JPH09246646A - Semiconductor laser controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to make a semiconductor laser controller for achieving a wide temperature range and the high-speed pulse drive of a semiconductor laser by a method wherein the mean light output of the laser is controlled constant and the deterioration of a signal waveform, which is accompanied with the pulse drive, is compensated. SOLUTION: The voltage of an optical signal detected by a light-receiving element 2 for monitor use is converted into a mean voltage in an APC part 3 and the mean voltage is compared with a reference voltage. The pulsed current value of a semiconductor laser drive part 4 is controlled so that the compared result is zero. Moreover, this optical signal is inputted in a duty ratio control part 5 and the duty ratio of the optical signal is calculated. This calculated value and a reference value is compared with each other, a duty ratio variable part 6 is controlled so that a difference between the calculated value and the reference calue is zero and the duty ratio of a pulse signal, which is inputted in the drive part 4, is changed. Thereby, a fluctuation in a quantum differential efficiency in a semiconductor laser 1 is compensated by a pulse drive current and the generation of the deterioration of an extinction ratio is not caused. Moreover, the duty ratio of the pulse signal is compensated and the deterioration of the pulse waveform of a light output of the laser is prevented from being generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser control device for converting an electric signal into an optical signal in an optical transmission circuit or the like, and more particularly to a semiconductor laser control device for temperature compensation of laser output.

[0002]

2. Description of the Related Art The gain of a semiconductor laser, that is, the ratio of stimulated emission of light in the semiconductor laser becomes lower with respect to the injected carrier density as the temperature rises. On the other hand, since the temperature loss of the optical loss of the semiconductor laser is small, the threshold current density of the semiconductor laser increases as the temperature rises.
Therefore, the optical output / input current characteristics of the semiconductor laser change with temperature changes.

Conventionally, in a semiconductor laser that performs electric / optical conversion in an optical transmission circuit or the like, in order to obtain a constant laser output irrespective of a disturbance such as a temperature change, an automatic laser power is monitored to adjust the driving power. A semiconductor laser control device having a power control (APC) function is generally used.

FIG. 10 shows a conventionally known semiconductor laser control device with an APC function. In FIG. 10, reference numeral 51 is a semiconductor laser, 52 is a light receiving element (photodiode) for monitoring, 53 is an auto power control unit (hereinafter, APC unit), 54 is a semiconductor laser drive unit, and 55.
Indicates a bias current driver (DC current driver), respectively.

In this semiconductor laser control device, a pulse current proportional to a signal input is supplied from the semiconductor laser drive section 54 to the semiconductor laser 51 under a predetermined direct current value from the bias current drive section 55. The semiconductor laser 51 supplied with an electric current outputs an optical output proportional to the electric current value from the reflecting surfaces on both sides. One light output is emitted to the optical fiber 56 as a main beam, and the other light output is input to the monitor light receiving element 52 as a monitor beam.

The monitor light receiving element 52 converts an optical signal into an electric signal. The optical signal detected by the monitor light receiving element 52 is converted into an average voltage by the APC section 53,
It is compared with the reference voltage. The APC section 53 controls the direct current value (bias current value) by the bias current drive section 55 so that the comparison result is always zero.

This semiconductor laser control device is characterized in that it compensates for the deterioration of the electric / optical conversion efficiency of the semiconductor laser due to the ambient temperature and deterioration over time, and keeps the optical average output constant at all times.

[0008]

However, in the conventional semiconductor laser control device as described above, since only the bias current is controlled in order to keep the light average output constant, the pulse current becomes a constant value and the temperature There is a problem that a change in the quantum differential efficiency (current in the laser emission region / optical output conversion efficiency) of the semiconductor laser due to the change appears in the optical output as a change in the extinction ratio (on / off ratio of the pulse signal). In the high temperature region, the extinction ratio deteriorates due to the deterioration of the quantum differential efficiency, resulting in S / N deterioration, and in the low temperature region, on the contrary, the bias current becomes too small, which is significantly smaller than the oscillation threshold of the semiconductor laser. Become.

Therefore, the time during which the semiconductor laser oscillates becomes long, the oscillation time when the pulse current is on becomes short, and the pulse waveform of the optical output deteriorates. For this reason, it is becoming difficult for conventional devices to cope with the trend of expanding ambient temperature conditions and increasing the speed of pulse signals.

The present invention has been made by paying attention to the above-mentioned problems in the conventional semiconductor laser control device, and it controls the optical average output to be constant and compensates for the deterioration of the signal waveform due to the pulse driving. By doing so, it is an object to obtain a semiconductor laser control device that is compatible with a wide temperature range and high-speed pulse driving.

[0011]

In order to achieve the above-mentioned object, a semiconductor laser control device according to the present invention comprises a laser drive unit for supplying a pulse signal corresponding to an input signal to a semiconductor laser as a pulse current, and the semiconductor drive device. A monitor light receiving element that converts the optical output from the laser into an electric signal and an electric signal of the monitor light receiving element are input to calculate an average optical output, and the laser drive is performed so that the average optical output becomes a constant value. An auto power control unit for controlling the unit, a duty ratio variable unit for variably adjusting the duty ratio of the pulse signal sent to the laser drive unit, and a duty ratio of the electric signal output by the monitor light receiving element, And a duty ratio control means for controlling the duty ratio varying unit so that the duty ratio becomes a constant value.

