JP4690569B2 - Semiconductor laser device and optical transmitter using the same. - Google Patents

Description

[0001]
[Technical field belonging to the invention]
The present invention relates to a semiconductor laser device and an optical transmission device using the same, and more specifically, a semiconductor electroabsorption modulator integrated laser that monitors a part of the output of the semiconductor laser and controls the driving current of the semiconductor laser. The present invention also relates to an optical transmission device using a semiconductor electroabsorption modulator integrated light source that controls the optical output of a semiconductor laser.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a semiconductor electroabsorption modulator integrated light source used in an optical communication system has an optical transmission module structure shown in FIG. 1 for a transmission rate of about 10 Gbit / s. The optical transmission module 101 includes a laser module 102, a laser driving current source 103, a modulator driving unit 104, a bias amplitude control unit 105, and a temperature control circuit 116 in the package. A semiconductor electroabsorption modulator integrated laser (hereinafter abbreviated as EA (electro-absorption) modulator integrated laser) 106 is mounted on a Peltier substrate 112 in the main part of the laser module 102. The EA modulator integrated laser 106 includes a distributed feedback laser (hereinafter abbreviated as DFB laser) unit 107 driven by a constant current and an EA modulator unit 108 operated by a modulation voltage. The EA modulator turns on and off the light of the DFB laser by shifting the EA modulator active layer absorption edge using the quantum confined Stark effect generated by applying a voltage to the EA modulator. It is a modulator. MAoki, et.al., “High-speed (10 Gbit / s) and low-drive-voltage (1 V peak to peak) InGaAs / InGaAsP MQW electroabsorption modulator integrated DFB laser with semi -insulating buried heterostructure, ”Electron. Lett., vol.28, pp. 1157-1158, 1992.
[0003]
A termination resistor 110 is mounted in parallel on the EA modulator 108 to achieve impedance matching. Further, in front of the EA modulator integrated laser 106, optical means for coupling the light c from the laser to the optical fiber 117 through the lens 113, the isolator 115, and the lens 114 is provided. Further, an optical output monitoring photodiode 109 is mounted behind the EA modulator integrated laser. A monitor current Im photoelectrically (O / E) converted by the photodiode 109 passes through the laser drive current source 103 to control the DFB laser 107 to keep the optical output of the laser 107 constant, so-called auto power control (APC). ) A loop is formed. Here, all of the laser drive current sources 103 output linearly with respect to the input current.
[0004]
[Problems to be solved by the invention]
Optical transmitter equipped with EA modulator integrated laser Is In addition to the currently commercialized transmission distance of 40 km, long-distance transmission of 80 km and 100 km or more will continue in the future. When the long-distance transmission is advanced, the EA modulator integrated laser is required to have characteristics of high light output, low chirp, and large extinction ratio. When these characteristics are improved in the EA modulator integrated laser, the characteristic that deteriorates accordingly is the front-rear specific linearity ΔPf / ΔIm described below. This is because, in any case of improving the characteristics, the light absorption in the EA modulator integrated laser EA modulator section increases, and the linearity of the EA modulator integrated laser front light output is non-linear with respect to the laser drive current. This is because the front-rear specific linearity of the element itself is deteriorated because of the influence. This will be described in more detail.
The EA modulator integrated laser 106 of the EA modulator integrated light source has an EA modulator 108 integrated in front of the DFB laser 107. Due to its nature, the EA modulator absorbs light from the DFB laser 107 even when no voltage is applied. Therefore, the output of the light c from the front of the EA modulator integrated laser 106 is extracted as a light output obtained by subtracting the light absorption of the EA modulator section from the light output a of the DFB laser 107. On the other hand, as for the output of the light b from the rear of the EA modulator integrated laser 106, the optical output of the DFB laser is taken out as it is because there is no EA modulator in the rear.
[0005]
Further, in order to stably operate the EA modulator integrated light source by APC control, the ratio of the monitored EA modulator integrated laser rear light output b to the front light output c is a constant value within the laser drive current range. Must be kept on. Because, for example, when the rear light output doubles for a certain amount of current increase, if the front light output only becomes 1.5 times, the APC control by the rear light output monitor stabilizes the front light output. This is because it becomes impossible to control.
[0006]
In the conventional EA modulator integrated light source, the relationship between the output signal from the photodiode 109 and the optical output of the lens 114 is shown in FIG. 2 by indicating the output signal Ip from the photodiode 109 with a dotted line. The output Io is indicated by a solid line. Here, since the output signals Ip and Io are normalized by the output of the laser drive current; If = 150 mA, the vertical axis is not an absolute value.
