JPH07107042A - Optical transmission circuit - Google Patents

Abstract

PURPOSE:To reduce control signals to a transmission circuit and to hold light output fixed in the optical transmission of burst signals. CONSTITUTION:The light output 9 of a light emitting element 1 driven by a light emitting element driving circuit 3 to which input signals 8 are inputted is received by a monitor detector 2 and the output 10 is outputted as the output 11 peak-held by a peak value holding circuit 4. Also, a pseudo monitoring signal shaping circuit 5 generates pseudo signals 12 equivalent to the output 10 from the input signals 8. The output 12 is inputted to a pseudo monitor peak value holding circuit 6 and turned to the output 13. The output 11 and 13 are inputted to a differential amplifier 7, the output is fed back to the driving circuit 3 and thus, the light emitting element driving circuit 3 holds the light output 9 of the light emitting element 1 fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission circuit, and more particularly to a data input of the optical transmission circuit, which is divided into a transmission period for transmitting a signal and a non-transmission period for not transmitting the signal, and The present invention relates to an optical transmission circuit that enables constant control of optical output in an optical transmission circuit that is a low-level burst signal.

[0002]

2. Description of the Related Art As a conventional technique relating to an optical transmission circuit, for example, a technique which is announced as a paper number B-417 at the Autumn National Conference of the Institute of Electronics, Information and Communication Engineers in 1988 is known.

FIG. 3 is a block diagram showing the circuit configuration of a conventional optical transmission circuit, and FIG. 4 is a signal waveform diagram for explaining the operation of the conventional technique. In FIG. 3, 31 is a signal addition circuit, 32 is a laser diode (LD), 33 is a monitor peak value hold circuit, 34 is a charging circuit, 35 is a sample & hold (S & H) circuit, and 36 is a sample & hold (S & H) control. Reference numeral 37 is a circuit, 37 is a voltage comparison circuit, 38 is an amplifier, 39 is a low-pass filter, and 40 is a reference voltage source.

As shown in FIG. 3, the optical transmitter circuit according to the prior art has a signal adder circuit 31, a laser diode (LD) 32, a monitor peak value hold circuit 33, and a charging circuit 34 to which a burst input signal 41 is input. A sample & hold circuit 35, a sample & hold control circuit 36 having a burst gate signal 42 and a start / stop signal 43 as an input source, a voltage comparison circuit 37, an amplifier 38, a low pass filter 39, and a reference voltage source 40. It is configured.

Then, the illustrated optical transmission circuit operates as follows in the activated state. That is, the signal addition means 3
In No. 1, the burst-shaped input signal 41 and the feedback signal from the low-pass filter 39 that makes the optical output constant are added to drive and control the LD 32. The optical output from the LD 32 is monitored by a monitor peak value hold circuit 33, and its output is controlled via a charging circuit 34 by a sample & hold control circuit 36 using a burst gate signal 42 and a start / stop signal 43 as input sources. The sample and hold circuit 35 is input.

As a result, the sample & hold circuit 35 outputs the input signal 41 as a continuous monitor signal. This monitor signal is compared with the reference voltage from the reference voltage source 40. This comparison output signal is given to the signal addition circuit 31 via the amplifier 38 and the low-pass filter 39, and is used to keep the optical output of the laser diode 32 constant.

To make the monitor signal continuous, the charging circuit 34 is used to hold the monitor signal at a high level without being affected by the pulse modulation state during the burst transmission period, and the sample-and-hold circuit 35 is held during the non-transmission period. This can be done by interpolating the high level held using.

The conventional optical transmission circuit shown in FIG.
As described above, since the monitor signal is made continuous by combining the charging circuit 34 and the sample & hold circuit 35, even if the pulse modulation speed is high and the non-transmission period is long, the optical output can be accurately output. It can be kept constant.

Further, in the circuit of this prior art, in the stop state, the voltage level of the reference voltage source 40 is switched to the low level by the start / stop signal 43, and the sample & hold circuit 35 is kept in the sample state, so that the laser The light output from the diode 32 can be maintained at a low level.

The optical transmission circuit according to the prior art has the advantage that it can perform automatic optical output control for stabilizing the optical output with high accuracy at the time of transmitting a burst signal by providing the above-mentioned configuration. ing.

