filter for frequency detection 57, which is a wavelength-variable filter for detecting the frequency of transmitted light, is further provided on the substrate. Further, the control unit 32 calculates and outputs the correct frequency from the housing temperature and the frequency detected by the frequency detection. Therefore, as a result of the frequency detection, the correct frequency can be output.

[0095] In addition, the control unit 32 of the present embodiment calculates the correct frequency based on the relationship between the housing temperature and the added value to the frequency detected by the frequency detection. Therefore, the calculation of the correct frequency can be easily realized.

[0096] Some or all of the above embodiments may be described as follows in the appended claims, but are not limited thereto.

[0097] (Appendix 1) A control device for a light source including a wavelength-variable filter, temperature receiving means for receiving substrate temperature information which is information indicating the temperature of the substrate on which the light source is provided, and housing temperature information which is information indicating the temperature of the housing that houses the substrate; control means for controlling the substrate temperature and the refractive index of the wavelength-variable filter so that the frequency of the transmitted light output by the light source becomes a desired frequency based on the substrate temperature information and the housing temperature information. A control device comprising:

[0098] (Appendix 2) The control means controls the refractive index of any one of the two or more wavelength-variable filters included in the light source. The control device according to Appendix 1.

[0099] (Appendix 3) The substrate is provided with substrate temperature control means for changing the substrate temperature and filter heating means for changing the temperature of the wavelength-variable filter. The control means controls the substrate temperature by controlling the substrate temperature control means, and controls the refractive index of the wavelength-variable filter by controlling the filter heating means. The control device according to Appendix 1 or Appendix 2.

[0100] (Appendix 4) The control means controls the substrate temperature and the refractive index of the wavelength-variable filter so that the frequency of the transmitted light becomes a desired frequency based on the relationship between the substrate temperature and the housing temperature and the power values consumed by the substrate temperature control means and the filter heating means. The control device according to Appendix 3.

[0101] (Appendix 5) The substrate is further provided with a wavelength-variable filter for frequency detection for detecting the frequency of the transmitted light. The control means further controls the refractive index of the wavelength-variable filter for frequency detection based on the housing temperature so that the frequency detected by the frequency detection is correct. The control device according to any one of Appendices 1 to 4.

[0102] (Appendix 6) The substrate is further provided with filter heating means for frequency detection for controlling the temperature of the wavelength-variable filter for frequency detection. The control means controls the refractive index of the wavelength-variable filter for frequency detection by controlling the filter heating means for frequency detection. The control device according to Appendix 5.

[0103] (Appendix 7) The control means controls the filter heating means for frequency detection from the relationship between the housing temperature and the power value consumed by the filter heating means for frequency detection. The control device according to Appendix 6.

[0104] (Appendix 8) The substrate is further provided with a wavelength-variable filter for frequency detection for detecting the frequency of the transmitted light. The control means further calculates and outputs a correct frequency from the housing temperature and the frequency detected by the frequency detection. The control device according to any one of Appendices 1 to 4.

[0105] (Appendix 9) The control means calculates a correct frequency from the relationship between the housing temperature and the added value to the frequency detected by the frequency detection. The control device according to Appendix 8.

[0106] (Appendix 10) The control device according to any one of Appendices 1 to 9, and the light source.

[0107] (Appendix 11) The light source device described in Appendix 10, and a modulator for modulating the transmitted light A light transmission module comprising the same.

[0108] (Appendix 12) The light transmission module described in Appendix 11, and a photoreceiver for receiving an optical signal A photoreceiver comprising the same.

[0109] (Appendix 13) A method for controlling a light source including a wavelength variable filter, receiving substrate temperature information which is information indicating the substrate temperature which is the temperature of the substrate on which the light source is provided, and housing temperature information which is information indicating the housing temperature which is the temperature of the housing housing the substrate, and controlling the substrate temperature and the refractive index of the wavelength variable filter based on the substrate temperature information and the housing temperature information so that the frequency of the transmitted light output from the light source becomes a desired frequency. Control method.

[0110] (Appendix 14) Controlling the refractive index of any one of the plurality of wavelength variable filters included in the light source. The control method described in Appendix 13.

[0111] (Appendix 15) The substrate is provided with substrate temperature control means for changing the substrate temperature and filter heating means for changing the temperature of the wavelength variable filter, controlling the substrate temperature by controlling the substrate temperature control means, and controlling the refractive index of the wavelength variable filter by controlling the filter heating means. The control method described in Appendix 13 or Appendix 14.

[0112] (Appendix 16) Based on the relationship between the substrate temperature and the housing temperature and the power values consumed by the substrate temperature control means and the filter heating means, the substrate temperature and the refractive index of the wavelength-variable filter are controlled so that the frequency of the transmitted light becomes a desired frequency. The control method according to Supplementary Note 15.

[0113] (Supplementary Note 17) The substrate is further provided with a wavelength-variable filter for frequency detection for detecting the frequency of the transmitted light. Furthermore, based on the housing temperature, the refractive index of the wavelength-variable filter for frequency detection is controlled so that the frequency detected by the frequency detection is correct. The control method according to any one of Supplementary Notes 13 to 16.

[0114] (Supplementary Note 18) The substrate is further provided with filter heating means for frequency detection for controlling the temperature of the wavelength-variable filter for frequency detection. By controlling the filter heating means for frequency detection, the refractive index of the wavelength-variable filter for frequency detection is controlled. The control method according to Supplementary Note 17.