[0007]
In FIG. 2, the output Io of the light c from the front of the EA modulator 108 does not completely coincide with the output Ip from the rear of the EA modulator 108 even though it is standardized. In the region of about 80 mA from the current Ith, the output Io (solid line) is small. This is because the EA modulator 108 is integrated in front of the EA modulator integrated laser 107. Since the output of the light a from the front of the laser 107 passes through the EA modulator 108 and is output from the optical fiber 117 via the lenses 113 and 114 and the isolator 115, the light of the DFB laser 107 is integrated in the same element. The EA modulator 108 is absorbed. Even when the EA modulator 108 is not driven, that is, when the EA modulator section is not biased, this absorption occurs at a photocurrent of about 10 mA, and the laser driving current is 80 mA from the threshold current (Ith). It occurs remarkably in the area. On the other hand, since no absorber is integrated behind the EA modulator integrated laser, a coupling loss occurs with the photodiode 109, but a value proportional to the output of the DFB laser 107 is 106. Output.
[0008]
The laser module 106 controls the front light output to be constant by monitoring the rear output. Therefore, even when the laser drive current If changes, if the ratio of the front output to the rear output is not constant within a certain range, it cannot be controlled to the same front output as before the laser drive current If changes. .
[0009]
In this regard, FIG. 3 shows the current dependence of an actual EA modulator integrated laser, where the ratio of the rear output Im and the front output Pf is the front-rear ratio. In the figure, as shown by the solid line A in the conventional current dependency, it can be seen that the front-rear ratio varies with the drive current If. This is due to the difference between the rear light output Ip and the front light output Io in FIG. In the laser drive current If region that generates an optical output in which the light absorption of the EA modulator is significant, that is, in the region where the laser drive current If is 80 mA from the threshold current, the front-to-back ratio is not constant. The driving current If increases with an increase. On the other hand, in the laser drive current region that generates an optical output in which the light absorption of the EA modulator section is at a saturation level, the front-rear ratio with respect to the laser drive current If is substantially constant.
[0010]
Usually, the laser drive current is If = 60 to 80 mA, but in order to guarantee long-term reliability, it is necessary to guarantee a value of 50% increase, that is, If = 90 to 120 mA. Therefore, for example, a module that is initially operated at If = 70 mA must guarantee a current that is above the threshold that is the drive current range, for example, an operation from 30 mA to 105 mA, as shown in FIG. When the front-to-back ratio is If = 30 mA and 105 mA, the forward / backward ratio fluctuates by about 20%. When this fluctuation exceeds 20%, it becomes difficult to operate the optical output signal constantly. As an indicator of this tolerance, the current fluctuation of the front-rear output ratio is
ΔPf / ΔIm = [{Pf (105 mA) / Pf (30 mA)} / {Im (105 mA) / Im (30 mA)}]-1 When this value is not less than ± 20%, as described above Reliability cannot be guaranteed for a long time. In addition, since the EA modulator tends to be saturated at a certain light input level, the ratio between the rear light output and the front light output further varies. Therefore, when the laser output current is controlled by converting the rear light output linearly with a monitor photodiode and the ratio between the rear light output and the front light output varies, the light output in front of the laser is controlled to be constant. It becomes difficult to do.
[0011]
For this reason, conventionally, by performing the operating current at If = 65 mA, the optical element is selected by selecting the laser element so that the front-rear specific linearity value is ± 20% or less with respect to the actual value +15 to + 22%. High reliability is realized. Therefore, the product yield is poor and uneconomical, it can be used over a wide range of operating current, and the product life cannot be extended. This variation is known to vary depending on the characteristics of the EA modulator, for example, the extinction characteristic. In an optical transmission device using a semiconductor EA modulator integrated laser designed for long-distance transmission, this variation is more noticeable. There are problems that arise.
[0012]
Accordingly, the main object of the present invention is to realize an electroabsorption modulator integrated laser device in which the drive current of the semiconductor laser has a small fluctuation in the ratio of the rear light output and the front light output over a wide range and an optical transmission device using the same. It is to be.