[0011]

However, the above-described conventional technique requires three signals, that is, a burst-like transmission input signal, a burst gate signal, and a start / stop signal as a control signal of the transmission circuit, which makes the control complicated. There is a problem that

In the prior art described above, the rise time of the optical output when the circuit is changed from the stopped state to the activated state is the burst signal by charging the bias signal by the time constant of the low-pass filter of the feedback section. It takes about several tens of cycles, which causes a problem that the optical output is output as a distorted waveform for a while even if the activation signal is input.

An object of the present invention is to solve the above-mentioned problems of the prior art, to reduce the number of control signals to the transmission circuit to facilitate control, and to control the optical output between a transmission period and a non-transmission period. Completely, and when the optical output rises,
It is an object of the present invention to provide an optical transmission circuit capable of holding an optical output instantaneously constant.

[0014]

According to the present invention, the object is to fix the output of a monitor detector for monitoring the light output of a light emitting element at a high level by a peak value hold circuit while the control circuit is in an activated state. Pseudo monitor peak that outputs the same and generates a pseudo signal similar to the output of the monitor detector from the input signal to the pseudo monitor signal shaping circuit, and performs the same operation as the peak value hold circuit. By inputting to the value hold circuit to generate a pseudo monitor signal, and feeding back the output of the differential amplifier having the monitor signal and the pseudo monitor signal as input sources to the current source of the light emitting element drive circuit. To be achieved.

The optical transmission circuit of the present invention, having the above-mentioned configuration, can keep the light output from the light emitting element constant.

[0016]

A burst-like transmission signal that is turned on only during the transmission period is input to the light emitting element drive circuit, and the light emitting element drive circuit controls so that an optical output is obtained from the light emitting element. This optical output is detected by the monitor detector, and its signal is input to the peak value hold circuit. The peak value hold circuit outputs the output signal as a high fixed output while the signal is input. Further, the pseudo monitor signal shaping circuit and the pseudo monitor peak value hold circuit generate a pseudo signal for the output signal from the monitor detector output and the peak value hold circuit from the input signal as a pseudo monitor signal. Then, the monitor signal and the pseudo monitor signal are input to the differential amplifier, and the output thereof is fed back to the drive current of the light emitting element drive circuit.

According to the present invention, therefore, the optical output corresponding to the burst signal which is turned on only during the transmission period can be kept constant.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical transmission circuit according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention, and FIG. 2 is a signal waveform diagram for explaining the operation of the embodiment of the present invention. In FIG. 1, 1 is a light emitting element, 2 is a light emitting element optical output monitor detector, 3 is a light emitting element driving circuit,
Reference numeral 4 is a peak value hold circuit, 5 is a pseudo monitor signal shaping circuit, 6 is a pseudo monitor peak value hold circuit, and 7 is a differential amplifier.

As shown in FIG. 1, an optical transmitter circuit according to an embodiment of the present invention receives a light emitting element 1 and a burst-shaped transmission input signal 8 and drives the light emitting element 1 by this signal. The circuit 3, the light emitting element optical output monitor detector 2 that receives the optical output 9 from the light emitting element 1, the peak value hold circuit 4 that holds the output signal 10 from the monitor detector 2, and the transmission input signal 8 Pseudo monitor signal shaping circuit 5 to be inputted, pseudo monitor peak value hold circuit 6 to which the output signal of the circuit 5 is inputted, output signal 11 of the peak value hold circuit 4 and output signal of the pseudo monitor peak value hold circuit 6. 13 is input, and a differential amplifier 7 that generates a control signal 14 for the light emitting element drive circuit 3 is configured.

In the optical transmission circuit according to the embodiment of the present invention shown in FIG. 1, the light output 9 from the light emitting element 1 driven by the light emitting element drive circuit 3 to which the burst-shaped transmission input signal 8 is input is the light emission. The element light output monitor detector 2 receives the light. The output signal 10 of the monitor detector 2 is peak-held by the peak-value holding circuit 4, and the output signal 1
It is output as 1. Also, the pseudo monitor signal shaping circuit 5
The pseudo monitor peak value hold circuit 6 receives the burst-like transmission input signal 8 as an input and the pseudo monitor signal 1
3 is generated and output.

