JP2012058432A - Semiconductor gain area-integrated mach-zehnder modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor gain area-integrated Mach-Zehnder (MZ) modulator module that enables stable transmission.SOLUTION: A semiconductor laser-integrated Mach-Zehnder modulator comprises a semiconductor laser and a Mach-Zehnder modulator that modulates light emitted from the semiconductor laser with AC signals and outputs the modulated light, which are integrated over a chip. When temperature variation occurs, the extinction ratio of the light outputted from the Mach-Zehnder modulator is increased by controlling the AC signals according to variations in chip temperature (including controls on the amplitude of the AC signals and the bias voltage of the AC signals).

Description

  The present invention relates to a semiconductor gain region integrated Mach-Zehnder (MZ) modulator used as a light source for optical communication.

  With the widespread use of broadband networks, movements to increase the communication speed to 10 Gbit / s or higher in metro optical communication networks connecting cities / relay stations have become active. Metro-based optical communication networks require long-distance transmission over a fiber transmission distance of 40 km or more. In the optical communication system for the metro optical communication network, downsizing and low power consumption of the optical transceiver module are important issues.

  In order to reduce the size and power consumption of the optical transceiver module, so-called “uncooled” which does not require a temperature adjusting mechanism of the light emitting device is effective. In the direct modulation method that generates an optical signal by directly applying an electrical signal to a semiconductor laser, for example, 10Gbit at an operating temperature range of 100 ° C or higher due to the selection of materials that are resistant to temperature changes and improved heat dissipation in the device structure. Uncooled high-speed operation of / s is realized. However, in the direct modulation method, for example, time fluctuation (hereinafter referred to as chirping) of the signal light wavelength is large during high-speed modulation operation with a modulation speed of 10 Gbit / s or more. For this reason, the signal light wavelength band is used in the 1300 nm band where the dispersion of the optical fiber is small. However, the signal light wavelength band of 1300 nm has a large propagation loss in the optical fiber and is not suitable for long-distance transmission over 30 km.

  Therefore, an uncooled operation of a DFB laser (one form of gain region) integrated EA modulator suitable for long-distance transmission has been studied. The light absorption layer of the EA modulator uses a quantum well structure in which the well layer is made of either InGaAlAs, InGaAsP or InGaAs, and the barrier layer is made of either InGaAlAs or InAlAs. By appropriately setting the composition wavelength of the barrier layer in the quantum well structure to be used, it is possible to simultaneously suppress insertion loss, secure extinction ratio, and suppress chirping over a wide temperature range from -5 ℃ to 85 ℃. Is possible. However, it has been found that it is difficult to achieve the required optical output (for example, fiber output + 1 dBm) in the EA modulator, since the absorption loss in the modulator portion becomes large particularly at high temperatures. In particular, transmission over a transmission distance of 40 km or even 80 km is expected to be difficult with the current technology. Therefore, it is conceivable to apply a semiconductor MZ modulator that can be integrated with the DFB laser and has a small absorption loss in the modulator section. However, since the characteristics of a semiconductor MZ modulator change greatly depending on the temperature, a semiconductor laser and an MZ modulator are conventionally mounted on a Peltier device, and the temperature is adjusted to around 50 ° C. at room temperature or higher. (For example, Patent Document 1).

  FIG. 1 shows a top view of a DFB laser integrated MZ modulator using a DFB laser as a gain region. This MZ modulator is formed by laminating a semiconductor layer and an electrode on an n-type InP substrate 1. From the light input side (left side of FIG. 1) to the output side (right side of FIG. 1), there is a region where a laminated body of the DFB laser semiconductor layer 2 and the DFB laser electrode 9, a duplexer 3, and MZ optical waveguide electrodes 10, 11 The laminated MZ optical waveguides 4 and 5, the multiplexing / demultiplexing optical waveguide 6, the output optical waveguide 7, and the photodetector electrode 12 are connected to the laminated monitor optical waveguide 8. The monitor optical waveguide 8 incorporates a photodetector.

