JPH09219553A - Wavelength stabilizing device of semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the temperature of a semiconductor laser for making output beams oscillate in stabilized wavelength. SOLUTION: The monitor beams of a semiconductor laser 1 are converted into electric signal E1 corresponding to photointensity by the first photo-electric converter 2. A drive current control circuit 3 feeds drive current corresponding to the electric signal E1 to a semiconductor laser 1 to control the photointensity of output beams at a specific level. The output beams B of the signal beams branched by a half mirror 10 is inputted into the second photoelectric converter 12. The electric signals E2 converted to increase the output in proportion to the increase in the oscillation wavelength is equivalent to the electric signal E1 containing the variation of the oscillation wavelength. A comparison processing circuit 14 processes the wavelength variation from the electric signals E1, E2 to be compared with the reference voltage signal E3 of the set up wavelength for outputting the electric signals to a temperature control circuit 5 which controls a heating cooling element 4 by electric signals to specify the oscillation wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength stabilizing device for a semiconductor laser in a wavelength division multiplexing optical fiber transmission system or the like.

[0002]

2. Description of the Related Art A conventional wavelength stabilizing device for a semiconductor laser of this type is constructed as shown in the block diagram of FIG. In FIG. 6, reference numeral 1 denotes a signal light which is an output light having an optical intensity and an oscillation wavelength corresponding to a driving current and temperature, a semiconductor laser which outputs a monitor light, and 2 denotes an electric signal having a magnitude corresponding to the input light intensity. The first optical-electrical converter 3 for outputting outputs a drive current control circuit for controlling the drive current of the semiconductor laser 1 according to the magnitude of the input electrical signal. A heating / cooling element 5 for heating or cooling the semiconductor laser 1 is a temperature control circuit for controlling an electric signal supplied to the heating / cooling element 4 in order to keep the temperature of the semiconductor laser 1 constant.

The operation will be described below with reference to FIG.
The monitor light which is a part of the output light of the semiconductor laser 1 is
Is converted into an electric signal according to the light intensity of the monitor light. The drive current control circuit 3 controls the drive current by the converted electric signal so that the light intensity of the output light of the semiconductor laser 1 becomes constant. Further, the temperature control circuit 5 outputs an electric signal to the heating / cooling element 4 to perform control to keep the temperature of the semiconductor laser 1 constant and suppress a change in oscillation wavelength.

Conventionally, the oscillation wavelength of the output light output from the semiconductor laser is made constant by selecting the semiconductor laser or by finely adjusting the drive current and the set temperature of the semiconductor laser.

[0005]

However, in a wavelength-multiplexed optical fiber transmission system using a semiconductor laser, signal lights of different oscillation wavelengths are multiplexed and transmitted in one optical fiber cable, and multiplexed at the receiving side. A desired wavelength component is selected from the signal light using an optical filter. In such a system, if the oscillation wavelength of the signal light on the transmission side fluctuates, it deviates from the band of the optical filter and the optical intensity of the signal light output from the optical filter fluctuates, resulting in an error in the transmission information. Become. In addition, there is a problem that it interferes with the oscillation wavelength of the adjacent channel.

The present invention solves the above-mentioned problems of the prior art by detecting the wavelength change of the output light of the semiconductor laser and controlling the temperature of the semiconductor laser according to the detected change of the oscillation wavelength to oscillate. An object of the present invention is to provide a wavelength stabilization device for a semiconductor laser, which controls the wavelength to be constant and oscillates at a stable wavelength.