The output signal 11 from the peak value hold circuit 4 and the pseudo monitor peak value hold circuit 6 are also provided.
The output signal 13 from each of them is input to the differential amplifier 7, and the output signal is fed back to the current source (not shown) in the light emitting element drive circuit 3 as a feedback signal to the light emitting element drive circuit 3 via the feedback loop. It

Next, the operation of each circuit will be described with reference to the waveforms and timing charts of the input and output signals in each of the constituent circuits shown in FIG.

In FIG. 2, when the transmission input signal 8 is input to the light emitting element drive circuit 3, a light output 9 is output from the light emitting element 1, and this light output 9 is received by the light emitting element light output monitor detector 2. Output signal 10
Is obtained. The peak value holding circuit 4 has a time constant sufficiently longer than the non-transmission period of the transmission input signal 8. Therefore, when the output signal 10 is input, the peak value is held until the next transmission period. The generated output signal 11 is generated and output.

Further, the pseudo monitor signal shaping circuit 5 receives the transmission input signal 8 and, based on this input signal, the pseudo output signal 1 with respect to the output signal 10 of the monitor detector 2.
2, the pseudo monitor peak value hold circuit 6 is supplied with the pseudo output signal 12, and based on the signal 12, a signal having substantially the same shape as the peak value hold circuit output signal 11 is generated as a pseudo monitor peak. The value hold circuit output signal 13 is generated and output.

These output signals 11 and 13 are input to the differential amplifier 7, respectively. As a result, the output signal 14 of the differential amplifier 7 becomes a signal having a stable and constant level output without being influenced by the burst-shaped transmission input signal 8. The amplifier output signal 14 is fed back to the current source of the light emitting element drive circuit 3. As a result, the burst-type transmission input signal 8 is input to the light-emitting element drive circuit 3, and at the same time, a sufficient drive voltage for holding the optical output 9 of the light-emitting element 1 stably is input. Will be supplied.

As described above, according to one embodiment of the present invention, the control signal input to the optical signal transmission circuit is the transmission input signal only, and the optical output is completely divided into the transmission period and the non-transmission period. Moreover, it is possible to instantaneously keep the optical output constant when the optical signal rises.

[0028]

As described above, according to the present invention, in the optical transmission of a burst signal, only a burst-shaped transmission input signal is input as an input signal to the transmission circuit, and the optical output is transmitted during the transmission period and non-transmission. It is possible to provide an optical transmission circuit that can be completely divided into a period and a constant optical output during the transmission period.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a signal waveform for explaining the operation of one embodiment of the present invention,
FIG. 6 is a diagram showing the timing of input / output signals.

FIG. 3 is a block diagram showing a circuit configuration of a conventional optical transmission circuit.

FIG. 4 is a signal waveform diagram for explaining the operation of the conventional technique.

[Explanation of symbols]

 1 Light emitting element 2 Light emitting element optical output monitor detector 3 Light emitting element drive circuit 4 Peak value hold circuit 5 Pseudo monitor signal shaping circuit 6 Pseudo monitor peak value hold circuit 7 Differential amplifier

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H04B 10/28 10/26 H04L 25/02 S 9199-5K (72) Inventor Hitoshi Hashimoto Chiyoda, Tokyo 1-6-1, Saiwaicho in the city Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A light provided with a light emitting element drive circuit which is divided into a transmission period in which a signal is transmitted and a non-transmission period in which a signal is not transmitted, and which drives a light emitting element using a burst signal which is at a low level in the non-transmission period as an input source. In the transmission circuit, the optical output from the light emitting element is monitored to generate a monitor signal that becomes a high level fixed output while the optical transmission circuit is in the activated state, and a pseudo signal similar to the monitor signal is generated. , An optical transmission which is generated from the burst signal as a pseudo monitor signal, and which outputs the output of a differential amplifier having the monitor signal and the pseudo monitor signal as input sources to the current source of the light emitting element drive circuit. circuit. 2. The monitor signal is generated by a light emitting element monitor detector and a monitor signal peak value hold circuit having an input source of a signal whose light emitting period is monitored by the monitor detector, and the pseudo monitor signal is 2. The optical transmission circuit according to claim 1, wherein the optical transmission circuit is generated by a pseudo monitor signal shaping circuit having a burst signal as an input source and a pseudo monitor signal peak value hold circuit having an output signal of the shaping circuit as an input source.