[0013]
[Means for Solving the Problems]
To achieve the above object, the present invention provides an optical means for optically coupling the front output light of a semiconductor electroabsorption modulator integrated laser to an optical fiber, and monitors the rear output light of the conductor electroabsorption modulator integrated laser. In a semiconductor laser device having a monitor photodiode and a laser driving power source that is controlled by the monitor photodiode and generates a driving current of the semiconductor laser of the semiconductor electroabsorption modulator integrated laser,
A non-linear amplifier in which the monitor photodiode output monitor current has an amplification factor that changes with respect to the value of the laser drive current is provided between the monitor photodiode and the laser drive power supply. Here, the semiconductor laser device includes a laser module, an optical transmission module, and an optical transmission / reception module described in the embodiments.
[0014]
The present invention solves the problem of the conventional electroabsorption EA modulator integrated light source by converting the rear monitor current with a non-linear amplifier by the control means and outputting the converted current as a laser drive current. is doing. The non-linear amplifier described above has a function of correcting the fluctuation of the front-rear specific linearity of the semiconductor EA modulator integrated laser with respect to the drive current.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
<Example 1>
FIG. 4 is a configuration diagram of an embodiment of an optical transmission apparatus (optical transmission module) according to the present invention. In this embodiment, an EA modulator integrated laser having a transmission rate of 10 Gbit / s is mounted. The basic configuration of the optical transmission module 401 is almost the same as the description in FIG. Components that are substantially the same as those in FIG. 1 are assigned the same reference numerals and symbols as in FIG. The difference in configuration from that of FIG. 1 is that the output current Ip O / E converted by the photodiode 109 is input to the laser light output stabilization circuit via the non-linear amplifier 402.
[0016]
The non-linear amplifier 402 receives the monitor current Ip, converts it into a non-linear type, and outputs it. The output current Iq of the non-linear amplifier 402 is input to the semiconductor laser 107 via the laser driving current source 103. This non-linear conversion means conversion in which the amplification factor changes with respect to the level of the monitor current Ip that is an input. Specifically, the forward light output of the EA modulator integrated laser 106 is small, and the light absorption in the EA modulator 108 integrated in front of the EA modulator integrated laser does not reach the saturation level, and significant light absorption is observed. In this case, the amplification factor of the nonlinear amplifier at this time is N1. On the other hand, in the case of the EA modulator integrated laser front light output level in which the light absorption with respect to the light input of the laser integrated in the EA modulator 108 part reaches the saturation region, in other words, the EA modulator part photocurrent is In the case where the saturation level is reached with respect to the laser light input, the amplification factor of the nonlinear amplifier 402 at this time is N2. Non-linear conversion is defined by conversion that gives a relationship of N1 <N2 to the amplification factor of the non-linear amplifier in each region.
[0017]
As can be seen from the above description, the nonlinear conversion should originally change the amplification factor according to the light input level to the EA modulator portion of the EA modulator integrated laser, but the optical input to this EA modulator is: Since there is a one-to-one correspondence with the input level of the monitor current, the effect of the present invention can be obtained by conversion in which the amplification factor changes with respect to the input level of the monitor current Ip. Furthermore, since the optical input to the EA modulator 108 has a one-to-one correspondence with the drive current of the EA modulator integrated laser, nonlinear conversion is also defined as conversion in which the amplification factor changes with respect to the laser drive current region. can do. A characteristic example of the nonlinear amplifier 402 will be described with reference to FIGS.
[0018]
FIG. 5 is a graph showing the nonlinear amplifier output with respect to the laser driving current If, and FIG. 6 is a graph showing the amplification factor of the nonlinear amplifier with respect to the laser driving current If, both of which are two of the two nonlinear amplifiers A and B. An example case is shown.
[0019]
The amplification action in the case shown in FIGS. 5 and 6 will be described. The non-linear amplifier A as the first example is in a laser drive current region of about 80 mA from the threshold value Ith where light absorption in the EA modulator 108 does not reach the saturation level and significant light absorption is observed. As shown in FIGS. 5 and 6, the amplification factor is N1. On the other hand, if the amplification factor in the laser drive current If region of 70 mA or more where the EA modulator photocurrent reaches the saturation level with respect to the laser beam input is N2, the relationship is N1 <N2.
[0020]
Another example of the non-linear amplifier B is shown in FIGS. The characteristic of the nonlinear amplifier B is that the amplification factor N3 is a function of If in the region from the threshold value Ith to 70 mA. In this case as well, the amplification factor N4 in the region where the amplification factor N3 is greater than the laser drive current of 70 mA The relationship is N3 (If) <N4. In actual use, the non-linear amplifier 402 can selectively use the A type or the B type according to the characteristics of the EA modulator integrated laser. Such a nonlinear amplifier 402 can be realized by forming a circuit by combining active elements and passive elements, or by programming a desired amplification factor in a microcomputer.
