JP2020109800A - Semiconductor laser device - Google Patents

Abstract

To obtain a semiconductor laser device that can be easily adjusted and has a wider temperature range in which uncooled operation can be realized.SOLUTION: A semiconductor laser device includes a plurality of DFB lasers with different oscillation wavelengths, a combiner that combines the outputs of the plurality of DFB lasers, an EAM that modulates light output from the combiner, and a temperature detector that measures the temperature, and a laser selection controller that selects and switches a DFB laser to be operated from the plurality of DFB lasers on the basis of the temperature detected by the temperature detector.SELECTED DRAWING: Figure 1

Description

The present application relates to a semiconductor laser device.

In an access system which is an optical communication system between a relay station and a user, an electro-absorption modulator (EAM) suitable for high speed modulation and a distributed feedback semiconductor laser (DFB-LD) are provided. An EML (Electro-absorption Modulator integrated Laser), which is a semiconductor optical integrated device that integrates a semiconductor laser that outputs light of a single wavelength, such as a laser) is suitable.

In EML, it is necessary to use EAM having an appropriate light absorption characteristic for the wavelength of the semiconductor laser. On the other hand, both the wavelength characteristic of light absorption of EAM and the oscillation wavelength of the semiconductor laser have temperature dependence. Since the temperature dependence of the wavelength characteristics of the EAM is different from the temperature dependence of the oscillation wavelength of the semiconductor laser, when the temperature of the EML changes, not only the wavelength of the light but also the extinction ratio, which is the modulation characteristics of the EAM, changes. Can no longer be modulated. Therefore, in general, a configuration is used in which the PML is used to cool the EML to control the temperature.

The power required for cooling and controlling the temperature may occupy a large percentage of the power of the entire semiconductor laser device, and from the viewpoint of low power consumption, it is possible to operate without cooling, that is, in the so-called uncooled EML. Realization is desired. For example, Patent Document 1 proposes an uncooled operation by optimizing the difference between the laser oscillation wavelength λLD and the absorption peak wavelength λEA of EAM, Δλ=λLD−λEA, and adjusting the EAM bias voltage for each temperature. There is.

JP, 2007-279406, A

However, in the technique described in Patent Document 1, in order to suppress the fluctuation of the extinction ratio, it is necessary to adjust the EAM bias voltage according to the temperature, and the adjustment procedure is complicated. Moreover, the temperature range in which the uncooled operation can be realized was also limited.

The present application discloses a technique for solving the above-mentioned problems, and an object thereof is to obtain a semiconductor laser device which is easy to adjust and has a wider temperature range in which an uncooled operation can be realized.

A semiconductor laser device disclosed in the present application, a plurality of DFB lasers having different oscillation wavelengths, a multiplexer for coupling the outputs of the plurality of DFB lasers, an EAM for modulating the light output from the multiplexer, and a temperature It is provided with a temperature detector for measurement and a laser selection controller for selecting and switching a DFB laser to be operated among a plurality of DFB lasers based on the temperature detected by the temperature detector.

Also, a plurality of DFB lasers having different oscillation wavelengths, a multiplexer for coupling the outputs of the plurality of DFB lasers, an EAM for modulating the light output from the multiplexer, and a photocurrent for measuring the photocurrent of the EAM. A current detector and a laser selection controller for selecting and switching a DFB laser to be operated among a plurality of DFB lasers based on the value of the photocurrent detected by the photocurrent detector.

In addition, a DBR laser having an active region and a distributed reflection region, an EAM that modulates the light output from the DBR laser, a temperature detector that measures the temperature, and a distributed reflection based on the temperature detected by the temperature detector. And a DBR controller for controlling the injection current into the region.

Also, a DBR laser having an active region and a distributed reflection region, an EAM that modulates the light output from the DBR laser, a photocurrent detector that measures the photocurrent of the EAM, and a photocurrent detected by the photocurrent detector. And a DBR controller that controls the injection current into the distributed reflection region based on the value of.

According to the semiconductor laser device disclosed in the present application, it is possible to obtain a semiconductor laser device that is easy to adjust and has a wider temperature range in which uncooled operation can be realized.

