JPH0522232A - Optical reception circuit - Google Patents

Abstract

PURPOSE:To make the output amplitude constant and to adjust a changeover circuit unifiedly by detecting an amplitude of a clamped electric signal so as to control a limiter stage number in matching with the optical signal level subject to amplitude modulation. CONSTITUTION:An electric signal inputted to a band limit filter 3 from a photoelectric conversion circuit 1 is converted into a waveform easily identified and the result is outputted to a multi-stage limiter circuit 7. The stage number in matching with an optical signal subject to amplitude modulation is selected by the electric signal and clamped to the amplitude close to the logic level and the result is outputted to an identification circuit 6 and a changeover circuit 8. The electric signal is used to control the limiter stage number to detect an output amplitude of the multi-stage limiter circuit 7 and to make it constant. Furthermore, the electric signal inputted to the identification circuit 6 from the multi-stage limiter circuit 7 is identified and recovered at the logic level by a comparator. Thus, the gain control adjustment for each circuit is not required by controlling the output amplitude through the changeover of the limiter stage number by the control of the changeover circuit in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiving circuit for converting an optical signal whose amplitude has been converted into an electric signal.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a conventional optical receiving circuit. In the figure, reference numeral 1 is a circuit for converting an amplitude-modulated optical signal into an electric signal and amplifying the electric signal, and a photodiode and a preamplifier. An opto-electric conversion circuit composed of a combination of circuits, 2 is a linear amplification circuit that receives a signal from the opto-electric conversion circuit 1 and linearly amplifies, and 3 is a signal that is received from the linear amplification circuit 2 and band-limited to facilitate signal identification. It is a band limiting filter that converts to a waveform. 4 is a limiter circuit for receiving a signal from the band limiting filter 3 and clamping it to an amplitude close to a logical level, 5 is a control circuit for receiving a signal from the limiter circuit 4 and feeding it back to the linear amplification circuit 2 to control the gain, 6 is a limiter circuit 4 It is an identification circuit that receives a signal and identifies and reproduces it at a logic level.

Next, the operation will be described. The optical signal input to the photoelectric conversion circuit 1 is converted into an electric signal, amplified, and output to the linear amplification circuit 2. The electrical signal input from the photoelectric conversion circuit 1 to the linear amplification circuit 2 is amplified to a required amplitude and output to the band limiting filter 3. The electric signal input from the linear amplification circuit 2 to the band amplification limiting filter 3 is band-limited, converted into a waveform in which the signal can be easily identified, and output to the limiter circuit 4.

The electric signal input from the band limiting filter 3 to the limiter circuit 4 is amplified, clamped to an amplitude close to the logic level, and output to the control circuit 5 and the discrimination circuit 6.
The electric signal input from the limiter circuit 4 to the control circuit 5 linearly controls the gain of the linear amplification circuit 2 so that the amplitude becomes constant. The electric signal input from the limiter circuit 4 to the discrimination circuit 6 is discriminated and reproduced at a logical level by the comparator. Also, when it has a 3R function, a clock is extracted from the signal and reproduced.

[0005]

Since the conventional optical receiving circuit is constructed as described above, it is linear in order to make the amplitude of the output signal of the linear amplifier circuit 2 constant regardless of the input level of the optical signal. Therefore, it was necessary to adjust the control circuit 5 for that purpose. Further, there is a problem in that the adjustment of the control circuit 5 is difficult because the individual elements have different characteristics, so that it is necessary to adjust each circuit.

The present invention has been made in order to solve the above-mentioned problems, and does not require adjustment for each circuit due to the characteristic difference of individual elements, and enables uniform adjustment, thereby improving efficiency. At the same time, it aims to obtain a highly reliable optical receiving circuit.

[0007]

In the optical receiver circuit according to the invention described in claim 1, the limiter circuit is a multi-stage limiter circuit capable of selecting the number of limiter stages corresponding to the amplitude-modulated optical signal level. By using the switching circuit to control the selection of the number of limiter stages of the circuit, the linear amplifier circuit and the control circuit are unnecessary.

The optical receiving circuit according to the invention described in claim 2 is the optical receiving circuit according to the invention described in claim 1,
The switching circuit and the multistage limiter circuit are controlled by digital signals by using an analog / digital conversion circuit that converts an electric signal from the multistage limiter circuit into a digital signal.

The optical receiver circuit according to the invention described in claim 3 is the same as the optical receiver circuit according to the invention described in claim 1,
The opto-electric conversion circuit is composed of an avalanche photodiode and a preamplifier circuit, and a high voltage generation circuit that inputs a control signal from a switching circuit to generate a high voltage is used to control the avalanche photodiode. Is.

