JPH0779356B2 - Optical receiver - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver used for high-speed digital optical transmission or the like in which a signal duty ratio on a transmission line is constant.

2. Description of the Related Art FIG. 5 is a circuit block diagram showing a configuration of a conventional optical receiver. In FIG. 5, 1 is a light receiving element, 2 is a current / voltage converter, 15 is an AGC amplifier, 16 is a final stage amplifier, 1
7 is a voltage comparator (comparator), 18 is a peak detector, 1
Reference numeral 9 is a reference power source, and 4 is a binary signal which is an optical receiver output signal.

The anode terminal of the light receiving element 1 is connected to the current / voltage converter 2, and the output terminal of the current / voltage converter 2 is an AGC amplifier 15.
The output terminal of the AGC amplifier 15 is connected to the final stage amplifier 16, and the output terminal of the final stage amplifier 16 is connected to one input terminal of the comparator 17 and the peak detector 18, respectively. The output signal of the peak detector 18 is input as the control input of the AGC amplifier 15. In addition, the reference power source 19
Is connected, and the binary signal 4 which is the optical receiver output signal is output from the comparator 17.

Next, the operation of the above conventional example will be described. In FIG. 5, the light received by the light receiving element 1 is converted into a current signal and then converted into a voltage signal by the current / voltage converter 2. This voltage signal is amplified by the AGC amplifier 15 and the final stage amplifier 16, and then compared with the preset reference voltage of the reference power source 19 by the voltage comparator 17 to obtain the binary signal 4
Is output. Here, since the input signal of the voltage comparator 17 is fed back to the control input of the AGC amplifier 15 via the peak detector 18, the gain of the AGC amplifier 15 is changed and the AGC operation is realized.

That is, even if the reception level of the light receiving element 1 changes, the AGC
By the action of the feedback loop of the amplifier 15, the final stage amplifier 16, and the peak detector 18, the operation is performed so that the amplitude of the signal input to the voltage comparator 17 becomes constant.

As described above, even the conventional optical receiver described above can perform the binarization operation even if the reception level changes.

However, in the above conventional optical receiving device, the effect of suppressing the amplitude fluctuation of the input signal of the voltage comparator 17 based on the fluctuation of the reception level is realized by the feedback function of the AGC loop, so that the loop delay time. However, there is a problem in that the response to fluctuations in the reception level cannot be speeded up. Further, since the AGC loop includes a non-linear element such as the peak detector 18, it is difficult to design the loop characteristic, that is, to stabilize the transfer characteristic.
Further, there is a problem that it is difficult and difficult to adjust the slice level when binarizing the signal.

The present invention solves such conventional problems, and an object of the present invention is to provide an excellent optical receiving device which is easy to design, can realize a high-speed response, and can be adjusted. .

Means for Solving the Problems In order to achieve the above object, the present invention provides a light-receiving element that outputs a current signal according to the amount of input light, a current-voltage converter that converts this current signal into a voltage signal, and the above voltage. A signal and a feedback signal are input and an amplitude limiter that outputs a binary signal whose amplitude is limited, and an input of this binary signal, the operating point of the amplitude limiter is the center point of the binary signal. A feedback circuit for outputting the feedback signal is provided.

With the above-described configuration, the present invention sets the comparison voltage at the time of binarization to the midpoint of the waveform, and the binarization operation by the binarization by the amplitude limiter is performed regardless of the reception amplitude. In addition, the duty ratio of the output waveform can be kept constant.

Example 1 FIGS. 1 and 2 show the configuration of an example of the present invention. In addition, in FIG. 1 and FIG.
The same reference numerals as those in the figure denote the same as those in FIG.

In FIGS. 1 and 2, 1 is a light receiving element, and 2
Is a current / voltage converter, 3 is an amplitude limiter, 21 is a feedback circuit, and includes an integrator 5 and an amplifier 6. Reference numeral 4 is a binary signal which is an output signal of the optical receiver. The anode terminal of the receiving element 1 is connected to the current / voltage converter 2, the output signal of the current / voltage converter 2 is input to the amplitude limiter 3, and the output signal of the amplitude limiter 3 is input to the integrator 5 and the optical signal. It is output as a binary signal 4 which is a receiver output signal. Furthermore, the integrator 5
Is output to the amplifier 6, and the output signal of the amplifier 6 is fed back to the amplitude limiter 3.

Next, the operation of the embodiment shown in FIGS. 1 and 2 will be described. In the above embodiment, the light receiving element 1 and the current
The operation of the voltage converter 2 is exactly the same as the conventional example. Electric current
The output signal of the voltage converter 2 is binarized by being subjected to amplitude limitation by the amplitude limiter 3 and output as a binary signal 4 which is an output signal of the optical receiver (see FIGS. 1 and 2). .

At this time, in the optical receiver shown in FIG. 2, the duty ratio of the binary signal 4 is detected by the integrator 5, and the operating point of the amplitude limiter 3 is set via the amplifier 6 so that this becomes a constant value. ing. By this operation, the duty ratio of the binary signal 4 is guaranteed to be constant even with respect to the received signal including waveform deterioration, so that the slice level at the time of binarization is automatically set.