1 is a block diagram showing a schematic configuration of a semiconductor laser device according to a first embodiment. FIG. 6 is a diagram for explaining the operation of the semiconductor laser device according to the first embodiment. FIG. 4 is a flowchart for explaining an algorithm of operation of the semiconductor laser device according to the first embodiment. FIG. 4 is a diagram for explaining the effect of the semiconductor laser device according to the first embodiment. 5 is a block diagram showing a schematic configuration of a semiconductor laser device according to a second embodiment. FIG. FIG. 9 is a diagram for explaining the operation of the semiconductor laser device according to the second embodiment. FIG. 7 is a flowchart for explaining an algorithm of operation of the semiconductor laser device according to the second embodiment. FIG. 9 is a block diagram showing a schematic configuration of a semiconductor laser device according to a third embodiment. FIG. 13 is a diagram showing an example of a look-up table of the semiconductor laser device according to the third embodiment. FIG. 11 is a flowchart for explaining an algorithm of the semiconductor laser device according to the third embodiment. FIG. 11 is a diagram for explaining the operation of the semiconductor laser device according to the third embodiment. FIG. 11 is a block diagram showing a schematic configuration of a semiconductor laser device according to a fourth embodiment. FIG. 13 is a diagram for explaining the operation of the semiconductor laser device according to the fourth embodiment. FIG. 16 is a flowchart for explaining an algorithm of operation of the semiconductor laser device according to the fourth embodiment. FIG. 13 is a block diagram showing another schematic configuration of the semiconductor laser device according to the fourth embodiment. FIG. 16 is a block diagram showing still another schematic configuration of the semiconductor laser device according to the fourth embodiment. FIG. 16 is a diagram showing an example of a look-up table of the semiconductor laser device according to the fourth embodiment.

Embodiment 1.
FIG. 1 is a schematic block diagram showing the configuration of the semiconductor laser device according to the first embodiment. The semiconductor laser device 100 includes three semiconductor lasers LD1, LD2, LD3 having different oscillation wavelengths, a multiplexer 104 for multiplexing their outputs, and one EAM (electroabsorption modulator) 105 mounted on the semiconductor optical device. An integrated device 10 is provided. Here, the semiconductor laser is a DFB laser (distributed feedback semiconductor laser). Further, a temperature detector 107 for detecting the temperature of the semiconductor optical integrated device 10 and a laser selection controller 106 for selecting and operating one of the three semiconductor lasers according to the detected temperature Tc of the temperature detector 107. I have it. In FIG. 1, three wavelength DFB lasers LD1, LD2, LD3, a multiplexer 104 and one EAM 105 are monolithically integrated as a semiconductor optical integrated device 10. As the multiplexer 104, for example, a multiplexer based on MMI (Multi-Mode Interference) can be used. In addition, the multiplexer 104 may have a configuration in which a spatial optical system is used for multiplexing and the combined light is incident on the EAM.

In this semiconductor laser device 100, for example, the temperature detected by the temperature detector 107, Tc=30 to 60° C., is the operating temperature range. The temperature detector 107 may be configured to measure the temperature of the semiconductor optical integrated device 10 on which the DFB laser and EAM are mounted. The semiconductor optical integrated device 10 is a very small device on the order of mm, and almost no temperature distribution occurs in the device. Further, since the temperature inside the package incorporating the semiconductor optical integrated device 10 is substantially equal to the temperature inside the semiconductor optical integrated device 10, there is almost no temperature distribution inside the package. Therefore, the temperature measurement location may be anywhere within the package. Here, the temperature detector 107 has an accuracy of 5° C., that is, 30° C., 35° C., 40° C., and so on, so that the output temperature values Tc of the temperature detector 107 are discrete at equal intervals of 5° C. It is a normal temperature, and the value between them is not output. The operation of the laser selection controller 106 selects the semiconductor laser LD1 at 30° C.≦Tc≦35° C. The semiconductor laser LD1 has an oscillation wavelength λLD1 of 1305 nm at 35°C. The semiconductor laser LD2 is selected at 40° C.≦Tc≦45° C., and the oscillation wavelength λLD2 at 45° C. is 1310 nm. The semiconductor laser LD3 is selected at 50° C.≦Tc≦60° C., and the oscillation wavelength λLD3 at 55° C. is 1315 nm.