[0010]

In the multistage limiter circuit according to the present invention, the amplitude of the electric signal clamped by the switching circuit is detected, and the number of limiter stages is controlled in accordance with the amplitude-modulated optical signal level. The output amplitude can be kept constant, and the switching circuit can be uniformly adjusted.

According to the second aspect of the invention, the analog / digital conversion circuit converts the electric signal, which is an analog signal, into a digital signal from the multistage limiter circuit, and converts the control of the switching circuit and the multistage limiter circuit into a digital signal.

The apalanche photodiode of the photoelectric conversion circuit according to the third aspect of the present invention controls the amplification factor by the high voltage of the high voltage generation circuit to which the control signal is input from the switching circuit, and a wider receiving area. To get

[0013]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In the figure, the same components as those shown in FIG. 4, which is a conventional technique, are designated by the same reference numerals, and the duplicate description thereof will be omitted. FIG. 1 is a block diagram showing an optical receiving circuit according to an embodiment of the invention described in claim 1. In the figure, 7 is the number of limiter stages corresponding to the optical signal level which is received from the filter circuit 3 and is amplitude-modulated. , And a multi-stage limiter circuit for clamping to an amplitude close to the logic level, 8 receives a signal from the multi-stage limiter circuit 7 to detect the output amplitude of the multi-stage limiter circuit, and to keep the output amplitude of the multi-stage limiter circuit 7 constant, It is a switching circuit for controlling.

The next operation will be described. The amplitude-modulated optical signal input to the photoelectric conversion circuit 1 is converted into an electric signal, amplified, and output to the band limiting filter 3. The electric signal input from the photoelectric conversion circuit 1 to the band limiting filter 3 is band-limited, converted into a waveform in which the signal can be easily identified, and output to the multistage limiter circuit 7. For the electric signal input from the band limiting filter 3 to the multi-stage limiter circuit 7, the number of stages corresponding to the amplitude-modulated optical signal level is selected, clamped to an amplitude close to the logical level, and output to the discrimination circuit 6 and the switching circuit 8. .

The electric signal input from the multi-stage limiter circuit 7 to the switching circuit 8 detects the output amplitude of the multi-stage limiter circuit 7 and controls the number of limiter stages in order to make the output amplitude of the multi-stage limiter circuit 7 constant. In addition, multi-stage limiter circuit 7
The electric signal input to the discriminating circuit 6 is discriminated and reproduced at a logical level by the comparator. As described above, the output amplitude of the multi-stage limiter circuit 7 is switched by switching the number of limiter stages under the control of the switching circuit 8, so that gain control adjustment for each circuit is not necessary.

Example 2. In the second embodiment, the control of the switching circuit and the like is performed by analog, but it is also possible to control digitally by using an analog / digital conversion circuit (hereinafter referred to as A / D conversion circuit).

FIG. 2 is a block diagram showing an optical receiving circuit according to the invention described in claim 2, and FIG.
Is a multi-stage limiter circuit that receives an electric signal from the filter circuit 3 and selects the number of stages commensurate with the optical signal level, and clamps at an amplitude close to the logical level, and 10 receives an electric signal that is an analog signal from the multi-stage limiter circuit 9, A / D conversion circuit for converting signal to digital signal, 11
Is a switching circuit that receives a digital signal from the A / D conversion circuit 10, detects the output amplitude of the multi-stage limiter circuit 9 with the digital signal, and controls the number of limiter stages of the multi-stage limiter circuit 9 with the digital signal.

As described above, the A / D conversion circuit 10 is used to control the multi-stage limiter circuit 9 and the switching circuit 11 by digital signals, whereby functions such as waveform reproduction and duty correction of the output signal of the multi-stage limiter circuit 9 are performed. There is an effect that can be realized.

Example 3. Further, in the above-described first and second embodiments, the photoelectric conversion circuit 1 is configured by the combination of the photodiode and the preamplifier circuit. However, this is configured by the combination of the apalanche photodiode and the preamplifier circuit. It is also possible to do so.

FIG. 3 is a block diagram showing an optical receiving circuit according to the invention described in claim 3, in which 12 is an apalanche photo amplifier for converting an amplitude-modulated optical signal into an electric signal and amplifying the electric signal. The photoelectric conversion circuit is configured by a combination of a diode and a preamplifier circuit and outputs the band limiting filter 3. 13 receives the control signal from the switching circuit 8 and receives the control signal from the photoelectric conversion circuit 12.
It is a high voltage generation circuit that generates a high voltage to be supplied to the photodiode.