In the semiconductor laser control device according to the present invention, the average power output of the semiconductor laser becomes a constant value by controlling the laser drive section by the auto power control means, and the duty ratio control means controls the duty ratio variable section. By doing so, the semiconductor laser is driven so that the duty ratio of the optical output becomes a constant value. Thereby, the deterioration of the signal waveform due to the pulse driving is compensated.

According to another aspect of the invention, there is provided a semiconductor laser control device in which a laser drive unit for supplying a pulse signal corresponding to an input signal to the semiconductor laser as a pulse current, and a monitor light receiving unit for converting an optical output from the semiconductor laser into an electric signal. Element and an automatic power control means for inputting an electric signal of the light receiving element for monitoring to calculate an average optical output and controlling the laser driving section so that the average optical output has a constant value, and the semiconductor laser. A duty ratio control means for calculating a duty ratio of a bias current drive unit for controlling a bias current and an electric signal output by the monitor light receiving element, and controlling the bias current drive unit so that the duty ratio becomes a constant value. And is equipped with.

In the semiconductor laser control device according to the present invention, the average power output of the semiconductor laser becomes a constant value by controlling the laser drive section by the auto power control means, and the duty ratio control means controls the bias current drive section. By doing so, the semiconductor laser is driven so that the duty ratio of the optical output becomes a constant value. Thereby, the deterioration of the signal waveform due to the pulse driving is compensated.

A semiconductor laser control device according to the next invention has a bias current drive section for controlling a bias current of the semiconductor laser, and the duty ratio control means comprises a duty ratio of an electric signal output from the monitor light receiving element. Is calculated and the duty ratio variable unit is controlled so that the duty ratio becomes a constant value, and the bias current drive unit is controlled so that the duty ratio becomes a constant value.

In the semiconductor laser control device according to the present invention, the average power output of the semiconductor laser becomes a constant value by controlling the laser drive section by the auto power control means, and the duty ratio control means makes the duty ratio variable section and the bias. By controlling the current driver, the semiconductor laser is driven so that the duty ratio of the light output becomes a constant value. Thereby, the deterioration of the signal waveform due to the pulse driving is compensated.

A semiconductor laser control apparatus according to the next invention is a laser drive unit for supplying a pulse signal corresponding to an input signal to the semiconductor laser as a pulse current, and a monitor light receiving unit for converting an optical output from the semiconductor laser into an electric signal. Element and an automatic power control means for inputting an electric signal of the monitor light receiving element to calculate an average optical output and controlling the laser driving section so that the average optical output becomes a constant value, and the laser driving section. A duty ratio variable unit that variably adjusts the duty ratio of the pulse signal to be sent to, and a comparison circuit that outputs a difference signal by comparing the duty ratio of the pulse signal and the duty ratio of the electrical signal of the monitor light receiving element, And a duty ratio control means for controlling the duty ratio variable unit so that the difference value output from the comparison circuit becomes zero. Than it is.

In the semiconductor laser controller according to the present invention, the average power output of the semiconductor laser becomes a constant value by controlling the laser drive section by the auto power control means, and the duty ratio control means controls the duty ratio variable section. By doing so, the semiconductor laser is driven so that the duty ratio of the optical output is synchronized with the duty ratio of the pulse signal corresponding to the input signal.

A semiconductor laser control apparatus according to the next invention has an analog / digital signal converting means for converting an electric signal level of the monitor light receiving element into a digital signal, and the duty ratio variable section is faster than the pulse signal. The duty ratio control means controls the number of shift register stages in the duty ratio variable section from the digital signal to perform variable control of the duty ratio, including a shift register operated by the clock signal output from the clock generation means.

In the semiconductor laser control device according to the present invention, the electric signal level of the monitor light receiving element is converted into a digital signal by the analog / digital signal conversion means, and the duty ratio control means is used by the digital signal to shift register in the duty ratio variable section. The number of stages is controlled and the duty ratio is variably controlled digitally.

A semiconductor laser control device according to the next invention has an analog / digital signal conversion means for converting the difference value signal output from the comparison circuit into a digital signal, and the duty ratio variable section is faster than the pulse signal. The duty ratio control means controls the number of shift register stages in the duty ratio variable section from the digital signal to perform variable control of the duty ratio, including a shift register operated by the clock signal output from the clock generation means.

In the semiconductor laser control device according to the present invention, the difference value signal output from the comparison circuit is converted into a digital signal by the analog / digital signal converting means,
The duty ratio control means controls the number of shift register stages in the duty ratio variable section by the digital signal to digitally perform variable control of the duty ratio.

A semiconductor laser control device according to the next invention has a duty ratio amplifying unit in front of the duty ratio changing unit.

In the semiconductor laser control device according to the present invention, the pulse signal input to the duty ratio varying unit is amplified by the duty ratio amplifying unit.