The temperature dependence dλLD/dT of the oscillation wavelength of the DFB laser is 0.1 nm/°C. Here, comparing the oscillation wavelengths of the respective DFB lasers at a temperature of 35° C., LD1 is 1305 nm, LD2 is 1309 nm, and LD3 is 1313 nm. In this way, three DFB lasers LD1, LD2, LD3 having different oscillation wavelengths at the same temperature are mounted, and the DFB lasers are switched and operated depending on the temperature range.

As described above, the temperature dependence dλLD/dT of the oscillation wavelength of the DFB laser is 0.1 nm/°C. On the other hand, the temperature dependence dλEA/dT of the absorption peak wavelength λEA at which the light absorption of EAM becomes a peak is 0.5 nm/°C, and λEA=1240 nm at 35°C, λEA=1245 nm at 45°C, and λEA=55°C. The absorption layer has a thickness of 1250 nm. FIG. 2 shows the difference between the laser oscillation wavelength λLD and the absorption peak wavelength λEA of EAM, Δλ=λLD−λEA. For example, when Tc=40° C., the semiconductor laser LD2 is selected. Since the temperature detector outputs the detected temperature Tc in steps of 5° C., when Tc=40° C., the actual temperature T is not necessarily 40° C. However, assuming that the actual temperature T is 40° C., λLD2 ( T=40° C.)=1309.5 nm. On the other hand, λEA (T=40° C.)=1242.5 nm, and Δλ=67 nm. From FIG. 2, by selecting the semiconductor lasers LD1, LD2, LD3 based on the detected temperature Tc, Δλ fluctuates within a range of 30 to 60° C. within a range of 63 to 67 nm, and the fluctuation amount is suppressed to a sufficiently small fluctuation amount. You can

FIG. 3 shows an algorithm for selecting and operating the laser. Here, an example will be described in which the temperature detector 107 outputs the detected temperature Tc with an accuracy of 5° C., that is, in steps of 5° C., as described above. The laser selection controller 106 stores a look-up table as shown in FIG. 3, in which a laser to be selected and a current value to be supplied to the selected laser are associated with each other at discrete temperatures of 5° C. ing. When the detected temperature Tc is transmitted from the temperature detector 107 to the laser selection controller 106 (step ST1), the laser corresponding to Tc and its current value are read from the stored look-up table (step ST2), and according to the read information. A semiconductor laser is selected, and an instruction is made to flow the read current value to the selected semiconductor laser (step ST3).

The timing at which the detected temperature Tc is transmitted from the temperature detector 107 to the laser selection controller 106 may be every fixed period, or may be the timing at which the detected temperature Tc changes. For example, when the detected temperature Tc detected by the temperature detector 107 changes from 35° C. to 40° C., Tc is transmitted to the laser selection controller. The laser selection controller 106 selects the DFB laser LD2 corresponding to 40° C. and instructs the DFB laser LD2 to flow a current of 60 mA. When the detected temperature Tc changes from 40° C. to 45° C., an instruction is given to change the current value flowing through the DFB laser LD2 from 60 mA to 65 mA. When the detected temperature Tc rises from 45° C. and changes to 50° C., the DFB laser LD3 is selected, and a command is made to flow a current of 70 mA to the DFB laser LD3. When the detected temperature Tc drops from 45° C. and changes to 40° C., an instruction is given to change the current value flowing through the DFB laser LD2 from 65 mA to 60 mA.

As described above, the temperature change rate of the absorption peak wavelength of EAM is 0.5 nm/° C., and the temperature change rate of the oscillation wavelength of the DFB laser is 0.1 nm/° C. The oscillation wavelength of the DFB laser changes according to the temperature dependence of the refractive index of the diffraction grating, but the absorption peak wavelength of the EAM changes according to the temperature dependence of the semiconductor band gap, so that such a difference occurs. Therefore, if the semiconductor laser device has only the DFB laser LD2 having the characteristic shown by the dotted line in FIG. 2 and the bias voltage of the EAM is not adjusted, Δλ fluctuates in the range of 59 to 71 nm in the temperature range of 30 to 60° C. However, the amount of fluctuation is large. The value of Δλ changes due to temperature change, and Δλ changes by 12 nm at 30° C. and 60° C. In the case of the first embodiment shown by the solid line, by switching the DFB laser in the three temperature ranges, the difference between the maximum value and the minimum value of Δλ is 4 nm. The performance of EAM depends on this Δλ. FIG. 4 shows the Δλ dependence of the extinction ratio when modulated by EAM. The change in extinction ratio when Δλ changes from 59 nm to 71 nm by 12 nm is about 7 dB, but the change in extinction ratio when 4 nm changes from 63 nm to 67 nm is about 2 dB. According to the first embodiment, the fluctuation of the extinction ratio can be suppressed without controlling the temperature of the semiconductor optical integrated device by the Peltier device or the like and without adjusting the bias voltage of the EAM according to the temperature.