Next, the operation will be described. The high voltage output from the high voltage generation circuit 13 is controlled by the control signal from the switching circuit 8. On the other hand, the amplification factor of the apalanche photodiode of the photoelectric conversion circuit 12 is controlled by the high voltage input from the high voltage generation circuit 13. In this way, the high voltage generating circuit 1 is controlled by the control signal of the switching circuit 8.
This high voltage generation circuit 1 controls the high voltage generated by
By controlling the amplification factor of the photoelectric conversion circuit 12 by the high voltage generated by the signal No. 3, the effect that a wider reception area can be obtained for the vibration-modulated optical signal level input to the photoelectric conversion circuit 12 is obtained. is there.

[0022]

As described above, according to the invention of claim 1, the limiter circuit is a multi-stage limiter circuit capable of selecting the number of limiter stages corresponding to the amplitude-modulated optical signal level, and the limiter of this multi-stage limiter circuit is selected. Since a switching circuit is used to control the selection of the number of stages, a linear amplification circuit and a control circuit are not required, and adjustments for each circuit due to the characteristic differences of individual elements are not required, allowing uniform adjustment. Thus, there is an effect that an optical receiving circuit having high efficiency and high reliability can be obtained.

According to the invention of claim 2, in addition to the invention of claim 1, an analog / digital conversion circuit for converting an electric signal, which is an analog signal from the multistage limiter circuit, into a digital signal is used. Since the switching circuit and the multi-stage limiter circuit can be controlled by the digital signal, it is possible to realize functions such as waveform reproduction and duty correction of the output signal of the multi-stage limiter circuit.

Further, according to the invention described in claim 3, in addition to the invention described in claim 1, the photoelectric conversion circuit has a configuration of an aparanche photodiode and a preamplifier circuit, and the aparanche photodiode is used. Since a control signal is input from the switching circuit to control the high voltage generation circuit that generates a high voltage, the amplitude-modulated optical signal level input to the photoelectric conversion circuit is The effect is that a wider receiving area can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an optical receiving circuit according to an embodiment of the invention described in claim 1.

FIG. 2 is a block diagram showing an optical receiving circuit according to an embodiment of the invention described in claim 2;

FIG. 3 is a block diagram showing an optical receiving circuit according to an embodiment of the invention described in claim 3;

FIG. 4 is a block diagram showing a conventional optical receiving circuit.

[Explanation of symbols]

1,12 Photoelectric conversion circuit 3 Band limiting filter 6 identification circuit 7,9 Multi-stage limiter circuit 8, 11 switching circuit 10 Analog / digital conversion circuit 13 High voltage generation circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04L 27/06 Z 9297-5K

Claims (3)

[Claims] 1. An opto-electrical conversion circuit for converting an amplitude-modulated optical signal into an electric signal and for amplifying the electric signal, and an electric signal amplified by the opto-electrical conversion circuit is converted into a waveform that is easy to identify. In order to input a band-limited filter for band-limiting and an electric signal band-limited by the band-limiting filter, select the number of limiter stages corresponding to the amplitude-modulated optical signal level, and clamp to an amplitude close to the logical level. A multi-stage limiter circuit, a switching circuit for detecting the amplitude of the electric signal clamped by the multi-stage limiter circuit, and controlling the number of limiter stages in order to make the output amplitude of the multi-stage limiter circuit constant, and the switching circuit clamped by the multi-stage limiter circuit. An optical receiving circuit provided with an identification circuit which inputs an electric signal and performs identification reproduction by a comparator to a logical level. 2. A multi-stage limiter for inputting an electric signal band-limited by the band-limiting filter, selecting the number of limiter stages corresponding to the amplitude-modulated optical signal level by a digital signal, and clamping to an amplitude close to a logical level. Circuit and an analog / digital conversion circuit for inputting the electric signal clamped by the multi-stage limiter circuit and converting it into a digital signal, and a digital signal for inputting from the analog / digital conversion circuit, and changing the output amplitude of the multi-stage limiter circuit. 2. The optical receiving circuit according to claim 1, further comprising a switching circuit that detects the digital signal and controls the number of limiter stages with a digital signal in order to keep the output amplitude of the multistage limiter circuit constant. 3. An apalanche photodiode and a preamplifier circuit, in which an amplitude-modulated optical signal is converted into an electric signal, the electric signal is amplified, and the amplification factor is controlled by being supplied with a high voltage. 2. A photoelectric conversion circuit configured by the above, and a high voltage generation circuit that generates a high voltage that is supplied with a control signal from the switching circuit and that is supplied to an apalanche photodiode of the photoelectric conversion circuit. Optical receiver circuit.