In the semiconductor laser control device according to the next invention, a bias current driver for controlling the bias current of the semiconductor laser to a constant value in order to output continuous output light, and continuous output light from the semiconductor laser into an electric signal. An auto power control means for inputting the monitor light receiving element to be converted and the electric signals of the monitor light receiving element to calculate an average optical output, and controlling the bias current drive unit so that the average optical output becomes a constant value. And an external modulator that turns on / off the continuous output light sent from the semiconductor laser by a pulse signal and converts the continuous output light into pulse light, and outputs a pulse signal corresponding to the input signal of the external modulator. An external modulator driving unit, a branching unit for branching the pulsed light converted by the external modulator for monitor output, and the branching unit. By inputting pulsed light of the monitor output that has been diversified, an external monitor light receiving element that converts the pulsed light into an electrical signal and a duty ratio of the electrical signal output by the electrical signal of the external monitor light receiving element are calculated And a duty ratio control means for controlling the external modulator driving unit so that the duty ratio becomes a constant value.

In the semiconductor laser control device according to the present invention, the bias current drive section is controlled by the auto power control means so that the optical output of the semiconductor laser becomes a constant value, and the optical output of the semiconductor laser is controlled by the external modulator by the external modulator drive section. It is converted into pulsed light according to the pulse signal from. The duty ratio control means controls the external modulator driving section, so that the duty ratio of the pulsed light becomes a constant value.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 shows Embodiment 1 of a semiconductor laser control apparatus according to the present invention. In FIG. 1, 1
Is a semiconductor laser, 2 is a light receiving element (photodiode) for monitoring, 3 is an APC unit, 4 is a semiconductor laser drive unit, 5 is a duty ratio control unit, and 6 is a duty ratio variable unit.

The monitor light-receiving element 2 converts the optical output from the semiconductor laser 1 into an electric signal and outputs this electric signal (monitor output) to the APC section 3 and the duty ratio control section 5.

The APC section 3 receives an electric signal from the monitor light receiving element 2 to calculate an average optical output, and controls the semiconductor laser driving section 4 so that the average optical output becomes a constant value.

The semiconductor laser drive section 4 supplies a pulse signal to the semiconductor laser 1 as a pulse current,
The pulse current value is controlled by the APC unit 3.

The duty ratio control unit 5 calculates the duty ratio of the electric signal from the monitor light receiving element 2 and controls the duty ratio variable unit 6 so that the duty ratio becomes a constant value.

The duty ratio changing unit 6 changes the duty ratio of the pulse signal according to the instruction from the duty ratio control unit 5, and keeps the duty ratio at a constant value.

Next, the operation of the first embodiment will be described.

A pulse current proportional to the input signal is supplied to the semiconductor laser driving unit 4 via the duty ratio changing unit 6. This pulse signal is converted into a current by the semiconductor laser drive unit 4 and supplied to the semiconductor laser 1. When the semiconductor laser 1 is supplied with a current from the semiconductor laser drive unit 4, the semiconductor laser 1 outputs an optical output proportional to the current value from the reflecting surfaces on both sides. One light output is emitted to the optical fiber 19 as a main beam, and the other light is input to the monitor light receiving element 2 as a monitor beam and converted into an electric signal.

The optical signal detected by the monitor light receiving element 2 is converted into an average voltage by the APC section 3 and compared with the reference voltage. The APC unit 3 controls the pulse current value of the semiconductor laser driving unit 4 so that the comparison result is always zero.

The optical signal detected by the monitor light receiving element 2 is also input to the duty ratio control section 5, and the duty ratio control section 5 calculates the duty ratio.
The duty ratio control unit 5 compares the calculated value with a preset reference value, controls the duty ratio variable unit 6 so that the difference becomes zero, and controls the duty ratio of the pulse signal input to the semiconductor laser driving unit 4. Change the duty ratio.

As a result, the fluctuation of the quantum differential efficiency in the semiconductor laser 1 is compensated by the pulse drive current value, and the extinction ratio does not deteriorate. Further, the duty ratio is compensated, and the deterioration of the pulse waveform of the optical output is avoided.

In this semiconductor laser control device, since bias driving is unnecessary, adjustment is facilitated and individual differences of semiconductor lasers are easily absorbed. Further, since the circuit configuration can be made relatively simple, it becomes suitable not only for an optical communication device but also for a semiconductor laser driving unit of a laser printer or the like for increasing speed and definition.

(Second Embodiment) FIG. 2 shows a second embodiment of the semiconductor laser control device according to the present invention. still,
2, parts corresponding to those in FIG. 1 are designated by the same reference numerals as those in FIG. 1 and their description is omitted.

In this embodiment, a duty ratio amplifying unit 7 including a delay line 8 and an OR element 9 is provided in front of the duty ratio varying unit 6, and the duty ratio varying unit 6 is provided.
A pulse signal whose duty ratio width is amplified by the duty ratio amplifier 7 is input to the input signal.

Next, the operation of the second embodiment will be described.

The pulse signal whose duty ratio width is amplified with respect to the input signal by the duty ratio amplifying unit 7 is input to the duty ratio varying unit 6 and the duty ratio is controlled.

This pulse signal is applied to the semiconductor laser driving unit 4
Is converted into a current and supplied to the semiconductor laser 1. Semiconductor laser 1 supplied with current from the semiconductor laser drive unit 4
Emits a light output proportional to the current value from the reflecting surfaces on both sides. One light output is emitted to the optical fiber 19 as a main beam, and the other light is input to the monitor light receiving element 2 as a monitor beam and converted into an electric signal.