In the example of FIG. 3, the temperature is read with an accuracy of 5° C. and the laser to be selected and the current value are specified. However, for example, a lookup table is specified for each discrete temperature of 1° C. It is also possible to define it with a function. When the accuracy of the detected temperature is increased, it is considered that the operation near the threshold temperature at which the selected laser or the current value is changed becomes unstable. In this case, stable operation can be ensured by providing a so-called hysteresis operation in which the switching temperature of the laser is made different when the temperature rises and when it falls. For example, when the lookup table is specified with an accuracy of 1° C., switching from LD1 to LD2 is performed when the temperature rises and 41° C. is detected, and switching from LD2 to LD1 is performed at a temperature of It is a method of performing when the temperature is lowered and 39° C. is detected.

When the look-up table is specified for each discrete temperature and the accuracy of the temperature detector 107 is the same as this discrete temperature interval, that is, when the look-up table is specified for each 5° C., the temperature detection is performed. When the accuracy of the temperature detector 107 is set to 5° C., or when the accuracy of the temperature detector 107 is set to 1° C. when the lookup table is designated every 1° C., the operation automatically becomes a hysteresis operation. For example, when the lookup table is specified for each 1°C, when the detected temperature Tc changes from 39°C to 40°C when the temperature rises, the DFB laser selection corresponding to 40°C and the set value of the current value are performed. That is, when the temperature decreases, when the Tc changes from 40° C. to 39° C., the DFB laser corresponding to 39° C. is selected and the current value is set. This operation is a hysteresis operation. Further, for example, when the detected temperature changes to 40° C. when the temperature rises, as shown in the lookup table of FIG. 3, the DFB current value is increased, so the temperature of the semiconductor optical integrated device changes in the direction of further increase. On the other hand, when the temperature is decreased to 35° C. when the temperature is decreased, the DFB current value is decreased, so that the temperature of the semiconductor optical integrated device is changed to be further decreased. This characteristic also emphasizes the hysteresis operation and realizes stable operation.

The accuracy of the detected temperature Tc output by the temperature detector 107 is not the same as the value of the discrete temperature intervals stored in the look-up table as described above, and even if the accuracy is equal to or higher than this interval value. Good. That is, the interval between the values of the detected temperature Tc output by the temperature detector 107 may be an interval equal to or smaller than the value of the discrete temperature interval stored in the lookup table. For example, the accuracy of the temperature detector 107 is 0.1° C., that is, the detected temperature Tc of the temperature detector 107 is output at intervals of 0.1° C., and the lookup table is set every 5° C. as shown in FIG. The configuration may be stored. In this case, for example, at 30.0° C.≦Tc≦34.9° C., the laser selection controller 106 selects the DFB laser LD1 and instructs the DFB laser LD1 to flow a current value of 50 mA. When Tc changes from 34.9° C. to 35.0° C., the laser selection controller 106 commands to change the current value of the DFB laser LD1 to 55 mA. At 35.0° C.≦Tc≦39.9° C., the laser selection controller 106 selects the DFB laser LD1 and instructs the DFB laser LD1 to flow a current value of 55 mA. When Tc changes from 39.9° C. to 40.0° C., the laser selection controller 106 selects the DFB laser LD2 and instructs the DFB laser LD2 to flow a current value of 60 mA. At 40.0° C.≦Tc≦44.9° C., the laser selection controller 106 selects the DFB laser LD2 and instructs the DFB laser LD2 to flow a current value of 60 mA. When the temperature drops and Tc changes from 40.0° C. to 39.9° C., the DFB laser LD1 is selected, and the laser selection controller 106 commands the DFB laser LD1 to flow a current value of 55 mA. As described above, when the accuracy of the temperature detected by the temperature detector 107 is high, the hysteresis operation described above is particularly effective. For example, when the temperature rises and the Tc changes from 39.9°C to 40.0°C, the selection of the DFB laser is switched from LD1 to LD2, while when the temperature falls, the temperature changes from 39.1°C to 39.0°C. In that case, it is preferable to perform a hysteresis operation such as switching from LD2 to LD1.