[0021]
FIG. 7 is a block diagram of a configuration example of the nonlinear amplifier.
The non-linear amplifier 402 includes a current / voltage conversion circuit 403 that converts the monitor current Ip into a voltage, a memory (ROM) 404 in which front output information is written in advance, and the output voltage of the current / voltage conversion circuit 403 as the front output information. The front / rear correction circuit 405 includes a small processor that executes a program to be corrected based on the forward / backward correction circuit.
[0022]
FIG. 8 is a characteristic diagram of the nonlinear amplifier 402. The operation of the nonlinear amplifier 402 will be specifically described with reference to the laser drive current If. The monitor current Ip that is input to the non-linear amplifier 402 is as shown by the non-linear amplifier input Ip in FIG. 8, but the non-linear amplifier output Iq is converted to the monitor current shown by the characteristic Iq in FIG. Here, since the currents Ip and Iq in FIG. 8 are normalized by the output of the laser drive current If = 150 mA, the vertical axis is not an absolute value. When the current dependency is taken with respect to the ratio between the monitor current Iq through the nonlinear amplifier 402 and the light output Io in front of the laser, the current dependency is higher than that of the conventional one as shown by a dotted line B in FIG. I understand that it is small. Accordingly, even when the laser drive current If changes, the ratio of the front output to the rear output is substantially constant, so that it can be controlled to the same front output as before the laser drive current If changes.
[0023]
For example, a module that is initially operated with a drive current If = 70 mA must guarantee an operation up to a minimum current value in a drive current range; 30 mA to a maximum current value; 105 mA, but as shown in FIG. When the rear ratio B is If = 30 mA and 105 mA, the fluctuation is smaller than that of the conventional A. Therefore, even when the current fluctuates, the optical output signal can be operated in a range of about ± 10%. When indicated by the index of current fluctuation ΔPf / ΔIm (refer to the prior art) of the front-to-back ratio linearity, the value of the front-to-back ratio linearity is improved from the conventional +15 to + 22% to a ± 10% distribution centering on 0% be able to. This improvement effect can be obtained by converting the monitor current into a drive current dependency similar to the front light output of the laser by a non-linear amplifier. Further, the dependence of the monitor current on the drive current after conversion by the nonlinear amplifier is determined by the characteristics of the nonlinear amplifier, and further, the current dependence of the longitudinal linearity can be determined. Therefore, a highly reliable optical transmitter can be realized by designing a non-linear amplifier so that a desired front-to-back ratio linearity characteristic can be obtained as an optical transmitter module.
[0024]
Also, in FIG. 4, the components for controlling the EA modulator integrated laser to a constant temperature, the Peltier 112, the thermistor 113, and the temperature control circuit 116 are shown in FIG. Even in the case of a semiconductor laser module that does not require temperature control, the effect of the present invention does not change.
Further, in FIG. 4 of the embodiment, it goes without saying that the same effect can be obtained even in a so-called simple package in which the aspherical lens 113, the selfoc lens 114, and the isolator 115 are not provided. .
<Example 2>
FIG. 9 shows a configuration of another embodiment of the optical transmission module according to the present invention. In this embodiment, an EA modulator integrated laser having a transmission rate of 10 Gbit / s is mounted.
The basic configuration of the optical transmission module 601 in FIG. 9 is substantially the same as the optical transmission module 106 in FIG. 4 described in the first embodiment, and substantially the same components as those in FIG. The detailed explanation is omitted. The difference between the configuration of FIG. 9 and the configuration of FIG. 4 is that the nonlinear amplifier 802 is mounted in the semiconductor laser module 601. The output current Ip O / E converted by the photodiode 109 becomes the monitor current output Iq of the semiconductor laser module via the non-linear amplifier 802 mounted in the semiconductor laser module.
[0025]
The operation of the non-linear amplifier 802 is the same as that described in the first embodiment, whereby the ratio of the optical output to the optical fiber 117 of the semiconductor laser module 601 and the monitor current output Iq via the non-linear amplifier 802 is as shown in FIG. As shown by the dotted line B in FIG. 6, the fiber light output can be controlled to be constant even when the laser drive current changes.
[0026]
In the embodiment shown in FIG. 9, the components for controlling the EA modulator integrated laser 601 to a constant temperature, the Peltier 112 and the thermistor 111 are described. However, these components are not provided, and a semiconductor which does not require temperature control. Even in the case of a laser module, the effect of the present invention does not change.