  The light emitted from the DFB laser semiconductor layer 2 is bifurcated into a MZ optical waveguide 4 and an MZ optical waveguide 5 by a one-to-two demultiplexer 3 and input to a two-to-two multi / demultiplexed optical waveguide 6. The signal light is coupled to the output optical waveguide 7 and / or the monitor optical waveguide 8 depending on the interference condition between the light passing through the MZ optical waveguide 4 and the light passing through the MZ optical waveguide 5. The interference condition is controlled by changing the refractive indexes of the MZ optical waveguide 4 and the MZ optical waveguide 5 according to the voltage applied to the MZ optical waveguide electrode 10 and the MZ optical waveguide electrode 11. The photodetector electrode 12 outputs the light intensity detected by the photodetector.

  FIG. 2 shows the principle explanation of the modulation operation of the MZ modulator in the case of push-pull driving. Push-pull driving is a driving method in which high-frequency signals having opposite phases are applied to the MZ waveguide electrode 10 and the MZ waveguide electrode 11, and the driving voltage can be halved, which is effective for power saving of the modulator driver. FIG. 2A shows an example of the voltage dependence of the optical output of the MZ modulator. The optical output depends on the voltage difference between the voltage V2 applied to the MZ waveguide electrode 11 and the voltage V1 applied to the MZ waveguide electrode 10. Here, no light is output at V2-V1 = 0V, and light is output most strongly at V2-V1 = Vmax. FIG. 2B shows an example of a time waveform of the push-pull drive voltage. V2 changes with the amplitude Vpp2 around the bias voltage Vb2, and V1 changes with the amplitude Vpp1 around the bias voltage Vb1. V1 and V2 are in opposite phases. FIG. 2 (c) shows an example of the time waveform of the optical output. When V2-V1 = Vmax, the light output is maximum, and when V2-V1 = 0 (V), the light output is minimum, and these are repeated.

  FIG. 3 shows a configuration diagram of a transmitter module using a conventional temperature-adjusted DFB laser integrated MZ modulator. The basic configuration of the DFB laser integrated MZ modulator 52 is the same as that shown in FIG. In an optical transmitter module housing 54, a DFB laser integrated MZ modulator 52, a thermometer 51, a laser drive circuit 62, an MZ modulator drive circuit 59 with bias adjustment, termination resistors 53 and 58, and an optical fiber 56 are stored. The laser electrode is connected to a laser drive circuit terminal 63 by a wire 64, and the MZ electrodes 10 and 11 are connected to MZ drive circuit terminals 60 and 61 and termination resistors 53 and 58 by wires 65, 66, 55 and 57. The DFB laser integrated MZ modulator 52 is fixed on the Peltier element 91. The temperature adjustment circuit 95 is connected to the thermometer 51 through a wire 92 at a thermometer terminal 93, and is connected to the Peltier element 91 and a wire 96 through a Peltier element terminal 94. The photodetector electrode is connected to the light absorption region control electrode 81 connected to the photodetector circuit 82 by a wire 83.

  FIG. 4 shows a block diagram of a transmitter module using the DFB laser integrated MZ modulator of FIG. The temperature adjustment circuit 95 drives the Peltier element 91 based on the signal from the thermometer 51 to keep the temperature constant. The light detection circuit 82 controls the laser drive circuit 62 based on the signal from the light detector 71 and adjusts the signal supplied to the DFB laser electrode 29 to keep the light output constant. The MZ modulator drive circuit 59 supplies a drive signal to the MZ electrodes 10 and 11 according to the setting at the time of module manufacture, and generates an optical signal having a high extinction ratio.

JP 2007-93717

IEEE Photon. Tech. Lett., Vol. 9, No.3, pp. 380-382, 1997.

  As described above, the cooled operation of the DFB laser integrated MZ modulator has been studied. However, the uncooled operation of the DFB laser integrated MZ modulator has not been sufficiently studied.

Since the demand for a power-saving light source has increased in recent years, the present inventors have studied the uncooled operation of the DFB laser integrated MZ modulator. When the operating temperature of the prototype laser integrated MZ modulator was changed, the modulation characteristics changed greatly. Further, the DFB laser integrated MZ modulator operating near the normal room temperature does not operate well due to the change in the difference between the laser oscillation wavelength λ _DFB and the MZ modulator absorption edge wavelength λ _MZ . The above two will be described together with the temperature dependence of the MZ modulator absorption edge wavelength λ _MZ and the oscillation wavelength λ _DFB of the DFB laser.