In the above description, an example in which DFB lasers with different three wavelengths are selected has been described. However, if the number of DFB lasers is four or more, that is, if different DFB lasers with four or more wavelengths are mounted, the variation due to temperature of Δλ becomes smaller, or The range of operable temperature can be expanded.

As described above, according to the semiconductor laser device of the first embodiment, it is possible to operate in a wide temperature range without having a temperature adjusting function, so that it is possible to reduce power consumption and further, the EAM for each temperature. No need to adjust bias. Furthermore, since only semiconductor lasers having different wavelengths are selected, the laser selection controller 106 has a simple structure. As shown in FIG. 2, for example, when only the DFB laser LD2 and EAM are provided, when the temperature changes between 30 and 60° C., Δλ varies from 59 nm to 71 nm over a wide range. When the bias voltage of the EAM is fixed and used, if the semiconductor laser does not have a selection function, the fluctuation amount of the extinction ratio at 30 to 60° C. is 7 dB, but when the semiconductor laser device 100 of the first embodiment is used, the extinction The amount of specific fluctuation can be suppressed to 2 dB.

Embodiment 2.
FIG. 5 is a schematic block diagram showing the structure of the semiconductor laser device according to the second embodiment. The semiconductor laser device 100 is a semiconductor optical integrated device in which three semiconductor lasers (here, DFB lasers) LD1, LD2, LD3 having different oscillation wavelengths, a multiplexer 104 for multiplexing them, and one EAM 105 are mounted. 10 are provided. Further, a temperature detector 107 such as a thermistor for detecting the temperature of the semiconductor optical integrated device 10, and a laser selection controller for selecting and operating one of the three semiconductor lasers according to the detection temperature Tc of the temperature detector 107. 106 and an EAM bias controller 108 that adjusts the bias voltage of the EAM according to the temperature Tc detected by the temperature detector 107.

Hereinafter, as in the case of the first embodiment, the case where the accuracy of the detected temperature Tc of the temperature detector 107 is 5° C. and the look-up table is specified for each discrete temperature of 5° C. will be described. This semiconductor laser device 100 has a working temperature range of Tc=−40 to 90° C. The operation of the laser selection controller 106 selects the semiconductor laser LD1 at −40° C.≦Tc≦0° C. The oscillation wavelength λLD1 of the semiconductor laser LD1 at a temperature of −20° C. is 1287.5 nm. The semiconductor laser LD2 is selected when 5° C.≦Tc≦45° C. The oscillation wavelength λLD2 of the semiconductor laser LD2 at a temperature of 25° C. is 1310 nm. The semiconductor laser LD3 is selected at 50° C.≦Tc≦90° C. The oscillation wavelength λLD3 of the semiconductor laser LD3 at a temperature of 70° C. is 1323 nm. The temperature dependence dλLD/dT of the oscillation wavelength λLD of the DFB laser is 0.1 nm/°C, the temperature dependence dλEA/dT of the absorption peak wavelength λEA of EAM is 0.5 nm/°C, and the dependence of the bias voltage Vc is 20 nm. /V. FIG. 6 shows the temperature dependence of λEA for five values of Vc. The median value of Vc shown in FIG. 6, λEA at Vc=−1.2V, is λEA (T=−20° C.)=1222.5 nm, λEA (T=25° C.)=1245 nm, λEA (T=70° C.) = 1267.5 nm. According to the lookup table shown in FIG. 7, for example, when Tc=25° C., the semiconductor laser LD2 is selected, λLD2 (T=25° C.)=1310 nm, and the bias voltage Vc of EAM is selected to be −1.2V. .. λEA (T=25° C., Vc=−1.2V)=1245 nm and Δλ=65 nm. Based on the detected temperature Tc, by selecting a laser and setting Vc as shown in the lookup table of FIG. 7, Tc=−40 to 90° C. and Δλ fluctuates in the range of 63 to 65 nm. Therefore, it is possible to suppress the variation of the effective Δλ due to the temperature within a narrow range.