The optical signal detected by the monitor light receiving element 2 is converted into an average voltage by the APC section 3 and compared with the reference voltage. The APC unit 3 controls the pulse current value of the semiconductor laser driving unit 4 so that the comparison result is always zero.

The optical signal detected by the monitor light receiving element 2 is also input to the duty ratio control section 5, and the duty ratio control section 5 calculates the duty ratio.
The duty ratio control unit 5 compares the calculated value with a preset reference value, controls the duty ratio variable unit 6 so that the difference becomes zero, and controls the duty ratio of the pulse signal input to the semiconductor laser driving unit 4. Change the duty ratio.

In this semiconductor laser control device, the same effects as those of the semiconductor laser control device in the first embodiment are obtained, and the duty ratio amplifying section 7 is added, so that the semiconductor laser control device has a wide duty ratio variable range. Will be able to.

(Third Embodiment) FIG. 3 shows a semiconductor laser control apparatus according to a third embodiment of the present invention. still,
Also in FIG. 3, the portions corresponding to those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and the description thereof will be omitted.

In this embodiment, a bias current drive unit (DC current drive unit) 10 for controlling the bias current of the semiconductor laser 1 is provided in place of the duty ratio variable unit.

The duty ratio control unit 5 calculates the duty ratio of the electric signal from the monitor light receiving element 2, compares the calculated value with a preset reference value, and bias current so that the difference becomes zero. The drive unit 10 is controlled.

Next, the operation of the third embodiment will be described.

A pulse current proportional to the input signal is supplied to the semiconductor laser driving section 4. This pulse signal is converted into a current by the semiconductor laser drive unit 4 and supplied to the semiconductor laser 1. The semiconductor laser 1 includes a semiconductor laser drive unit 4
By being supplied with more current, an optical output proportional to the current value is sent out from the reflecting surfaces on both sides. One light output is emitted to the optical fiber 19 as a main beam, and the other light is
The light is input to the light receiving element 2 for monitoring as a monitor beam and converted into an electric signal.

The optical signal detected by the monitor light receiving element 2 is converted into an average voltage by the APC section 3 and compared with the reference voltage. The APC unit 3 controls the pulse current value of the semiconductor laser driving unit 4 so that the comparison result is always zero.

The optical signal detected by the monitor light receiving element 2 is also input to the duty ratio control section 5, and the duty ratio control section 5 calculates the duty ratio.
The duty ratio controller 5 compares the calculated value with a preset reference value, controls the bias current driver 10 so that the difference becomes zero, and controls the bias current value supplied to the semiconductor laser 1. . This sets the bias point to the threshold value.

In this semiconductor laser control device, the same effects as those of the semiconductor laser control device in the first embodiment can be obtained, and since the bias point can always be set to the threshold value, it can be adapted to higher speed signal transmission. .

(Fourth Embodiment) FIG. 4 shows a fourth embodiment of the semiconductor laser control apparatus according to the present invention. still,
In FIG. 4, portions corresponding to FIGS. 1 and 3 are shown in FIGS.
The same reference numerals are given to the same reference numerals, and the description is omitted.

This embodiment is a combination of the above-described first and third embodiments, and includes a duty ratio control unit 5
Compares the calculated value of the duty ratio of the electric signal from the monitor light receiving element 2 with a preset reference value, and controls the duty ratio variable unit 6 so that the difference becomes zero.
The bias current driver 10 compares the calculated value of the duty ratio with a preset reference value so that the difference becomes zero.
Control.

Next, the operation of the fourth embodiment will be described.

A pulse current proportional to the input signal is supplied to the semiconductor laser driving section 4. This pulse signal is converted into a current by the semiconductor laser drive unit 4 and supplied to the semiconductor laser 1. The semiconductor laser 1 includes a semiconductor laser drive unit 4
By being supplied with more current, an optical output proportional to the current value is sent out from the reflecting surfaces on both sides. One light output is emitted to the optical fiber 19 as a main beam, and the other light is
The light is input to the light receiving element 2 for monitoring as a monitor beam and converted into an electric signal.

The optical signal detected by the monitor light receiving element 2 is converted into an average voltage by the APC section 3 and compared with the reference voltage. The APC unit 3 controls the pulse current value of the semiconductor laser driving unit 4 so that the comparison result is always zero.

The optical signal detected by the monitor light receiving element 2 is also input to the duty ratio control section 5, and the duty ratio control section 5 calculates the duty ratio.
The duty ratio control unit 5 compares the calculated value with a preset reference value, controls the duty ratio variable unit 6 so that the difference becomes zero, and controls the duty ratio of the pulse signal input to the semiconductor laser driving unit 4. Change the duty ratio. Further, the duty ratio controller 5 simultaneously controls the bias current driver 10 to control the value of the bias current supplied to the semiconductor laser 1.

In this semiconductor laser control device, not only the bias current control but also the duty ratio control is performed, so that not only the semiconductor laser but also the frequency characteristic of the laser drive section can be compensated, and therefore highly accurate adjustment is possible. Therefore, the control device becomes more stable.

In this embodiment also, the second embodiment is used.
The duty ratio amplifying unit 7 may be provided in front of the duty ratio changing unit 6.