Further, in the embodiment shown in FIG. 9, it goes without saying that the same effect can be obtained even in a so-called simple package in which the aspheric lens 113, the Selfoc lens 114, and the isolator 115 are not provided.
[0027]
Further, even in a semiconductor laser module with a built-in wavelength locker equipped with a wavelength locking mechanism for wavelength multiplexing transmission, when this semiconductor laser is a laser integrated with an EA modulator, the present invention can be used to drive current. A highly reliable semiconductor laser module with a built-in wavelength locker in which the fiber light output can be controlled to be constant with respect to the fluctuation of the wavelength can be manufactured.
<Example 3>
An embodiment of the present invention will be described with respect to an optical transmission apparatus having a transmission rate of 10 Gbit / s. By mounting the optical transmission module described in the first embodiment and configuring the optical transmission device, the optical output is controlled to be constant regardless of the variation of the semiconductor EA modulator integrated laser driving current due to the change with time and the environmental change. Therefore, an optical transmission device having high long-term reliability is realized. Further, by constructing an optical transmission system using this optical transmission apparatus, a highly reliable optical transmission system can be realized.
<Example 4>
FIG. 10 shows the configuration of another embodiment of an optical transmission apparatus (optical transmission module) equipped with an EA modulator integrated wavelength tunable laser according to the present invention.
The basic configuration of the transmission module 901 is almost the same as that described in the first embodiment (FIG. 4), but the difference is that the EA modulator integrated wavelength tunable laser 902 is mounted in FIG. . The EA modulator integrated wavelength tunable laser 902 is characterized in that the semiconductor laser part is composed of a wavelength tunable laser 903 and an EA modulator part 108.
[0028]
Even in the case of the wavelength tunable laser, since the EA modulator is integrated in front of the wavelength tunable laser, the EA modulator integrated wavelength tunable laser element itself has a longitudinal linearity similar to that described in the first embodiment. It has drive current dependency. Further, since the absorption characteristic of the EA modulator portion changes because the wavelength is changed, the current dependency of the front-to-back ratio linearity may increase compared to the transmission module in which the wavelength of Example 1 does not change. sell. For this reason, the optical output can be controlled to be constant even when the semiconductor laser driving current fluctuates by mounting the nonlinear amplifier in the same manner as in the first embodiment and configuring the optical transmission module.
<Example 5>
FIG. 11 shows the configuration of still another embodiment of an optical transmission apparatus (optical transmission module) equipped with an EA modulator integrated wavelength tunable laser according to the present invention.
The basic configuration of the semiconductor laser module 1001 is almost the same as that described in the second embodiment, except that an EA modulator integrated wavelength tunable laser 902 is mounted in FIG. The EA modulator integrated wavelength tunable laser 902 is characterized in that the semiconductor laser part is composed of a wavelength tunable laser 903 and an EA modulator part 108. Also in this case, the same effect as in the second embodiment can be obtained as an EA modulator integrated wavelength tunable laser module.
[0029]
As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example. Further, as the optical transmission device of the present invention, the optical transmission module has been described, but is not limited to the optical transmission module, the optical transmission device equipped with the optical transmission module, the wavelength division multiplexing optical transmission device equipped with the optical transmission module, The present invention is also applied to an optical communication system using these optical transmission apparatuses.
In wavelength multiplexing optical transmission with a transmission speed of about 10 Gbit / s, each module has a different optical transmission module, so the individual module differences and the wavelengths of components such as filters and wavelength multiplexers in the optical transmission device Depending on the dependency, the light output level may be different. However, in the optical transmission apparatus, it is necessary to control the optical output levels of the respective wavelengths at a constant level due to the configuration of the optical transmission system. For this optical output level control, the optical transmission module described in the first embodiment is mounted and the wavelength division multiplexing optical transmission apparatus is configured, so that the optical output control suitable for the wavelength division multiplexing optical transmission apparatus can be realized, and a high long-term A reliable wavelength multiplexing optical transmission apparatus is realized.
[0030]
In addition, by constructing a wavelength optical transmission system using a wavelength division multiplexing optical transmission device, the optical output control is performed according to the wavelength-dependent components constituting the system, such as optical fiber, optical amplifier, optical switch, etc. Therefore, a highly reliable wavelength optical transmission system can be realized.