In the case of a semiconductor MZ modulator, the quantum confined Stark effect (QCSE) is mainly used to change the refractive index due to voltage application. Further, with respect to the temperature coefficient λ _MZ /T=0.7nm/K of lambda _MZ, the temperature coefficient λ _DFB /T=0.1nm/K of lambda _DFB. The temperature coefficient of the difference ΔH (λ _DFB −λ _MZ ) is ΔH / T = −0.6 nm / K, and ΔH changes depending on the temperature. In QCSE, the amount of change in refractive index decreases as ΔH increases. Therefore, as ΔH increases with decreasing temperature, the amount of change in the refractive index of the waveguide with respect to voltage application decreases. FIG. 5 shows the extinction characteristics at various temperatures. This is a case where ΔH at a temperature of 25 ° C. is set to 120 nm and ΔH changes according to a temperature coefficient ΔH / T = −0.6 nm / K. If the temperature is 25 ° C and V2-V1 is changed from 0V to -1.4V, the light output extinction ratio is high and turns on and off. On the other hand, at 85 ° C., when driving under the same conditions, the light is turned off and turned off again, so that appropriate on / off characteristics cannot be obtained. Further, at 85 ° C., even when the light output is maximum, the light intensity is as low as about 0.4, and it is a problem that an appropriate on / off characteristic cannot be obtained.

  Furthermore, there are the following problems. The light intensity output from the optical modulator needs to be constant. In general, the lower the temperature, the higher the efficiency of the DFB laser. Therefore, the lower the temperature, the lower the driving current of the DFB laser (FIG. 6A). On the other hand, if there is return light due to residual reflection on the front end face of the chip, it is known that the DFB oscillation state is affected, and as a result, so-called chirp occurs, and transmission characteristics deteriorate (for example, Non-patent document 1). This phenomenon is suppressed if the relaxation oscillation frequency is high (7 GHz or more). FIG. 6B shows the temperature dependence of the relaxation oscillation frequency at the operating current of FIG. 6A. The relaxation oscillation frequency is 8 GHz at a high temperature, but the relaxation oscillation frequency decreases as the drive current decreases at a low temperature, and the relaxation oscillation frequency is 6 GHz at a temperature of −5 ° C. That is, the problem that transmission characteristics deteriorate at low temperatures occurs.

  An object of the present invention is to provide a gain region integrated MZ modulator in which a gain region for single mode oscillation that enables stable transmission is integrated.

  The present application includes a plurality of means for achieving the above object, and an example thereof is as follows.

  A semiconductor gain region integrated type Mach-Zehnder modulator in which a gain region for outputting single-wavelength light and a Mach-Zehnder modulator for modulating and outputting light emitted from the gain region by an AC signal are integrated. Semiconductor gain region integration characterized by suppressing fluctuations in the extinction ratio of light output from the Mach-Zehnder modulator by controlling the AC signal according to the change in the chip temperature when the temperature changes Type Mach-Zehnder modulator.

  According to the present invention, a gain region integrated MZ modulator module capable of stable transmission is realized.

It is a top view of the DFB laser integrated MZ modulator of a prior art example. It is a principle explanatory view of the modulation operation of the MZ modulator in the case of push-pull drive. It is a block diagram of the transmitter module using the temperature-adjusted DFB laser integrated MZ modulator of a prior art example. It is a block diagram of a transmitter module using a conventional DFB laser integrated MZ modulator. It is a figure which shows the temperature characteristic of the quenching of the conventional MZ modulator. It is a graph which shows the temperature characteristic of the conventional DFB laser current. It is a graph which shows the temperature dependence of the relaxation oscillation frequency in the operating current of FIG. 6A. 1 is a top view of a DFB laser integrated MZ modulator of Example 1. FIG. FIG. 3 is a cross-sectional view of the DFB laser integrated MZ modulator of Example 1 taken along the line A-A ′. 1 is a configuration diagram of an optical transmitter module using a DFB laser integrated MZ modulator of Example 1. FIG. 2 is a control block diagram of the optical transmitter module according to the first embodiment. 6 is a graph showing the V2-V1 dependence of the light output of Example 1. 6 is a graph showing the temperature dependence of the extinction ratio of the MZ modulator of Example 1. 3 is a graph showing temperature dependence of a drive voltage of the MZ modulator of Example 1. It is a graph which shows (DELTA) H @ 85 degreeC dependence of the optical output maximum value in 85 degreeC of the MZ modulator of Example 1. FIG. 6 is a graph showing the dependency of the extinction ratio at 85 ° C. of the MZ modulator of Example 1 on ΔH @ 85 ° C. FIG. 6 is a configuration diagram of a transmitter module using the DFB laser integrated MZ modulator of Embodiment 2. FIG. FIG. 6 is a control block diagram of the optical transmitter module according to the second embodiment. It is a top view of a DFB laser integrated MZ modulator. It is B-B 'sectional drawing of a DFB laser integrated MZ modulator. 6 is a configuration diagram of an optical transmitter module using a DFB laser integrated MZ modulator of Example 3. FIG. 6 is a graph showing temperature characteristics of current and voltage supplied to a light absorption region control electrode 81 which is an electrode of a light absorption region. 6 is a graph showing temperature characteristics of a DFB laser current of Example 3. It is a graph which shows the temperature dependence of the relaxation oscillation frequency in the operating current of FIG. 18A. FIG. 10 is a control block diagram of the optical transmitter module according to the third embodiment.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  Example 1 will be described with reference to FIGS. 7A, 7B, 8, 9, 10A, 10B, 11, 12A, and 12B.