As described above, according to the embodiments shown in FIGS. 1 and 2, since the amplitude limiter 3 performs binarization, there is an advantage that a response can be made at a high speed even when the light receiving level changes. In addition, according to the embodiment shown in FIG. 2, the slice level is automatically set so that the duty ratio of the binary signal 4 to be output is constant, and there is an effect that it is possible to perform no adjustment.

FIG. 3 shows a detailed configuration example of the amplitude limiter 3, the integrator 5, and the amplifier 6, which are the main parts of the embodiment shown in FIG. 2. In this embodiment, the amplitude limiter 3 and the amplifier 6 are used. The differential amplifiers 7, 8, 9 and the differential amplifier 14 are used, respectively, and the integrator 5 is an RC filter including resistors 10, 11 and capacitors 12, 13. Since the differential amplifier 9 is used
4,4 'binary signals of opposite phases are obtained. Further, in this embodiment, since the feedback circuit 21 has all linear characteristics, there is an effect that it is extremely easy to design and is stable.

Further, in the above embodiment, since the differential amplifier is used, there is an effect that the integration is easy. That is, as the differential amplifiers 7, 8, 9 and the amplifier 6, a line receiver IC which is an emitter-coupled logic element can be used.

The present invention is used for PCM digital optical transmission or the like, but may be used for pulsed analog transmission such as pulsed FM transmission. In this case, since the duty ratio of the output binary signal becomes constant, the effect of improving the distortion rate can be obtained.

Further, by adding the components as shown in FIG. 4 to the optical receiving apparatus (see FIGS. 1 to 3) according to the present invention, the binary clock 4 which is the output signal of the optical receiver is transmitted from the transmission clock. The signal can be extracted.

An embodiment in this case is shown in FIG. In FIG. 4, 22 is a code converter to which the binary signal 4 is input, 23 is a bandpass filter, and 24 is an extracted clock signal. The binary signal 4 which is the output signal of the optical receiver is code-converted by the code converter 22 and input to the bandpass filter 23. The output signal including the clock component extracted by the bandpass filter 23 is binarized again by the amplitude limiter 3, and the duty ratio of the clock signal 24 is controlled to be constant by the integrator 5 and the amplifier 6.

EFFECTS OF THE INVENTION The present invention, as is clear from the above embodiment, a light receiving element that outputs a current signal according to the amount of input light, a current-voltage converter that converts this current signal into a voltage signal, and the above voltage signal. An amplitude limiter that inputs a feedback signal and outputs a binary signal whose amplitude is limited, and the feedback that the operating point of the amplitude limiter is the center point of the binary signal when the binary signal is input. Since the configuration is such that a feedback circuit that outputs a signal is provided, as a result, the comparison voltage at the time of binarization is set at the midpoint of the waveform. The binary operation can be performed regardless of the above, and the duty ratio of the output waveform can be kept constant.

[Brief description of drawings]

1 and 2 are schematic block diagrams of an optical receiving device according to an embodiment of the present invention, and FIG. 3 is a circuit diagram of main parts of the device,
FIG. 4 is a schematic block diagram when the optical receiving device shown in FIGS. 1 to 3 is used for extracting a clock signal, and FIG. 5 is a schematic block diagram of a conventional optical receiving device. 1 ... Light receiving element, 2 ... Current / voltage converter, 3 ... Amplitude limiter, 4,4 '... Binary signal, 5 ... Integrator, 6 ... Feedback amplifier, 7,8,9 ... … Differential amplifier, 10,11 …… Resistance, 12,1
3 ... Capacitor, 14 ... Feedback amplifier, 21 ... Feedback circuit, 22 ... Code converter, 23 ... Band filter, 24 ... Clock signal.

Claims (4)

[Claims] 1. A light receiving element for outputting a current signal according to the amount of input light, a current / voltage converter for converting the current signal into a voltage signal, and the voltage signal and the feedback signal are input to limit the amplitude. And an amplitude limiter that outputs a binary signal
An optical receiver comprising a feedback circuit which receives a value signal and outputs the feedback signal in which the operating point of the amplitude limiter is the center point of the binary signal. 2. The amplitude limiter is a differential amplifier, and the feedback circuit includes an integrator connected to the differential amplifier, and an output signal of the integrator is amplified and fed back to the input side of the differential amplifier. The optical receiving device according to claim 1, wherein the optical receiving device is an amplifier. 3. The optical receiver according to claim 2, wherein the differential amplifier and the amplifier are emitter-coupled logic elements. 4. A light receiving element that outputs a current signal according to the amount of input light, a current / voltage converter that converts this current signal into a voltage signal, and a binary signal that limits the amplitude of the voltage signal and outputs a binary signal. A first amplitude limiter, a code converter for extracting a transmission clock from a binary signal, a bandpass filter, and a second amplitude limiter for binarizing an output signal from the bandpass filter,
An optical receiver comprising: a feedback circuit that applies negative feedback to the second amplitude limiter so that the operating point of the second amplitude limiter is set to the midpoint of the positive and negative peak values.