[0007]

In order to achieve this object, a semiconductor laser waveform stabilizing device according to the present invention uses a signal light and a monitor as output light having a light intensity and an oscillation wavelength according to a driving current and temperature. A semiconductor laser that outputs light, a first photoelectric conversion unit that converts an electric signal having a magnitude corresponding to the intensity of input light, a drive current control unit that controls a drive current of the semiconductor laser by the electric signal, and a semiconductor Heating / cooling means for heating or cooling the laser, temperature control means for controlling the electric signal supplied to the heating / cooling means to keep the temperature constant, branching means for branching the signal light of the semiconductor laser, and oscillation wavelength to be input. Optical selection means having a passage characteristic in which the light intensity changes according to the input light intensity, second photoelectric conversion means for converting into an electric signal having a magnitude corresponding to the input light intensity, and a reference electric signal according to the set wavelength. Is output, the electric signal output from the first photoelectric conversion unit and the electric signal including the change in the oscillation wavelength output from the second photoelectric conversion unit via the optical selection unit are calculated to obtain the reference electric power. And a comparison calculation means for outputting an electric signal corresponding to the comparison with the signal to the temperature control means.

Further, the wavelength stabilizing device of the semiconductor laser includes a dividing means for branching the monitor light of the semiconductor laser.

Furthermore, a semiconductor laser that outputs signal light and monitor light as output light having a light intensity and an oscillation wavelength according to the drive current and temperature, and drive current control means for controlling the drive current of the semiconductor laser by an electric signal. Heating / cooling means for heating or cooling the semiconductor laser, temperature control means for controlling an electric signal supplied to the heating / cooling means to keep the temperature constant, and monitor light of the semiconductor laser is divided into output light A and output light B. And the output light A and the output light B are input,
First and second optical selection means having light transmission characteristics that change in accordance with the oscillation wavelength and have contradictory passage characteristics, and first and second optical conversion means that convert into an electric signal having a magnitude corresponding to the input light intensity. Of the photoelectric conversion means and the electric signals output from the first and second photoelectric conversion means are compared, and when both increase and decrease change, it is determined that the light intensity changes, and when they increase and decrease opposite to each other, the oscillation wavelength change. However, it is configured so as to include a comparison calculation means for outputting an electric signal to the drive current control means or the temperature control means.

According to the above construction, in addition to the control for keeping the driving current of the semiconductor laser constant, the change in the oscillation wavelength can be detected and the temperature of the semiconductor laser can be kept constant.

Further, by branching the output light for detecting the change in the oscillation wavelength from the monitor light, the loss of the signal light can be eliminated.

Further, a change in the light intensity or a change in the oscillation wavelength can be detected by a change in the two electric signals input to the comparing and calculating means via the optical selecting means having contradictory pass characteristics.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a block diagram showing a configuration of a wavelength stabilization device for a semiconductor laser according to a first embodiment of the present invention. Here, components having the same effects as those of the constituent elements described in FIG. 6 showing the conventional example are given the same reference numerals.

In FIG. 1, 1 is a semiconductor laser and 2 is a semiconductor laser.
The photoelectric conversion means is a first optical-electrical converter for outputting an electric signal E1 corresponding to the intensity of the input light, 3 is a drive current control circuit which is a drive current control means, and 4 is a heating / cooling means. A certain heating / cooling element, 5 is a temperature control circuit which is temperature control means, 10 is a branching means, a half mirror for branching the output light from the semiconductor laser 1 into two directions, 11 is an optical selecting means, and the oscillation wavelength is An optical filter having a pass characteristic in which the light intensity monotonically increases as it increases, and the second filter 12 outputs an electric signal E2 according to the magnitude of the input light intensity.
Is a reference power source for outputting a reference electric signal E3 corresponding to the set wavelength, and 14 is a comparison calculation means for passing the electric signal E1 according to the light intensity of the semiconductor laser 1 and the optical filter 11. Is a comparison calculation circuit that calculates a wavelength variation amount from the electric signal E2 including the wavelength variation amount and outputs an electric signal corresponding to the comparison with the reference electric signal E3. FIG. 2 is a diagram showing an example of the pass characteristic of the optical filter.