  Example 1 is an optical transmitter module in which a 1.55 μm band DFB laser and an MZ modulator are integrated on an n-type InP substrate. The feature of the first embodiment is that a thermometer is arranged in the vicinity of the chip, and the driving condition of the MZ modulator is set based on the temperature measured by the thermometer.

  7A is a top view of the DFB laser integrated MZ modulator, FIG. 7B is a cross-sectional view taken along the line A-A ′ of the DFB laser integrated MZ modulator, and FIG. 8 is a configuration diagram of the optical transmitter module.

  The DFB laser integrated MZ modulator of the present embodiment is composed of a semiconductor stacked body sandwiched between a leftmost high-reflectance coating 32 and a rightmost non-reflective coating 33. From the left end, the gain region 22, one relay optical waveguide optically coupled to the gain region 22, and one MMI (Multi Relay Wave) that is the input of the one relay optical waveguide and the output of the two relay waveguides -Mode Interference) A demultiplexer 23 composed of waveguides, an MZ optical waveguide 24 and an MZ optical waveguide 25 in two relay waveguides which are outputs of the demultiplexer 23, an MZ optical waveguide 24 and an MZ The two relay waveguides after the optical waveguide 25 are the input and the two relay waveguides are the output. The two-to-two multiplexer 26 and one of the two output waveguides of the multiplexer 26 are A connected output waveguide 27 and a detection waveguide including a photodetector 71 connected to the other are arranged side by side.

  As shown in FIG. 7B, the gain region includes an active layer 41, a diffraction grating 46, a p-type InP cladding 47, a p-type InGaAs contact layer 44, and a DFB laser electrode 29 on an InP substrate 21 having a common electrode 43 on the entire back surface. Are stacked in order.

  As shown in FIG. 7B, in the MZ region, the active layer 42, the p-type InP clad 47, the p-type InGaAs contact layer 44, and the MZ electrodes 24 and 25 are sequentially laminated on the InP substrate 21 having the common electrode 43 on the entire back surface. It is a structure that has been.

As shown in FIG. 7B, the photodetection region includes the light absorption layer InGaAs 73, the p-type InP clad 47, the p-type InGaAs contact layer 44, and the photodetector electrode 72 on the InP substrate 21 having the common electrode 43 on the entire back surface. In order,
As shown in FIG. 7B, the portion of the InP substrate 21 where no electrode is present is covered with a SiO ₂ passivation film 45.

  The gain region has a diffraction grating 46, which constitutes a DFB laser. Then, laser oscillation occurs by passing a current between the DFB laser electrode 29 on the surface of the InP substrate 21 and the common electrode 43 on the back surface of the InP substrate 21.

  The MZ region is configured to perform a modulation operation by applying a reverse phase voltage through the MZ electrodes 30 and 31.

  The light intensity absorbed by the light absorption layer InGaAs is detected through the photodetector 71.

  As shown in FIG. 8, a DFB laser integrated MZ modulator 52, a thermometer 51, a laser drive circuit 62, and an MZ modulator with bias adjustment are driven in an optical transmitter module housing 54 into which a fiber 56 is inserted. A circuit 59, a light detection circuit 82, termination resistors 53 and 58, and an optical fiber 56 are accommodated. The laser electrode is connected to the laser drive circuit terminal 63 by the wire 64, the MZ electrode is connected to the MZ drive circuit terminals 60 and 61 and the terminating resistors 53 and 58 by the wires 65, 66, 55 and 57, and the photodetector electrode 72 is The photodetection circuit terminal 81 on the photodetection circuit 80 is connected by a wire 83. In all the embodiments of the present application, a temperature adjusting element represented by a Peltier element is not arranged.