FIG. 7 also shows an operation algorithm when selecting a laser. The detected temperature Tc is transmitted from the temperature detector 107 to the laser selection controller 106 and the EAM bias controller 108 (step ST21). As shown in FIG. 7, the laser selection controller 106 preliminarily selects a DFB laser corresponding to a detected temperature Tc from a look-up table in which a DFB laser selected for each discrete temperature and a current value to be set are stored. The current values set for the laser and the DFB laser are read (step ST22), and a command is made to flow a specified current value to the selected DFB laser (step ST23). The EAM bias controller 108 also reads the bias voltage Vc corresponding to the detected temperature Tc from the look-up table (step ST24), and commands the EAM to apply a predetermined bias voltage Vc (step ST25). With such a control method, it is possible to suppress the variation amount of Δλ within a sufficiently small range.

As described above, in the second embodiment, not only the semiconductor laser is selected and switched but also the EAM bias voltage Vc is changed by the set value for each detected temperature, so that the semiconductor laser is only selected according to the detected temperature. As compared with the first embodiment, the variation amount of Δλ with temperature is suppressed, and it is possible to operate in a wider temperature range.

Embodiment 3.
FIG. 8 is a schematic block diagram showing the configuration of the semiconductor laser device 100 according to the third embodiment. The semiconductor laser device 100 is a semiconductor optical integrated device in which three semiconductor lasers (here, DFB lasers) LD1, LD2, LD3 having different oscillation wavelengths, a multiplexer 104 for multiplexing them, and one EAM 105 are mounted. 10 are provided. Further, a photocurrent detector 109 for detecting a photocurrent flowing when the EAM 105 absorbs light and a photocurrent detected by the photocurrent detector 109 select and operate one of the three semiconductor lasers. A laser selection controller 106 is provided.

The temperature and the EAM photocurrent value when each laser is operated are measured in advance. Since the response speed of the photocurrent detection circuit is sufficiently slower than the signal modulation speed, the photocurrent value output by the photocurrent detector 109 is not affected by the EAM modulation rate. Determine the range of photocurrent values in the temperature range where it operates properly, that is, the upper threshold value and the lower threshold value, and determine the selected laser and its current value so that the photocurrent value is between the upper threshold value and the lower threshold value. , A table as shown in FIG. 9 is obtained. In FIG. 9, the photocurrent value is shown as an absolute value. In addition, the temperature range in the table of FIG. 9 is for reference and is not always necessary for the lookup table.

FIG. 10 shows a flow of operations. First, the photocurrent value is read (step ST31), and when the photocurrent value (absolute value) exceeds the upper limit threshold value (YES in step ST32), the DFB laser on the higher temperature side than the DFB laser that has been operated until then is selected. When the photocurrent value exceeds the lower limit threshold value (YES in step ST32), the DFB laser is switched to the low temperature side and operated (step ST35). If neither is the case, the selected DFB laser is not changed and the setting is not changed (step ST36). The above routine is performed, for example, at regular intervals. For example, it is assumed that a current of 60 mA is flowing through the semiconductor laser LD2 in the laser initial state. The photocurrent detector 109 sends the value of the photocurrent to the laser selection controller 106, and the laser selection controller 106 reads it. When the value exceeds 5.4 mA, the laser selection controller 106 determines that the upper limit threshold of the photocurrent is exceeded, switching to the high temperature side laser is performed, and 70 mA is supplied to the semiconductor laser LD3 to operate.

Alternatively, when the detected value of the photocurrent exceeds the upper limit threshold or the lower limit threshold stored in the lookup table, the photocurrent detector 109 notifies the laser selection controller 106 of information indicating that the upper limit threshold or the lower limit threshold is exceeded. The DFB laser to be operated by the laser selection controller 106 may be switched.

In the third embodiment, instead of detecting the temperature, the laser is switched by utilizing the temperature dependence of the photocurrent of EAM. FIG. 11 shows an example of the temperature dependence of the photocurrent of the semiconductor lasers LD1, LD2, LD3. When the temperature rises, the effective Δλ decreases, the amount of light absorbed increases, and the photocurrent value (absolute value) increases. When this value reaches the threshold of the lookup table, the semiconductor laser is switched to the adjacent semiconductor laser.