(Fifth Embodiment) FIG. 5 shows a semiconductor laser control apparatus according to a fifth embodiment of the present invention. still,
5, parts corresponding to those in FIG. 1 are designated by the same reference numerals as those in FIG. 1 and their description is omitted.

In this embodiment, the comparison circuit 11 is provided. The comparison circuit 11 inputs an electric signal from the monitor light receiving element 2 and a pulse current proportional to the input signal, and the duty ratio of the optical signal detected by the monitor light receiving element 2 and the pulse current duty proportional to the input signal. The ratio is compared and the difference signal is output to the duty ratio controller 5. The duty ratio control unit 5 controls the duty ratio variable unit 6 so that the output difference value becomes zero.

Next, the operation of the fifth embodiment will be described.

A pulse current proportional to the input signal is supplied to the semiconductor laser driving section 4. This pulse signal is converted into a current by the semiconductor laser drive unit 4 and supplied to the semiconductor laser 1. The semiconductor laser 1 includes a semiconductor laser drive unit 4
By being supplied with more current, an optical output proportional to the current value is sent out from the reflecting surfaces on both sides. One light output is emitted to the optical fiber 19 as a main beam, and the other light is
The light is input to the light receiving element 2 for monitoring as a monitor beam and converted into an electric signal.

The optical signal detected by the monitor light receiving element 2 is converted into an average voltage by the APC section 3 and compared with the reference voltage. The APC unit 3 controls the pulse current value of the semiconductor laser driving unit 4 so that the comparison result is always zero.

The optical signal detected by the monitor light receiving element 2 is also input to the comparison circuit 11. Comparison circuit 1
Reference numeral 1 denotes an electric signal input from the monitor light receiving element 2 and a pulse current proportional to the input signal, and a duty ratio of the optical signal detected by the monitor light receiving element 2 and a duty ratio of the pulse current proportional to the input signal. And outputs a difference signal to the duty ratio control unit 5, and the duty ratio control unit 5 controls the duty ratio variable unit 6 so that the output difference value from the comparison circuit 11 becomes zero to drive the semiconductor laser. The duty ratio of the pulse signal input to the unit 4 is changed.

In this semiconductor laser control device, the same effects as those of the semiconductor laser control device in the first embodiment can be obtained, and the duty ratio control unit 6 can be made adjustment-free. In addition, the device can be converted into an optical signal in the same circuit regardless of the speed of the input signal, which makes the device highly versatile.

In this embodiment also, the second embodiment is used.
As described above, the duty ratio amplifying unit 7 can be installed in front of the duty ratio changing unit 6.

(Sixth Embodiment) FIG. 6 shows a sixth embodiment of the semiconductor laser control apparatus according to the present invention. still,
6, parts corresponding to those in FIG. 1 are designated by the same reference numerals as those in FIG. 1 and their description is omitted.

In this embodiment, an analog / digital converter 12 and a high speed clock generator 13 are provided.

The analog / digital converter 12 converts the output electric signal level of the monitor light receiving element 2 into a digital signal, and inputs the digital signal to the duty ratio controller 5.

The duty ratio controller 5 compares the digital value of the digital signal from the analog / digital converter 12 with a preset reference value, and the high-speed clock generator 13 causes the duty ratio to be zero so that the difference becomes zero. Variable part 6
The number of shift register stages is controlled by using the clock signal input to.

The duty ratio varying unit 6 inputs a clock signal, which is sufficiently faster than the pulse signal proportional to the input signal, from the high speed clock generating unit 13, controls the number of shift register stages using this clock signal, and drives the semiconductor laser driving unit. The duty ratio of the pulse signal input to 4 is variably set.

As shown in FIG. 7, the duty ratio variable section 6 includes a shift register 14 and an OR element 15.
The duty ratio controller 5 controls the number of delay stages of the shift register 14, and the shift register 14 delays the input signal using the high-speed clock signal from the high-speed clock generator 13. The duty ratio is increased by synthesizing the delay signal and the input signal by the OR element 15.

Next, the operation of the sixth embodiment will be described.

A pulse current proportional to the input signal is supplied to the semiconductor laser driving section 4. This pulse signal is converted into a current by the semiconductor laser drive unit 4 and supplied to the semiconductor laser 1. The semiconductor laser 1 includes a semiconductor laser drive unit 4
By being supplied with more current, an optical output proportional to the current value is sent out from the reflecting surfaces on both sides. One light output is emitted to the optical fiber 19 as a main beam, and the other light is
The light is input to the light receiving element 2 for monitoring as a monitor beam and converted into an electric signal.

The optical signal detected by the monitor light receiving element 2 is converted into an average voltage by the APC section 3 and compared with the reference voltage. The APC unit 3 controls the pulse current value of the semiconductor laser driving unit 4 so that the comparison result is always zero.

The optical signal detected by the monitor light receiving element 2 is also input to the analog / digital converter 12, and the analog / digital converter 12 outputs the duty ratio of the optical signal as a digital signal. The duty ratio control unit 5 compares the digital signal value with a preset reference value, and uses the clock signal input from the high speed clock generation unit 13 to the duty ratio variable unit 6 so that the difference becomes zero. The number of shift register stages is controlled to change the duty ratio of the pulse signal input to the semiconductor laser drive unit 4.