  FIG. 9 shows a block diagram. Based on the signal from the thermometer 51, the temperature adjustment circuit 95 controls the MZ electrodes 30 and 31 to generate an optical signal having a high extinction ratio. The light detection circuit 75 adjusts the laser drive circuit 62 based on the signal from the light detector 71 to keep the light output constant.

  FIG. 10A shows the V2-V1 dependency of the optical output of the first embodiment, and FIG. 10B shows the temperature dependency of the extinction ratio of the MZ modulator of the first embodiment. FIG. 11 shows the temperature dependence of the drive voltage of the MZ modulator of the first embodiment. As shown in FIG. 10A, the laser active layer 41 and the MZ part active layer 42 are designed so that ΔH at a temperature of 85 ° C. is 120 nm. At other temperatures, ΔH becomes ΔH / T = −0.6 nm / K according to ΔH / T = −0.6 nm / K. Changed. Furthermore, as shown in FIG. 11, at a temperature of 85 ° C., V2−V1 = 0V is minimum and V2−V1 = −1.4V is maximum, so Vb1 = −0.35V, Vb2 = −1.05V, Vpp1 = An optical waveform with a high extinction ratio of 12 dB was realized by setting Vpp2 = 0.7V.

  Next, consider the case of a temperature of 50 ° C. Under the same driving conditions as in the case of 85 ° C., the light output is 0.7 times the light output at 85 ° C. even when the light output is the largest, that is, the extinction ratio is 9.5 dB, which is lower than that at 85 ° C. Therefore, as shown in FIG. 10B, the extinction ratio is as high as 12 dB by controlling the driving conditions with the LUT (look-up table) set as Vb1 = −0.5V, Vb2 = −1.5V, Vpp1 = Vpp2 = 1.0V. An optical waveform with

  As described above, in the optical transmitter module of the present embodiment, the driving conditions are controlled by the LUT in which Vb1, Vb2, Vpp1, and Vpp2 are set as shown in FIG. 7 according to the temperature measured by the thermometer 51. Specifically, the drive conditions were set in units of 0.1 ° C. so that Vb1, Vb2, Vpp1, and Vpp2 each increased as the temperature decreased. As a result, a high extinction ratio of 12 dB or higher was always achieved even when the chip temperature varied between -5 ° C and 85 ° C. Note that more accurate drive condition control may be performed using a function instead of control using the LUT.

  Next, the design of ΔH will be described. As shown in FIG. 5, when ΔH is designed at a normal operating condition temperature of 25 ° C., the light output is 0.4 at the maximum at the highest chip temperature (for example, 85 ° C.), and a good extinction ratio cannot be obtained. . This is because light absorption occurs when a voltage is applied due to the QCSE effect. This light absorption decreases with decreasing temperature. This indicates that ΔH needs to be designed so that absorption does not occur at the highest chip temperature used. FIG. 12A shows the ΔH @ 85 ° C. dependency of the maximum light output at 85 ° C., and FIG. 12B shows the ΔH @ 85 ° C. dependency of the extinction ratio at 85 ° C. When ΔH <100 nm, the extinction ratio deteriorates due to light absorption and becomes 10 dB or less. Therefore, in order to obtain a high extinction ratio of 10 dB or more, it is necessary to design with ΔH> 100 nm.

  When ΔH at 85 ° C. was set to 120 nm, as shown in FIG. 10B, a good optical waveform exceeding an extinction ratio of 10 dB was obtained at a temperature of −5 to 85 ° C.

  A second embodiment will be described with reference to FIGS.

  The second embodiment is also an optical transmitter module in which a 1.55 μm band DFB laser and an MZ modulator are integrated on an n-type InP substrate.

  The feature of the second embodiment, which is different from the first embodiment, is that the driving condition of the MZ modulator is controlled by the output of the thermometer 51 in the first embodiment, but in the second embodiment, instead of arranging the thermometer 51, The detection signal of the photodetector 71 arranged in front of (behind) the MZ modulator is used not only for the output control of the DFB laser but also for controlling the driving conditions of the MZ modulator.