Although the configuration in which only the semiconductor laser is selected is described here, a configuration in which the bias voltage of the EAM is changed based on the detected value of the photocurrent may be added as in the case of the second embodiment. it can.

According to the third embodiment, the semiconductor laser device can be further downsized as compared with the first embodiment, since an accessory such as a temperature detector is not required.

Fourth Embodiment
FIG. 12 is a schematic block diagram showing the structure of the semiconductor laser device 200 according to the fourth embodiment. Here, a DBR (Distributed Bragg Reflector) laser is used as the semiconductor laser 120. The DBR laser 120 and the EAM 105 are mounted on the semiconductor optical integrated device 20. The DBR laser 120 includes a distributed Bragg reflector region 121 and a gain region 122 as a configuration. When the injection current of the distributed Bragg reflector region 121 is changed, the oscillation wavelength of the DBR laser 120 is changed. Therefore, the DBR controller 123 changes the injection current of the distributed reflection region 121 to change the oscillation wavelength of the DBR laser 120 according to the detection temperature Tc of the temperature detector 107, thereby changing the oscillation wavelength λDBR of the DBR laser 120 and the EAM 105. It is possible to suppress the difference in the absorption peak wavelength λEA and the variation in Δλ=λDBR−λEA.

Hereinafter, as in the case of the first embodiment, the case where the accuracy of the temperature Tc detected by the temperature detector 107 is 5° C. will be described. In this semiconductor laser device 200, for example, Tc=30 to 60° C. is the operating temperature range. By the operation of the DBR controller 123, 20 mA is selected as the current of the distributed Bragg reflector region 121 when 30° C.≦Tc≦35° C. The oscillation wavelength λDBR of the DBR laser 120 at a temperature of 35° C. is 1305 nm. When 40° C.≦Tc≦45° C., 5 mA is selected as the current of the distributed Bragg reflector region 121. The oscillation wavelength λDBR at a temperature of 45° C. is 1310 nm. When 50° C.≦Tc≦60° C., 0 mA is selected as the current of the distributed Bragg reflector region 121. The oscillation wavelength λDBR at a temperature of 55° C. is 1315 nm. The temperature dependence dλEA/dT of the absorption peak wavelength λEA of EAM105 is 0.5 nm, λEA (T=35°C)=1240 nm, λEA (T=45°C)=1245 nm, λEA (T=55°C)=1250 nm, It has an absorption layer such that Δλ at this time is shown in FIG. For example, when Tc=40° C., 5 mA is selected as the current in the distributed Bragg reflector region 121. λDBR (T=40° C.)=1309.5 nm. On the other hand, λEA (T=40° C.)=1242.5 nm and Δλ=67 nm. From FIG. 13, it can be seen that Δλ fluctuates in the range of 63 to 67 nm in the range of 30 to 60° C. and can be suppressed to a sufficiently small fluctuation range.

FIG. 14 shows an example of the operation algorithm and lookup table. The temperature Tc detected by the temperature detector 107 is transmitted to the DBR controller 123 (step ST41). The DBR controller 123 reads the distributed reflection region current value corresponding to the temperature from a preset look-up table (step ST42), and sets the current value of the distributed reflection region 121 (step ST43). For example, if the detected temperature Tc is 35° C., the current value of the distributed Bragg reflector region 121 is set to 20 mA. When Tc reaches 40° C., the current value of the distributed Bragg reflector region 121 is set to 5 mA. With such a control method, by changing the wavelength of the DBF laser in accordance with the detected temperature Tc, it is possible to suppress the variation amount of Δλ within a sufficiently small range even if the temperature changes.

Further, as described in the second embodiment, as shown in FIG. 15, an EAM bias controller 108 that changes the EAM bias voltage in accordance with the detected temperature may be provided. Thereby, the operable temperature range can be further expanded.

Further, as described in the third embodiment, as shown in FIG. 16, instead of detecting the temperature, the DBR controller 123 causes the DBR controller 123 to use the value of the photocurrent detected by the photocurrent detector 109. It is also possible to adopt a configuration in which the current value of is switched. For example, a lookup table as shown in FIG. 17 is stored, and when the photocurrent value exceeds the lower limit threshold value, the distributed reflection region current value is changed to a low temperature side value, and the photocurrent value becomes the upper limit threshold value. The DBR controller 123 may be controlled to change the distributed reflection region current value to a value on the high temperature side when it exceeds.

