JPH04115583A - Semiconductor laser drive device - Google Patents

Abstract

PURPOSE:To make it possible to shorten control time of optical output by allowing a duty compensation circuit to make up for duty change in optical output waveform. CONSTITUTION:When a semiconductor laser 1 is actuated, its output state is monitored by a photodiode 4 where the output waveform of the photodiode 4 is adapted to enter a duty compensation circuit 6. Therefore, the compensation circuit 6 controls a pulse drive circuit 3 and drives a semiconductor laser 1 so that it may adjust the duty of optical output waveforms. During this operation, an automatic output power control circuit 5 (APC circuit) is subject to the output of the photodiode 4 and controls the pulse drive circuit 3 so as to make constant the optical output. This construction makes it possible to cut down control items by driving the semiconductor laser only by means of the pulse drive circuit and provide stabilized optical output constantly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor laser active device for driving a semiconductor laser, which is used in optical transmission circuits of electronic equipment and communication equipment.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional semiconductor laser driving device. In the figure, 1 is a semiconductor laser that converts an input electrical signal into optical output, and 2 is a semiconductor laser 1.
3 is a pulse current drive circuit that drives the semiconductor laser 1 with a pulse current as the electric signal, and 4 is an optical output of the semiconductor laser 1. 5 is an automatic output power control circuit (as an output stabilizing circuit) connected to the bias current supply circuit 2 to keep the optical output constant.
(hereinafter referred to as an APC circuit).

Next, the operation will be explained.

The semiconductor laser 1 has a bias current supply circuit 2. It is driven and controlled by a pulse current drive circuit 3 and an APC circuit 5. That is, first, the pulse drive circuit 3 operates upon receiving a pulse signal input from the outside, and drives the semiconductor laser 1. In this case, the bias current supply circuit 2 functions to compensate the current-optical output characteristics of the semiconductor laser 1.

That is, since this semiconductor laser 1 generally emits light by passing a current exceeding a threshold current, the bias current drive circuit 2 supplies such a threshold current to the semiconductor laser 1. On the other hand, the driving state of the semiconductor laser 1 is detected by the photodiode 4, and the APC circuit 5 monitors the backlight of the semiconductor laser 1 based on the detection output, and the bias current supply circuit 2 is controlled according to the monitor output. By controlling this, the semiconductor laser 1 is stably driven.

[Problem to be solved by the invention]

Since conventional semiconductor laser drive devices are configured as described above, when manufacturing a large number of such semiconductor laser drive circuits, it is necessary to adjust the differences in characteristics of individual semiconductor lasers. Bias current supply circuit 2. It is necessary to adjust the pulse current drive circuit 3 and the APC circuit 5 according to the semiconductor laser 1 that uses them.
There were problems such as the operation of the C circuit 5 changed and a load being applied to the semiconductor laser 1. Note that a technology similar to such a conventional semiconductor laser driving device is disclosed in Japanese Patent Application Laid-Open No. 1-304792.
It is stated in the No.

This invention was made to solve the above-mentioned problems, and it not only makes it possible to shorten the adjustment time of light output, but also
It is an object of the present invention to provide a semiconductor laser driving device that can always obtain stable optical output by compensating the duty of the optical output waveform.

[Means to solve the problem]

A semiconductor laser driving device according to the present invention includes: a pulse instantaneous circuit that drives a semiconductor laser with a pulsed current; a light monitor element that monitors the light output of the semiconductor laser; and an automatic output power control circuit that controls the pulse drive circuit so as to keep the output constant, and a duty compensation circuit compensates for changes in duty of the optical output waveform based on the output of the output element of the optical monitor element. It was designed to do so.

[Effect]

The duty compensation circuit according to the present invention functions to compensate for changes in the duty of the optical output waveform of the semiconductor laser obtained from the optical monitor element, thereby simplifying the stabilization control of the optical output without increasing the number of adjustment items. In addition to making it possible to implement it.

It also makes it possible to prevent deterioration of transmission characteristics such as extinction ratio deterioration.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a semiconductor laser, 3 is a pulse drive circuit for pulse-driving the semiconductor laser 1, 4 is a photodiode as a light monitor element for monitoring the output of the semiconductor laser, and 5 is a device for obtaining stable light output. APC circuit,
6 is a duty compensation circuit that compensates for changes in duty of the optical output waveform.

Next, the operation will be explained.

First, the pulse drive circuit 3 activates the semiconductor laser 1 based on a pulse signal input from the outside. When the semiconductor laser 1 is driven in this manner, the drive output state is monitored by the photodiode 4, and the output waveform of the photodiode 4, which is the monitored output, is input to the duty compensation circuit 6. For this reason, the duty compensation circuit 6 controls the instantaneous pulse circuit 3 to drive the semiconductor laser 1 so as to adjust the duty of the optical output waveform. By using such a duty compensation circuit 6, there is no need to consider the temperature characteristics of each individual semiconductor laser 1.
There is no need for adjustment by the bias current drive circuit 2 as in the conventional case. Further, at this time, the APC circuit 5 receives the output of the photodiode 4 that monitors the semiconductor laser 1, and controls the pulse drive circuit 3 so that the optical output is constant.

In the above embodiment, the duty compensation circuit 6 operates in an analog manner, but as shown in FIG. , it is also possible to improve the control accuracy of the above-mentioned duty.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a pulse drive circuit that drives a semiconductor laser with a pulse current, a light monitor element that monitors the optical output of the semiconductor laser, and a pulse drive circuit that monitors the light output based on the output of the light monitor element. and an automatic output power control circuit that controls the pulse drive circuit so as to keep constant, and a duty compensation circuit compensates for duty changes in the optical output waveform based on the output of the output element of the optical monitor element. With this configuration, the semiconductor laser drive circuit can be driven only by the pulse drive circuit, reducing the number of adjustment items, and the duty of the optical output waveform can be adjusted to prevent deterioration of transmission characteristics such as extinction ratio deterioration. This has the effect of providing something that can prevent this.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a semiconductor laser driving device according to one embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment of the semiconductor laser driving device according to the present invention, and FIG. 3 is a block diagram showing a conventional semiconductor laser driving device according to an embodiment of the present invention. FIG. 2 is a block diagram showing a dynamic device. 1 is a semiconductor laser, 3 is a pulse drive circuit, 4 is a light monitor element (photodiode), 5 is an automatic output power control circuit (APC circuit), and 6 is a duty compensation circuit. In Figure 1, the same reference numerals indicate the same or equivalent parts. Figure 1 Figure 2 Each member of the group

Claims (1)

[Claims] a pulse drive circuit that drives the semiconductor laser with a pulsed current; a light monitor element that monitors the optical output of the semiconductor laser; A semiconductor laser driving device comprising: an automatic output power control circuit that controls the circuit; and a duty compensation circuit that compensates for changes in duty of the optical output waveform based on the output of the optical monitor element.