  Here, the design was such that ΔH = 120 nm at a temperature of 85 ° C. As a result, the light output characteristics as shown in FIG. 6A were obtained.

Here, automatic bias control (ABC) generally used in LiNbO ₃ MZ modulators is controlled by using an MZ modulator drive circuit 59 with bias adjustment, a photodetector circuit 75, and a photodetector 71. To do.

  FIG. 14 shows a block diagram. Based on the signal from the photodetector 71, the ABC circuit of the photodetector circuit 75 controls the signal supplied to the MZ electrodes 30 and 31 to generate an optical signal having a high extinction ratio. At the same time, the laser drive circuit 62 is adjusted based on the signal from the photodetector 72 to keep the light output constant.

  As a result, as in Example 1, a good optical waveform exceeding the extinction ratio of 10 dB was obtained in the temperature range of -5 ° C to 85 ° C.

  A third embodiment will be described with reference to FIGS. 15A, 15B, 16, 17, 17, 18A, 18B, and 19. FIG.

  Example 3 is also an optical transmitter module in which a 1.55 μm band DFB laser and an MZ modulator are integrated on an n-type InP substrate.

  15A is a top view of the DFB laser integrated MZ modulator, FIG. 15B is a BB ′ sectional view of the DFB laser integrated MZ modulator, FIG. 16 is a configuration diagram of the optical transmitter module, and FIG. 17 is a light absorption region. FIG. 18A shows the temperature characteristics of the DFB laser current of Example 3 and FIG. 18B shows the relaxation with the operating current of FIG. 18A. FIG. 19 is a control block diagram of the optical transmitter module according to the third embodiment.

  The features of the third embodiment are as shown in FIGS. 15A, 15B and 16 in that the DFB laser integrated MZ modulator of the first embodiment is provided with a light absorption region, a light absorption region control electrode 91, and a light absorption region. A feature is that a control terminal 92 and a wire 93 are added.

  The operation of the light absorption region will be described. FIG. 17 shows the temperature dependence of the operating conditions of the light absorption region. At high temperatures, it becomes transparent by injecting current. On the other hand, at a low temperature, a negative voltage is applied to absorb the light from the DFB laser and make the input light to the MZ modulator and the output light intensity to the optical fiber constant. As a result, the output light intensity to the optical fiber is kept constant, the drive current of the DFB laser at a low temperature and the relaxation oscillation frequency are suppressed from decreasing, and the transmission characteristics are prevented from deteriorating. As a result, as shown in FIG. 18A, the driving current at a low temperature becomes larger than that when there is no light absorption region. As shown in FIG. 18B, the relaxation oscillation frequency at a low temperature is increased, and deterioration of transmission characteristics is suppressed.

  Here, the DFB laser active layer is used as the light absorption layer as it is, but another layer may be formed by selective growth.

  FIG. 19 shows a block diagram. Based on the signal from the light detector 71, the light detection circuit 82 uses an ABC circuit to control the signal supplied to the MZ electrodes 30 and 31 to generate an optical signal having a high extinction ratio. In parallel, based on the signals from the photodetector 71 and the thermometer 51, the laser drive circuit 62 adjusts the signals supplied to the laser electrode 29 and the light absorption region control electrode 91 to keep the light output constant. .

  As a result, a good optical waveform exceeding an extinction ratio of 10 dB was obtained in the temperature range of -5 ° C to 85 ° C.

<Common items>
In Examples 1 to 3, the semiconductor layered structure of the DFB laser has been adopted as the gain region. However, since the output of the gain region only needs to be a single wavelength, it is assumed to be combined with an external single wavelength light source. As an alternative, the gain region may be replaced with an optical amplifier (SOA).