The first embodiment configured as described above
The operation of the wavelength stabilization device for the semiconductor laser in FIG. First, the monitor light which is a part of the output light output from the semiconductor laser 1 is input to the first optical-electrical converter 2,
It is converted into an electric signal E1 according to the light intensity. Further, the drive current control circuit 3 supplies a drive current to the semiconductor laser 1 according to the magnitude of the input electric signal E1.
The semiconductor laser 1 outputs an output light having a light intensity according to the drive current. At this time, a feedback loop is formed for controlling the light intensity of the semiconductor laser 1, and the output light intensity can be controlled to be constant.

The signal light which is the output light of the semiconductor laser 1 is branched by the half mirror 10. Further, the branched output light B passes through the optical filter 11 and is input to the second optical-electrical converter 12. As a result, the electric signal E such that the output light intensity increases as the oscillation wavelength increases
Converted to 2. This electric signal E2 is converted into an electric signal E1 converted in accordance with the light intensity of the semiconductor laser 1 by the optical filter 1
This is a conversion of the one that includes the change in the oscillation wavelength due to passage of 1. Therefore, the electric signal E2 changes even when the light intensity of the semiconductor laser 1 changes. Therefore, the electric signal E2 and the electric signal E1 corresponding to the light intensity are input to the comparison operation circuit 14 to perform an operation of subtracting the electric signal E1 corresponding to the light intensity of the electric signal E2, and further to the set wavelength. In response to the reference voltage signal E3 output from the reference power supply 13.
An electric signal for operating the set temperature of the temperature control circuit 5 is output in comparison with. Since the oscillation wavelength of the semiconductor laser 1 changes depending on the temperature, the temperature control circuit 5 controls the heating / cooling element 4 so that the semiconductor laser 1 reaches the set temperature. Thereby, a feedback loop is formed with respect to the oscillation wavelength of the semiconductor laser 1, and the oscillation wavelength can be controlled to be constant.

As described above, according to the first embodiment,
It is possible to stabilize the oscillation wavelength by detecting the change in the oscillation wavelength of the semiconductor laser 1 and controlling the feedback loop so as to keep the oscillation wavelength constant.

FIG. 3 is a block diagram showing the structure of a wavelength stabilizing device for a semiconductor laser according to the second embodiment of the present invention. Here, components having the same functions and effects as those of the constituent elements described in FIG. 1 showing the first embodiment are designated by the same reference numerals. In FIG. 3, 1 is a semiconductor laser, 2 is a first photoelectric converter, 3 is a drive current control circuit, 4 is a heating / cooling element, 5 is a temperature control circuit, 10 is a half mirror, 11 is an oscillation wavelength. An optical filter whose pass characteristic monotonically increases as it increases, 12 is a second photoelectric converter, 13 is a reference power supply, and 14 is a comparison operation circuit.

As can be seen from the configuration shown in FIG. 3, in the first embodiment, the signal light which is the output light of the semiconductor laser 1 is split by the half mirror 10. However, in the second embodiment, the monitor light is half mirrored. It is branched by 10.
The other components and operations are the same as those in the first embodiment, and the description thereof will be omitted.

As described above, by arranging the monitor light to be split by the half mirror 10, the change in the oscillation wavelength of the semiconductor laser 1 is detected without loss of the signal light, as in the first embodiment. Then, the oscillation wavelength can be stabilized by controlling the feedback loop so that the oscillation wavelength is constant.

FIG. 4 is a block diagram showing the structure of a wavelength stabilizing device for a semiconductor laser according to the third embodiment of the present invention. Also here, the same reference numerals are given to those having the same effects as those of the constituent members shown in FIG. 1 of the first embodiment. In FIG. 4, 1 is a semiconductor laser, 2 is a first photoelectric converter,
3 is a drive current control circuit, 4 is a heating / cooling element, 5 is a temperature control circuit, 10 is a half mirror, 11a is a first optical filter whose pass characteristic monotonically increases as the oscillation wavelength increases, 11
b is a second optical filter whose pass characteristic decreases monotonously, 12 is a second optical-electrical converter, and 15 compares two input electric signals, and when both increase or decrease, the semiconductor laser 1 It is determined that the light intensity of the output light has changed, and in the case of increasing / decreasing operations contradictory to each other, it is determined that the oscillation wavelength of the output light has changed, and the drive current control circuit 3 or the temperature control circuit 5
It is a comparison operation circuit that outputs an electric signal to the.