[0031]
【The invention's effect】
In the present invention, the front-rear specific linearity degradation, which is one of the important components of trunk-line optical transmission, which is the essence of the semiconductor electroabsorption modulator integrated laser, is introduced by inserting a non-linear amplifier. Since correction is performed by the laser module and the optical transmission module, the optical output stability and reliability of the semiconductor laser module and the optical transmission module are improved. Furthermore, by using these optical transmission modules, the optical output can be controlled to be constant regardless of fluctuations in the semiconductor EA modulator integrated laser drive current due to changes over time and environmental changes. The construction of a trunk optical transmission system can be realized.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing the structure of a conventional optical transmission module.
FIG. 2 is a characteristic diagram for explaining the operation of a conventional optical transmission module.
FIG. 3 is a characteristic comparison diagram of optical transmission modules according to the prior art and the present invention.
FIG. 4 is a circuit diagram of a first embodiment of a semiconductor laser device according to the present invention.
FIG. 5 is an output characteristic diagram of a nonlinear amplifier in a semiconductor laser device according to the present invention.
FIG. 6 is an amplification characteristic diagram of a nonlinear amplifier in the semiconductor laser device according to the present invention.
FIG. 7 is a configuration diagram of an embodiment of a nonlinear amplifier in a semiconductor laser device according to the present invention.
FIG. 8 is a graph showing input / output characteristics of a nonlinear amplifier in a semiconductor laser device according to the present invention.
FIG. 9 is a circuit diagram of a second embodiment of the semiconductor laser apparatus according to the present invention.
FIG. 10 is a circuit diagram of a fourth embodiment of the semiconductor laser apparatus according to the present invention.
FIG. 11 is a circuit diagram of a fifth embodiment of the semiconductor laser apparatus according to the present invention.
[Explanation of symbols]
101: Optical transmission module, 102: Semiconductor laser module,
103 ... Laser drive current source, 104 ... Modulator drive unit,
105... Bias amplitude control unit,
106 ... Electroabsorption (EA) modulator integrated DFB laser,
107 ... Electroabsorption modulator unit (EA modulator unit),
108 ... DFB laser unit, 109 ... monitor photodiode,
110 ... Terminal resistor, 111 ... Mister, 112 ... Peltier substrate,
113 ... surface lens, 114 ... selfoc lens,
115 ... isolator, 116 ... temperature control circuit,
117: optical fiber, 401: optical transmission module according to embodiment 1,
402: Non-linear amplifier,
801 ... Semiconductor laser module according to Example 2,
901: Optical transmission module according to embodiment 5;
902... EA modulator integrated wavelength tunable laser,
903 ... wavelength tunable laser unit,
1001... Optical transmission module according to Example 6

Claims (6)

Optical means for optically coupling the front output light of the semiconductor electroabsorption modulator integrated laser to an optical fiber, a monitor photodiode for monitoring the rear output light of the conductor electroabsorption modulator integrated laser, and the monitor photodiode In a semiconductor laser device having a controlled laser driving power source for generating a driving current of a semiconductor laser of the semiconductor electroabsorption modulator integrated laser,
A monitor current output from the monitor photodiode is input between the monitor photodiode and the laser drive power supply, and a non-linear amplifier whose amplification factor changes with respect to the level of the monitor current is provided .
2. The semiconductor laser device according to claim 1, wherein the nonlinear amplifier performs control to switch between two different amplification factors according to a light output level from the laser unit to the modulator unit in the semiconductor electroabsorption modulator integrated laser .   2. The semiconductor laser device according to claim 1, wherein the semiconductor laser of the semiconductor electroabsorption modulator integrated laser is composed of a wavelength tunable laser.   3. A semiconductor laser module comprising the semiconductor electroabsorption modulator integrated laser of the semiconductor laser device according to claim 1 or 2, the optical means, the monitor photodiode, and the nonlinear amplifier.   4. The semiconductor laser module according to claim 3, further comprising a modulator driving unit that drives an electroabsorption modulator in the semiconductor electroabsorption modulator integrated laser.   3. The semiconductor electroabsorption modulator integrated laser of the semiconductor laser device according to claim 1 or 2, the optical means, the monitor photodiode, the laser driving power supply, the nonlinear amplifier, and the semiconductor electroabsorption modulation. And a modulator driving unit that drives an electroabsorption modulator of the integrated laser.   2. An optical transmitter comprising: the semiconductor laser device according to claim 1; and a modulator driving unit that drives the electroabsorption modulator in the semiconductor electroabsorption modulator integrated laser.

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