1: n-type InP substrate, 2: DFB laser semiconductor layer, 3: demultiplexer, 4, 5: MZ optical waveguide, 6: multiplexing / demultiplexing optical waveguide, 7: output optical waveguide, 8: monitor optical waveguide, 9: DFB laser electrode,
10, 11: MZ optical waveguide electrode, 12: photodetector electrode,
21: n-type InP substrate, 22: gain region, 23: demultiplexer, 24, 25: MZ electrode, 26: multiplexer, 27: output waveguide, 29: DFB laser electrode,
30, 31: MZ electrode, 32: High reflectivity coating, 33: Non-reflective coating,
41: laser active layer, 42: MZ part active layer, 43: common electrode, 44: p-type InGaAs contact layer, 45: SiO ₂ passivation film, 46: diffraction grating, 47: p-type InP cladding,
51: Thermometer, 52: DFB laser integrated MZ modulator, 53, 58: Termination resistor, 54: Optical transmitter module housing, 55, 57, 65, 66: Wire, 56: Optical fiber, 59: MZ modulator Drive circuit,
60, 61: MZ drive circuit terminal, 62: Laser drive circuit, 63: Laser drive circuit terminal, 64, 65, 66: Wire,
71: Photodetector, 72: Photodetector electrode, 73: Light absorption layer, 75: Photodetection circuit, 80: Photodetection circuit, 81: Electrode for light absorption region control, 82: Photodetection circuit, 83, 96: Wire: 91: Peltier element, 92: Light absorption region control terminal, 95: Temperature adjustment circuit.

Claims (13)

A semiconductor gain region integrated Mach-Zehnder modulator in which a gain region that outputs single-wavelength light and a Mach-Zehnder modulator that modulates and outputs light emitted from the gain region by an AC signal are integrated on a chip. ,
A semiconductor gain characterized by suppressing fluctuations in the extinction ratio of light output from the Mach-Zehnder modulator by controlling the AC signal in accordance with the change in the chip temperature when a change occurs in the chip temperature. Area integrated Mach-Zehnder modulator. In claim 1,
The gain region is a DFB laser or an optical amplifier, and a semiconductor gain region integrated Mach-Zehnder modulator. In claim 1,
The control of the AC signal is control of a bias voltage of the AC signal. A semiconductor gain region integrated type Mach-Zehnder modulator, wherein: In claim 1,
The control of the AC signal is control of the amplitude of the AC signal. A semiconductor gain region integrated type Mach-Zehnder modulator, characterized in that: In claim 3,
The control of the AC signal is control of the amplitude of the AC signal. A semiconductor gain region integrated type Mach-Zehnder modulator, characterized in that: In claim 1,
A thermometer for measuring a chip temperature of the laser integrated Mach-Zehnder modulator;
A semiconductor gain region integrated type Mach-Zehnder modulator, wherein the control signal of the AC signal is determined according to the output of the thermometer when the AC signal is controlled according to a change in the chip temperature. In claim 4,
A pair of Mach-Zehnder arms constituting the Mach-Zehnder modulator are supplied with a first AC signal and a second AC signal,
The semiconductor gain region integrated type Mach-Zehnder modulator, wherein the amplitude of the first and second AC signals is larger as the temperature is lower. In claim 5,
A pair of Mach-Zehnder arms constituting the Mach-Zehnder modulator are supplied with a first AC signal and a second AC signal,
The semiconductor gain region integrated type Mach-Zehnder modulator, wherein the amplitude of the first and second AC signals is larger as the temperature is lower. In claim 1,
By supplying a first AC signal and a second AC signal to a pair of Mach-Zehnder arms constituting the Mach-Zehnder modulator, the Mach-Zehnder modulator performs a push-pull operation.
A semiconductor gain region integrated type Mach-Zehnder modulator, wherein the reference voltage of the first AC signal and the second reference voltage are increased negatively as the temperature decreases. In claim 1,
The Mach-Zehnder modulator includes a semiconductor layer,
A semiconductor gain region integrated type Mach-Zehnder modulator characterized by having an extinction ratio of 10 dB or more at a chip temperature of room temperature or higher. In claim 1,
An optical output monitor for measuring optical output from the laser integrated Mach-Zehnder modulator;
A semiconductor gain region integrated type Mach-Zehnder modulator, wherein the control signal of the AC signal is determined according to the output of the optical output monitor when the AC signal is controlled according to the output change of the output monitor. In claim 1,
At the highest temperature among lasers exceeding 50 ° C and the temperature at which the Mach-Zehnder modulator operates
A semiconductor gain region integrated type Mach-Zehnder modulator characterized in that the semiconductor layer has a material composition so that the output light from the laser is substantially transmitted through the semiconductor layer under a driving voltage condition in which the optical output is on. . In claim 1,
A semiconductor gain region integrated Mach-Zehnder modulator comprising a light absorption region between the semiconductor laser and the Mach-Zehnder modulator when the chip temperature is not more than room temperature.

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