FIG. 5 is a diagram showing an example of the pass characteristics of the first and second optical filters. In FIG. 5, a is the monotonically increasing pass characteristic of the first optical filter 11a, and b is the second.
3 is a monotonically decreasing pass characteristic of the optical filter 11b.

The operation of the wavelength stabilizing device for the semiconductor laser according to the third embodiment having the above-described structure will be described.
First, the monitor light which is a part of the output light of the semiconductor laser 1 is split into the output light A and the output light B by the half mirror 10. The branched output light A is input to the first optical-electrical converter 2 via the first optical filter 11a, and when the oscillation wavelength is increased, the electric signal E that is output is increased in intensity.
Converted to 1. Further, the branched output light B is input to the second optical-electrical converter 12 via the second optical filter 11b, and is converted into an electric signal E2 in which the output light intensity decreases when the oscillation wavelength increases. To be done.

As a result, when the electric signals E1 and E2 increase or decrease at the same time, the semiconductor laser 1
It is possible to detect that the output light intensity has changed. further,
It can be detected that the oscillation wavelength becomes large when the electric signal E1 increases and the electric signal E2 decreases, and that the oscillation wavelength becomes small when the electric signal E1 decreases and the electric signal E2 increases. Therefore, in the comparison operation circuit 15, an electric signal corresponding to the change of the light intensity is supplied to the drive current control circuit 3 from the change of the inputted electric signals E1 and E2, and an electric signal corresponding to the change of the oscillation wavelength is supplied to the temperature control circuit 5. Output to.

The drive current control circuit 3 supplies a drive current to the semiconductor laser 1 according to the magnitude of the input electric signal. The semiconductor laser 1 outputs an output light having a light intensity according to the drive current. At this time, a feedback loop is formed regarding the control of the light intensity of the output light output from the semiconductor laser 1, and the light intensity can be controlled to be constant.

Further, the temperature control circuit 5 operates the set temperature according to the inputted electric signal. Since the oscillation wavelength of the semiconductor laser 1 changes depending on the temperature, the temperature control circuit 5 controls the heating / cooling element 4 so that the semiconductor laser 1 reaches the set temperature. At this time, a feedback loop is formed with respect to the oscillation wavelength of the semiconductor laser 1, and the oscillation wavelength can be controlled to be constant.

As described above, it is possible to stabilize the oscillation wavelength by detecting the oscillation wavelength component of the semiconductor laser 1 and controlling the feedback loop so as to keep the oscillation wavelength constant.

In the third embodiment, the pass characteristics are such that the first optical filter 11a monotonously increases and the second optical filter 11b monotonically decreases, but it is also possible to have the opposite configuration. There is no end.

[0029]

As described above, according to the present invention,
The oscillation wavelength of the semiconductor laser can be stabilized by detecting the variation in the oscillation wavelength of the output light of the semiconductor laser and feedback controlling the temperature of the semiconductor laser according to the detected variation. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a wavelength stabilization device for a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a pass characteristic of an optical filter.

FIG. 3 is a block diagram showing a configuration of a wavelength stabilization device for a semiconductor laser according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a wavelength stabilization device for a semiconductor laser according to a third embodiment of the present invention.

FIG. 5 is a diagram showing an example of pass characteristics of first and second optical filters.

FIG. 6 is a block diagram showing a configuration of a conventional wavelength stabilization device for a semiconductor laser.

[Explanation of symbols]

1 ... Semiconductor laser, 2 ... First optical-electrical converter, 3
... Drive current control circuit, 4 ... Heating / cooling element, 5 ... Temperature control circuit, 10 ... Half mirror, 11 ... Optical filter,
11a ... 1st optical filter, 11b ... 2nd optical filter, 12 ... 2nd optical-electrical converter, 13 ... Reference power supply,
14, 15 ... Comparison operation circuit.