[0115] (Supplementary Note 19) Based on the relationship between the housing temperature and the power value consumed by the filter heating means for frequency detection, the filter heating means for frequency detection is controlled. The control method according to Supplementary Note 18.

[0116] (Supplementary Note 20) The substrate is further provided with a wavelength-variable filter for frequency detection for detecting the frequency of the transmitted light. Furthermore, a correct frequency is calculated and output from the housing temperature and the frequency detected by the frequency detection. The control method according to any one of Supplementary Notes 13 to 16.

[0117] (Supplementary Note 21) Calculate the correct frequency from the relationship between the cabinet temperature and the added value to the frequency detected by the frequency detection. The control method according to Supplementary Note 20.

[0118] As described above, the present invention has been described with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

Explanation of Signs

[0119] 10, 20, 30 Control device 11, 21 Temperature receiving unit 12, 22, 32 Control unit 40, 50 Light source device 41 Light source 42 Substrate temperature measurement unit 43 Cabinet temperature measurement unit 44 Substrate temperature control unit 45 Filter heating unit 56 Frequency detection unit 57 Wavelength-variable filter for frequency detection 60, 70 Optical transceiver

Claims

1. A control device for a light source including a wavelength-variable filter, comprising: temperature receiving means for receiving substrate temperature information, which is information indicating the temperature of a substrate on which the light source is provided, and housing temperature information, which is information indicating the temperature of a housing that houses the substrate; control means for controlling the substrate temperature and the refractive index of the wavelength-variable filter so that the frequency of transmission light output from the light source becomes a desired frequency based on the substrate temperature information and the housing temperature information; and a wavelength-variable filter for frequency detection for detecting the frequency of the transmission light is further provided on the substrate separately from the wavelength-variable filter included in the light source; the control means further controls the refractive index of the wavelength-variable filter for frequency detection based on the housing temperature so that the frequency detected by the frequency detection is correct. The control device.

2. The substrate further includes frequency detection filter heating means for controlling the temperature of the wavelength-variable filter for frequency detection, and the control means controls the refractive index of the wavelength-variable filter for frequency detection by controlling the frequency detection filter heating means. The control device according to claim 1.

3. A wavelength-variable filter for frequency detection for detecting the frequency of the transmission light is further provided on the substrate, and the control means further calculates and outputs a correct frequency from the housing temperature and the frequency detected by the frequency detection. The control device according to any one of claims 1 or 2.

4. A control device for a light source including a wavelength-variable filter, comprising: temperature receiving means for receiving substrate temperature information, which is information indicating the temperature of a substrate on which the light source is provided, and housing temperature information, which is information indicating the temperature of a housing that houses the substrate; Control means for controlling the substrate temperature and the refractive index of the wavelength-variable filter so that the frequency of the transmitted light output from the light source becomes a desired frequency based on the substrate temperature information and the housing temperature information. comprising On the substrate, a wavelength-variable filter for frequency detection for detecting the frequency of the transmitted light is further provided separately from the wavelength-variable filter included in the light source. The control means further calculates and outputs a correct frequency from the housing temperature and the frequency detected by the frequency detection. Control device.

5. The frequency detection is based on an input / output ratio, which is a ratio of the intensity of the light output from the wavelength-variable filter for frequency detection to the intensity of the light input to the wavelength-variable filter for frequency detection, and a transmission characteristic, which is a characteristic of the relationship between the frequency of the transmitted light and the input / output ratio in the wavelength-variable filter for frequency detection. The control device according to any one of claims 1 to 4.

6. Among the two or more wavelength-variable filters included in the light source, the control means controls the refractive index of any one of the wavelength-variable filters. The control device according to any one of claims 1 to 5.

7. On the substrate, substrate temperature control means for changing the substrate temperature and filter heating means for changing the temperature of the wavelength-variable filter are provided. The control means controls the substrate temperature by controlling the substrate temperature control means and controls the refractive index of the wavelength-variable filter by controlling the filter heating means. The control device according to any one of claims 1 to 6.

8. The control device according to any one of claims 1 to 7, and the light source Light source device comprising.

9. The light source device according to claim 8, and A modulator for modulating the transmitted light An optical transmission module comprising the same.

10. The optical transmission module according to claim 9, and An optical receiver for receiving an optical signal An optical transceiver comprising the same.

11. A method for controlling a light source including a wavelength variable filter, comprising: receiving substrate temperature information indicating the temperature of a substrate on which the light source is provided, and housing temperature information indicating the temperature of a housing accommodating the substrate; controlling the substrate temperature and the refractive index of the wavelength variable filter based on the substrate temperature information and the housing temperature information such that the frequency of transmitted light output from the light source becomes a desired frequency; further providing, separately from the wavelength variable filter included in the light source, a wavelength variable filter for frequency detection for detecting the frequency of the transmitted light on the substrate; controlling the refractive index of the wavelength variable filter for frequency detection based on the housing temperature so that the frequency detected by the frequency detection is correct; A control method.

12. A method for controlling a light source including a wavelength variable filter, comprising: receiving substrate temperature information indicating the temperature of a substrate on which the light source is provided, and housing temperature information indicating the temperature of a housing accommodating the substrate; controlling the substrate temperature and the refractive index of the wavelength variable filter based on the substrate temperature information and the housing temperature information such that the frequency of transmitted light output from the light source becomes a desired frequency; further providing, separately from the wavelength variable filter included in the light source, a wavelength variable filter for frequency detection for detecting the frequency of the transmitted light on the substrate; calculating and outputting a correct frequency from the housing temperature and the frequency detected by the frequency detection; A control method.

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