In this semiconductor laser control device, the same effect as that of the semiconductor laser control device in the first embodiment is obtained, and the duty ratio control is performed by digital control. Therefore, for example, the optical transmission of the semiconductor laser by this device is performed. It becomes possible to perform control using a CPU that is frequently used in a communication device in which a container is mounted, and it is possible to make the device highly versatile.

In this embodiment also, the second embodiment is used.
As described above, the duty ratio amplifying unit 7 can be installed in front of the duty ratio changing unit 6.

(Seventh Embodiment) FIG. 8 shows a seventh embodiment of the semiconductor laser control apparatus according to the present invention. still,
In FIG. 8, parts corresponding to FIGS. 5 and 6 are shown in FIGS.
The same reference numerals are given to the same reference numerals, and the description is omitted.

This embodiment is a combination of the fifth and sixth embodiments, in which the comparator circuit 11 inputs an electric signal from the monitor light receiving element 2 and also inputs a pulse current proportional to the input signal to receive the monitor light. The duty ratio of the optical signal detected by the element 2 is compared with the duty ratio of the pulse current proportional to the input signal, and the difference signal is output to the analog / digital converter 12.

The analog / digital converter 12 outputs the output difference value from the comparator 11 as a digital signal to the duty ratio controller 5.

The duty ratio control unit 5 uses the clock signal input to the duty ratio variable unit 6 from the high speed clock generation unit 13 so that the digital signal value from the analog / digital conversion unit 12 shows zero. To control.

Next, the operation of the seventh embodiment will be described.

A pulse current proportional to the input signal is supplied to the semiconductor laser driving section 4. This pulse signal is converted into a current by the semiconductor laser drive unit 4 and supplied to the semiconductor laser 1. The semiconductor laser 1 includes a semiconductor laser drive unit 4
By being supplied with more current, an optical output proportional to the current value is sent out from the reflecting surfaces on both sides. One light output is emitted to the optical fiber 19 as a main beam, and the other light is input to the monitor light receiving element 2 as a monitor beam and converted into an electric signal.

The optical signal detected by the monitor light receiving element 2 is converted into an average voltage by the APC section 3 and compared with the reference voltage. The APC unit 3 controls the pulse current value of the semiconductor laser driving unit 4 so that the comparison result is always zero.

The optical signal detected by the monitor light receiving element 2 is also input to the comparison circuit 11. Comparison circuit 1
Reference numeral 1 denotes an electric signal input from the monitor light receiving element 2 and a pulse current proportional to the input signal, and a duty ratio of the optical signal detected by the monitor light receiving element 2 and a duty ratio of the pulse current proportional to the input signal. And the difference signal is output to the analog / digital conversion unit 12.

This output difference value is input as a digital signal from the analog / digital conversion unit 12 to the duty ratio control unit 5, and the duty ratio control unit 5 outputs the duty ratio from the high speed clock generation unit 13 so that the digital signal value shows zero. The number of shift register stages using the clock signal input to the ratio variable unit 6 is controlled. As a result, the duty ratio varying unit 6 variably sets the duty ratio of the pulse signal input to the semiconductor laser driving unit 4.

In this semiconductor laser control device, the same effect as that of the semiconductor laser control device in the first embodiment is obtained, and the duty ratio control is changed to digital control as in the semiconductor laser control device in the sixth embodiment. By doing so, it becomes possible to control using a CPU that is frequently used in a communication device in which an optical transmitter of a semiconductor laser according to the present device is mounted, and it becomes a highly versatile device, and an input signal is compared by a comparison circuit. By inputting it as a reference value, it can be converted into an optical signal in the same circuit regardless of the speed of the input signal, which also makes the device highly versatile.

In this embodiment also, the second embodiment is used.
As described above, the duty ratio amplifying unit 7 can be installed in front of the duty ratio changing unit 6.

(Embodiment 8) FIG. 9 shows an embodiment 8 of the semiconductor laser control device according to the present invention. still,
9, parts corresponding to those in FIGS. 1 and 3 are shown in FIGS.
The same reference numerals are given to the same reference numerals, and the description is omitted.

In this embodiment, the semiconductor laser 1 is
Bias current driver 10 controlled by APC unit 3
The continuous output light (CW (continuou
s wave) Light) is output.

The external modulator 17 inputs the main beam of the semiconductor laser 1 through the optical fiber 16, receives the pulse voltage control from the external modulator driving section 22, and turns on / off the CW light by the pulse signal to output the CW light. Convert to pulsed light.

This pulsed light is sent to the optical fiber 18 and input to the optical coupler 21 as a branching means. The optical coupler 21 splits the pulsed light for monitor output and sends the pulsed light to both the optical fibers 19 and 20.

The pulsed light output to the optical fiber 20 as a monitor is sent to the external monitor light-receiving element 23, which converts the pulsed light into an electric signal.

The duty ratio controller 5 inputs an electric signal from the external monitor light receiving element 23, calculates the duty ratio of the pulsed light (monitor output), compares the calculated value with a preset reference value, The external modulator driving unit 22 is controlled so that the difference becomes zero.

Next, the operation of the eighth embodiment will be described.