Claims (3)

[Claims] 1. A semiconductor laser that outputs a signal light and a monitor light as output light having a light intensity and an oscillation wavelength according to a driving current and temperature, and an electric signal having a magnitude according to an input light intensity. 1. photoelectric conversion means, drive current control means for controlling the drive current of the semiconductor laser by an electric signal,
A semiconductor that includes heating / cooling means for heating or cooling the semiconductor laser and temperature control means for controlling an electric signal supplied to the heating / cooling means to keep the temperature constant, and controlling the drive current of the semiconductor laser to be constant. In a wavelength stabilizer for a laser, a branching unit that branches the signal light of the semiconductor laser, an optical selecting unit that has a passage characteristic in which the light intensity changes in accordance with an input oscillation wavelength, and an optical selecting unit that responds to the input light intensity Second photoelectric conversion means for converting into an electric signal of a certain magnitude, a reference power source for outputting a reference electric signal according to a set wavelength, and the first
The electric signal output from the photoelectric conversion means and the electric signal including the change in the oscillation wavelength output from the second photoelectric conversion means via the optical selection means are calculated, and the electric signal is compared with the reference electric signal. A wavelength stabilization device for a semiconductor laser, comprising: a comparison calculation means for outputting an electric signal to the temperature control means to control the temperature of the semiconductor laser to be constant. 2. A semiconductor laser which outputs signal light and monitor light as output light having light intensity and oscillation wavelength according to drive current and temperature, and an electric signal having a magnitude according to input light intensity. 1. photoelectric conversion means, drive current control means for controlling the drive current of the semiconductor laser by an electric signal,
A semiconductor that includes heating / cooling means for heating or cooling the semiconductor laser and temperature control means for controlling an electric signal supplied to the heating / cooling means to keep the temperature constant, and controlling the drive current of the semiconductor laser to be constant. In a laser wavelength stabilizing device, a branching unit that branches the monitor light of the semiconductor laser, an optical selecting unit that has a passing characteristic in which the light intensity changes according to an input oscillation wavelength, and a light selecting unit that receives the input light intensity A second photoelectric conversion means for converting into an electric signal of a certain magnitude, a reference power source for outputting a reference electric signal according to a set wavelength, an electric signal output by the first photoelectric conversion means, and the optical selection means. Then, the electric signal including the variation of the oscillation wavelength output from the second photoelectric conversion means is calculated, and the electric signal corresponding to the comparison with the reference electric signal is output to the temperature control means. An apparatus for stabilizing the wavelength of a semiconductor laser, comprising: an arithmetic means for controlling the temperature of the semiconductor laser to be constant. 3. A semiconductor laser that outputs signal light and monitor light as output light having a light intensity and an oscillation wavelength according to a drive current and temperature, and a drive current control means that controls the drive current of the semiconductor laser by an electric signal. Heating and cooling means for heating or cooling the semiconductor laser, temperature control means for controlling the electric signal supplied to the heating and cooling means to keep the temperature constant, and output light A and output light for monitoring the semiconductor laser. B
Inputting the output light A and the output light B, inputting the output light A and the output light B, and changing the light intensity according to the oscillation wavelength and having contradictory passing characteristics. First, it converts into an electric signal of the magnitude according to the light intensity
The electric signals output from the second photoelectric conversion means and the first and second photoelectric conversion means are compared, and the light intensity changes when both increase and decrease, and the oscillation wavelength changes when both increase and decrease contradict each other. A wavelength of the semiconductor laser, characterized in that it is determined to be a fluctuation, and a comparison calculation means for outputting an electric signal to the drive current control means or the temperature control means is provided, and the drive current and temperature of the semiconductor laser are controlled to be constant. Stabilizer.