JPS63290419A - Ld driving circuit - Google Patents

Abstract

PURPOSE:To automatically suppress the peaking of an optical output waveform due to relaxation oscillation by providing a peak value detecting circuit detecting a peak value from the output of a photodetector and a DC amplifying circuit comparing the peak value of the peak value detecting circuit with a reference value and applying its output to a control terminal of a waveform correcting circuit. CONSTITUTION:In giving a digital signal to a signal input terminal 9, the signal driving circuit 1 lights a semiconductor laser 2. The light radiated from the semiconductor laser 2 is received by a photodetector 3, the mean value of a monitor light is detected by a mean value detecting circuit 4, it is inputted to a DC bias circuit 5 to control the output power of the semiconductor laser 2. Simultaneously, the peak value of the received light is detected by a peak value detecting circuit 7, it is compared with the reference voltage by a DC amplifying circuit 8 and amplified to use the output information thereby controlling a waveform correction circuit 10 and automatically suppressing the peaking of the optical output waveform.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical transmission circuit for a digital optical communication system,
In particular, an LD (laser diode) is used as a light source.

The present invention relates to an LD drive circuit using an LD (hereinafter referred to as LD).

[Conventional technology]

FIG. 2 shows a conventional LD drive circuit.

Signal drive circuit 1. Semiconductor laser 2. Photoreceiver 3° Average value detection circuit 4. DC/Gear circuit 5. It is composed of a waveform correction circuit 6, and causes the semiconductor laser 2 to emit light by the signal drive circuit 1 based on a digital signal input to a signal input terminal 9. The monitor light emitted from the semiconductor laser 2 is received by the light receiver 3, the average value of the received monitor light is detected by the average value detection circuit 4, and this is input to the DC/Gear circuit 5 to detect the average value of the received monitor light. control the output power of the

At this time, if there is a peak in the optical output waveform.

While observing the optical output waveform, peaking was suppressed using a waveform correction circuit 6 (a circuit composed of a resistor, a capacitor, etc.).

[Apex while the invention is trying to solve]

As mentioned above, conventional LD drive circuits suffer from peaking in the optical output waveform caused by relaxation oscillation.

This is suppressed by an LD optical output waveform correction circuit composed of a resistor and a capacitor. However, since each LD has a different relaxation oscillation frequency, it is difficult to correct the optical output waveform because the constants of the waveform correction circuit are selected to suppress peaking while observing the optical output waveform of each LD.

[Means for solving problems]

The present invention provides a signal drive circuit that receives a digital signal as an input, a DC bias circuit that outputs a DC bias current, an output current of the signal drive circuit, and a DC output current of the DC bias circuit as inputs. a semiconductor laser that oscillates a laser beam, a light receiver that detects the output light of the semiconductor laser, an average value detection circuit that detects an average value from the output of the light receiver, and an output of the average value detection circuit that is connected to the DC bias circuit. In the semiconductor laser driving circuit that applies an electric current to It is characterized in that it is provided with a DC amplification circuit that applies voltage to the control terminal.

〔Example〕

FIG. 1 shows an embodiment of the present invention. Based on the digital signal input to the signal input terminal 9, the signal drive circuit 1
The semiconductor laser 2 is caused to emit light. The monitor light emitted from the semiconductor laser 2 is received by the light receiver 3, the average value of the received monitor light is detected by the average value detection circuit 4, and this is input to the DC bias circuit 5 to calculate the output power of the semiconductor laser 2. control. At the same time, the peak value of the received monitor light is detected by the peak value detection circuit 7, which is compared with a reference voltage by the DC amplifier circuit 8, and the waveform correction circuit 10 having a control terminal is controlled by the output information. .

Automatically suppresses peaking in the optical output waveform.

As an example of the waveform correction circuit 10 having a control terminal,
There is a series circuit of resistors and Paris caps. When the relaxation oscillation is large and the peak of the optical output waveform is large, the output of the peak value detection circuit 7 becomes large.

Feedback is applied to reduce the control voltage of the Paris cap, increase the capacitance of the Paris cap, and reduce the peak of the optical output waveform. Note that the reference voltage is set slightly higher than the voltage corresponding to the 1" level of the optical output waveform. Also, a circuit for DC amplifying the amount of light received by the optical receiver is connected to the optical receiver, the average value detection circuit, and the peak value detection circuit. Needless to say, peaking can be automatically suppressed even if it is connected between detection circuits.

〔Effect of the invention〕

As explained above, the present invention connects a DC amplifier circuit to a waveform correction circuit having a peak value detection circuit and a control terminal instead of the conventional waveform correction circuit, thereby achieving peaking of the optical output waveform due to relaxation oscillation. can be suppressed automatically. In addition.

Ringing caused by the constants of the LD drive circuit can also be suppressed.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the LD drive circuit of the present invention, and
The figure shows a conventional LD drive circuit. 1... Signal drive circuit, 2... Semiconductor radar, 3...
- Light receiver, 4... Average value detection circuit, 5... DC bias circuit, 6... Waveform correction circuit, 7... Peak value detection circuit. 8... DC amplifier circuit, 10... Waveform correction circuit having a control terminal.

Claims (1)

[Claims] 1. A signal drive circuit that inputs a digital signal, a DC bias circuit that outputs a DC bias current, and oscillates an optical pulse using the output current of the signal drive circuit and the DC output current of the DC bias circuit as inputs. It has a semiconductor laser, a light receiver that detects the output light of the semiconductor laser, and an average value detection circuit that detects an average value from the output of the light receiver, and the output of the average value detection circuit is sent to the DC bias circuit. In the semiconductor laser drive circuit that applies the voltage, a peak value detection circuit detects the peak value from the output of the light receiver, and the peak value of the peak value detection circuit is compared with a reference value, and the output is sent to the control terminal of the waveform correction circuit. 1. An LD drive circuit comprising: a DC amplifier circuit that applies a direct current to the LD drive circuit;