As described above, in the semiconductor laser device including the semiconductor optical integrated device 20 including the DBR laser and the EAM, by adjusting the current value of the distributed reflection region of the DBR laser based on the value of the temperature or the photocurrent, The semiconductor laser device can be uncooled in a wide temperature range.

Although various exemplary embodiments and examples are described in this application, various features, aspects, and functions described in one or more embodiments may be The present invention is not limited to the application, and can be applied to the embodiments alone or in various combinations. Therefore, innumerable variations not illustrated are envisioned within the scope of the technology disclosed herein. For example, it is assumed that at least one component is modified, added or omitted, and at least one component is extracted and combined with the components of other embodiments.

10, 20 semiconductor optical integrated device, 100, 200 semiconductor laser device, 104 multiplexer, 105 EAM, 106 laser selection controller, 107 temperature detector, 108 EAM bias controller, 109 photocurrent detector, 120 semiconductor laser ( DBR laser), 121 distributed reflection region, 122 gain region, 123 DBR controller, LD1, LD2, LD3 semiconductor laser (DFB laser)

Claims (12)

Multiple DFB lasers with different oscillation wavelengths,
A combiner for combining the outputs of the plurality of DFB lasers;
An EAM that modulates the light output from the multiplexer,
A temperature detector for measuring temperature,
A semiconductor laser device comprising: a laser selection controller for selecting and switching a DFB laser to be operated among the plurality of DFB lasers based on the temperature detected by the temperature detector. A lookup table that stores the discrete temperatures and the DFB lasers selected for each temperature and the operating current values of the selected DFB lasers in association with each other is provided. 2. The semiconductor laser device according to claim 1, wherein the DFB laser to be selected is selected based on stored information. 3. The semiconductor laser device according to claim 2, wherein the accuracy of the temperature detected by the temperature detector is an accuracy equal to or higher than the value of the discrete temperature interval stored in the look-up table. 2. The semiconductor laser device according to claim 1, further comprising an EAM bias controller that controls the bias voltage of the EAM based on the temperature detected by the temperature detector. A lookup table that stores discrete temperatures, the DFB laser selected for each temperature, the operating current value of the selected DFB laser, and the bias voltage of the EAM in association with each other is stored in the lookup table. 5. The semiconductor laser device according to claim 4, wherein the laser selection controller selects the DFB laser to be selected, and the EAM bias controller sets a bias voltage of the EAM according to the information provided. The semiconductor laser device according to claim 5, wherein the accuracy of the temperature detected by the temperature detector is equal to or higher than the value of the discrete temperature interval stored in the lookup table. Multiple DFB lasers with different oscillation wavelengths,
A combiner for combining the outputs of the plurality of DFB lasers;
An EAM for modulating the light output from the multiplexer,
A photocurrent detector for measuring the photocurrent of the EAM,
A semiconductor laser device comprising: a laser selection controller for selecting and switching a DFB laser to be operated among the plurality of DFB lasers based on a value of a photocurrent detected by the photocurrent detector. 8. The semiconductor laser device according to claim 7, further comprising an EAM bias controller that controls the bias voltage of the EAM based on the value of the photocurrent detected by the photocurrent detector. A DBR laser having an active region and a distributed reflection region,
An EAM that modulates the light output from the DBR laser,
A temperature detector for measuring temperature,
A semiconductor laser device comprising: a DBR controller that controls an injection current into the distributed reflection region based on the temperature detected by the temperature detector. The semiconductor laser device according to claim 9, further comprising an EAM bias controller that controls a bias voltage of the EAM based on the temperature detected by the temperature detector. A DBR laser having an active region and a distributed reflection region,
An EAM that modulates the light output from the DBR laser,
A photocurrent detector for measuring the photocurrent of the EAM,
A semiconductor laser device comprising: a DBR controller that controls an injection current into the distributed reflection region based on a value of a photocurrent detected by the photocurrent detector. The semiconductor laser device according to claim 11, further comprising an EAM bias controller that controls the bias voltage of the EAM based on the value of the photocurrent detected by the photocurrent detector.

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