The semiconductor laser 1 has a bias current driver 10
CW light is emitted by applying more bias current,
CW light is sent out from the reflecting surfaces on both sides. One CW light is emitted to the optical fiber 16 as a main beam, and the other CW light is input to the monitor light receiving element 2 as a monitor beam,
Converted to electrical signals. The optical signal detected by the monitor light receiving element 2 is converted into a voltage value by the APC unit 3 and compared with a reference voltage, and the DC current value of the bias current drive unit 10 is always zero so that the comparison result is always zero. Controlled by 3.

CW transmitted from the optical fiber 16
The light is input to the external modulator 17. The external modulator 17 receives pulse voltage control from the external modulator driving unit 22 and converts CW light into pulsed light. This pulsed light is transmitted through the optical fiber 18
Is inputted to the optical coupler 20 via the optical coupler 20, branched by the optical coupler 20, and sent to the optical fiber 19 for communication and the optical fiber 20 for monitor input.

The pulsed light sent to the optical fiber 20 is input to the external monitor light receiving element 23, and converted into an electric signal by the external monitor light receiving element 23. The electric signal output from the external monitor light receiving element 23 is input to the duty ratio control unit 5, and the duty ratio control unit 5 calculates the duty ratio of the electric signal, and the calculated value and a preset reference value are used. And the external modulator driving unit 22 is controlled so that the difference becomes zero, and the duty ratio of the pulse signal input to the external modulator 17 is variably set.

In this semiconductor laser control device, the same effect as that of the semiconductor laser control device in the first embodiment can be obtained in the drive device using the external modulator, and the external modulation can be performed similarly to the deterioration of the differential efficiency of the semiconductor laser. It is possible to prevent the deterioration of the pulse driving ability due to the temperature of the container.
This control device is a control device suitable for an ultra-high-speed transmission (Gb / s-) device.

[0105]

As is apparent from the above description, in the semiconductor laser control device according to the present invention, the deterioration of the pulse waveform of the optical output is avoided as the ambient temperature condition is expanded and the pulse signal speed is increased. Further, in this semiconductor laser control device, since bias driving is unnecessary, adjustment is facilitated and individual differences of semiconductor lasers are easily absorbed, and since the circuit configuration is relatively simple, not only the optical communication device but also the laser The semiconductor laser driving unit of a printer or the like is suitable for high speed and high definition.

In the semiconductor laser control device according to the next invention, the deterioration of the pulse waveform of the optical output is avoided with the expansion of the ambient temperature condition and the speeding up of the pulse signal, and the duty ratio amplifying section is added. It becomes possible to have a wide duty ratio variable range.

In the semiconductor laser control device according to the next invention, the deterioration of the pulse waveform of the optical output is avoided with the expansion of the ambient temperature condition and the speeding up of the pulse signal, and the bias point can always be set to the threshold value. Can adapt to higher speed signal transmission.

In the semiconductor laser control device according to the next invention, the deterioration of the pulse waveform of the optical output is avoided with the expansion of the ambient temperature condition and the speeding up of the pulse signal, and the duty ratio control is performed in addition to the bias current control. Therefore, not only the semiconductor laser but also the frequency characteristic of the laser driving unit can be compensated, highly accurate adjustment is possible, and the control device becomes more stable.

In the semiconductor laser control device according to the next invention, the deterioration of the pulse waveform of the optical output is avoided due to the expansion of the ambient temperature condition and the speeding up of the pulse signal, and the input signal is input as the comparison reference value of the comparison circuit. by doing,
The duty ratio control section can be made non-adjustable, and an optical signal can be converted into an optical signal by the same circuit regardless of the speed of the input signal, resulting in a highly versatile device.

In the semiconductor laser control device according to the next invention, the deterioration of the pulse waveform of the optical output is avoided due to the expansion of the ambient temperature condition and the speeding up of the pulse signal, and the duty ratio control is performed by digital control. The control using the CPU, which is frequently used in the communication device in which the optical transmitter of the semiconductor laser according to the present device is mounted, becomes possible, and the device has high versatility.

In the semiconductor laser control device according to the next invention, the deterioration of the pulse waveform of the optical output is avoided with the expansion of the ambient temperature condition and the speeding up of the pulse signal, and the duty ratio control is digitally controlled. This device enables control using a CPU that is frequently used in a communication device in which an optical transmitter of a semiconductor laser is mounted, and has a high versatility, and an input signal is input as a comparison reference value of a comparison circuit. By doing so, an optical signal can be converted by the same circuit regardless of the speed of the input signal, which also makes the device highly versatile.

In the semiconductor laser control device according to the next invention, the deterioration of the pulse waveform of the optical output is avoided as the ambient temperature condition is widened and the pulse signal is sped up. It is possible to prevent the deterioration of the pulse driving capability due to the temperature of the modulator, and it is suitable for an ultra-high speed transmission (Gb / s ~) device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a semiconductor laser control device according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of a semiconductor laser control device according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of a semiconductor laser control device according to the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of a semiconductor laser control device according to the present invention.

FIG. 5 is a block diagram showing a fifth embodiment of a semiconductor laser control device according to the present invention.

FIG. 6 is a block diagram showing a sixth embodiment of a semiconductor laser control device according to the present invention.

FIG. 7 is a block diagram showing a specific example of a duty ratio variable unit used in the semiconductor laser control device of the sixth embodiment.

FIG. 8 is a block diagram showing a seventh embodiment of a semiconductor laser control device according to the present invention.

FIG. 9 is a block diagram showing an eighth embodiment of a semiconductor laser control device according to the present invention.

FIG. 10 is a block diagram showing a conventional example of a semiconductor laser control device.

[Explanation of symbols]

1 semiconductor laser, 2 monitor light receiving element, 3 APC
Section, 4 semiconductor laser drive section, 5 duty ratio control section, 6 duty ratio variable section, 7 duty ratio amplification section, 8 delay line, 9 OR element, 10 bias current drive section, 11 comparison circuit, 12 analog / digital conversion Section, 13 high-speed clock generation section, 14 shift register, 15 OR element, 16 optical fiber, 17 external modulator, 18, 19, 20 optical fiber, 21 optical coupler, 22 external modulator driving section, 23 external monitor light receiving element

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04B 10/06

Claims (8)

[Claims] 1. A laser drive section for supplying a pulse signal corresponding to an input signal to a semiconductor laser as a pulse current, a monitor light receiving element for converting an optical output from the semiconductor laser into an electric signal, and the monitor light receiving element. Of the pulse signal sent to the laser drive unit, and an automatic power control means for controlling the laser drive unit so that the average light output is a constant value A duty ratio variable unit for variably adjusting the duty ratio, and a duty ratio control unit for calculating the duty ratio of the electric signal output from the monitor light receiving element and controlling the duty ratio variable unit so that the duty ratio becomes a constant value. A semiconductor laser control device comprising: 2. A laser drive unit for supplying a pulse signal corresponding to an input signal to a semiconductor laser as a pulse current, a monitor light receiving element for converting an optical output from the semiconductor laser into an electric signal, and the monitor light receiving element. Of the electric signal, calculates an average optical output, and controls the laser driving unit so that the average optical output has a constant value, and an automatic power control unit that controls a bias current of the semiconductor laser. And a duty ratio control means for calculating the duty ratio of the electric signal output by the monitor light receiving element and controlling the bias current drive unit so that the duty ratio becomes a constant value. And a semiconductor laser control device. 3. A bias current drive unit for controlling a bias current of the semiconductor laser, wherein the duty ratio control means calculates a duty ratio of an electric signal output from the monitor light receiving element, and the duty ratio is 2. The semiconductor laser control device according to claim 1, wherein the duty ratio variable unit is controlled to have a constant value, and the bias current drive unit is controlled so that the duty ratio has a constant value. 4. A laser drive section for supplying a pulse signal corresponding to an input signal to a semiconductor laser as a pulse current, a monitor light receiving element for converting an optical output from the semiconductor laser into an electric signal, and the monitor light receiving element. Of the pulse signal sent to the laser drive unit, and an automatic power control means for controlling the laser drive unit so that the average light output is a constant value A duty ratio variable unit that variably adjusts the duty ratio of the pulse signal, a comparison circuit that outputs a difference signal by comparing the duty ratio of the pulse signal and the duty ratio of the electric signal of the monitor light receiving element, and a difference value output by the comparison circuit. And a duty ratio control means for controlling the duty ratio varying unit so that the duty ratio becomes zero. Place. 5. An analog / digital signal converting means for converting an electric signal level of the monitor light receiving element into a digital signal, wherein the duty ratio variable portion is a clock signal output from a clock generating means faster than the pulse signal. 4. The duty ratio control means controls the number of shift register stages in the duty ratio varying unit from the digital signal to perform variable control of the duty ratio, the shift register operating according to claim 1. Semiconductor laser controller. 6. An analog / digital signal conversion means for converting the difference value signal output from the comparison circuit into a digital signal, wherein the duty ratio variable part is a clock signal output from a clock generation means faster than the pulse signal. 5. The semiconductor according to claim 4, wherein the duty ratio control means controls the number of shift register stages in the duty ratio varying section from the digital signal to perform variable control of the duty ratio. Laser control device. 7. The duty ratio amplifying unit is provided before the duty ratio varying unit.
7. The semiconductor laser control device according to any one of 3, 4, 5, and 6. 8. A bias current drive unit for controlling a bias current of a semiconductor laser to a constant value for outputting continuous output light, and a monitor light receiving element for converting continuous output light from the semiconductor laser into an electric signal. An automatic power control means for inputting an electrical signal of the monitor light-receiving element to calculate an average optical output and controlling the bias current drive unit so that the average optical output has a constant value, and the semiconductor laser outputs An external modulator that turns on / off the continuous output light with a pulse signal to convert the continuous output light into a pulsed light; and an external modulator driving unit that outputs a pulse signal corresponding to the input signal of the external modulator, Branching means for branching the pulsed light converted by the external modulator for monitor output, and inputting pulsed light of the monitor output branched by the branching means Then, the duty ratio of the external monitor light receiving element that converts the pulsed light into an electrical signal and the electrical signal output by the electrical signal of the external monitor light receiving element is calculated, and the duty ratio becomes a constant value. A semiconductor laser control device comprising: a duty ratio control unit that controls an external modulator driving unit.