JPH0620190B2 - Optical signal receiving circuit - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an optical signal receiving circuit for receiving optical signals in a burst configuration which are periodically transmitted from a plurality of optical signal transmitting devices in a predetermined order. Is.

[Technical background of the invention]

In recent years, a plurality of data processing devices have been installed within a certain limited range, and mutual data communication is performed between the processing devices by optical signals, thereby improving the efficiency of data processing. Has been put to practical use.

In such a system, an optical signal for data communication undergoes modulation such as FSK modulation and is transmitted as an optical signal having a burst structure, and is further periodically transmitted in a predetermined order.

Therefore, an optical signal receiving circuit as shown in FIG. 3 or FIG. 4 has been conventionally used for the device on the side receiving such an optical signal.

That is, the optical signal receiving circuit shown in FIG. 3 receives the optical signal PH by the photodiode 1, inputs the output signal of the photodiode 1 into the amplifier 3 via the capacitor 2 for removing the DC component, and amplifies it by the amplifier 3. After that, it is sent to a required circuit section. In addition, the optical signal receiving circuit shown in FIG. 4 has a peak value detection circuit 4 and a DC amplifier 5 added to the configuration of FIG. 3, detects the peak of the output signal level of the amplifier 3, and detects this peak value. Accordingly, the gain of the amplifier 3 is adjusted by the DC amplifier 5 so that the output signal level of the amplifier 3 is kept substantially constant.

[Problems of background technology]

However, in the conventional circuits shown in FIGS. 3 and 4, since the DC component removing capacitor 2 is connected to the input of the amplifier 3, there is a difference in the DC level of the optical signals received from the plurality of transmission sources. In some cases, a transient current flows in the capacitor 2 when an optical signal of a different DC level is received, and the amplifier 3
There is a problem in that the output signal of is distorted. Also,
In the conventional circuit shown in FIG. 4 for adjusting the gain of the amplifier 3, it takes time for the output signal level of the amplifier 3 to stabilize due to the response delay of the peak value detection circuit 4 and the DC amplifier 5, and in particular, the transmission source When the DC level of the optical signal differs for each, there is a problem that it becomes difficult to decode the output signal of the amplifier 3.

[Object of the Invention]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide an optical signal receiving circuit capable of stably receiving an optical signal of a burst structure that periodically arrives without distortion.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention receives a burst-structured optical signal periodically generated from a plurality of optical transmission sources in a predetermined order by a light receiving element, and uses an output of the light receiving element as a capacitor. In an optical receiving circuit for obtaining an output signal from the amplifier by averaging an output signal level of the light receiving element, and an output of the averaging circuit for each of the optical signals having the burst configuration. An analog-digital converter that converts a digital value at the timing of a burst, a storage circuit that sequentially stores the output of the analog-digital converter, and a digital value corresponding to each burst stored in the storage circuit that has the burst configuration. The digital value is read in the next cycle of the signal, and the digital value of the bias voltage of the capacitor at the time of receiving each burst of the optical signal having the burst configuration Into an analog signal for controlling the gain of the fine said amplifier characterized by comprising a digital Ana b converter applied to the capacitor and the amplifier.

Example of Invention

 Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the photodiode 1, FIG. 2 (b) is provided at every cycle T shown in FIG. 2 (a).
An optical signal PH having a burst structure at times T ₁ , T ₂ , and T ₃ as shown in ( ₁₎ is input. The optical signal PH is converted into an electric signal by the photodiode 1, and the output signal of the photodiode 1 is input to the amplifier 3 via the DC removing capacitor 2 as in the conventional case. At the same time, the average value signal (integrated signal) of the output signal level is formed by being input to the averaging circuit (integrating circuit) including the resistor 7 and the capacitor 8 via the buffer amplifier 6. As a result, when the optical signal PH of the level shown in FIG. 2 (b) arrives, an average value signal (integrated signal) as shown in FIG. 2 (c) is formed.

This average value signal is input to the AD converter 9, and the timing generator 10 outputs the time Tn (n = n) as shown in FIG.
1, 2, 3) are converted into digital values by the timing signals generated. Then, the digital value is stored in the memory 11 at a timing synchronized with the timing signal generated from the timing generator 10.

The digital value stored in the memory 11, that is, the average value of the optical signal is the timing signal generated from the timing generator 10 at the start timing of receiving the optical signal of each burst of the next period of the optical signal having the burst structure of the period T. Is read out and supplied to the DA converters 12 and 13. Then,
The DA converter 12 converts the digital value corresponding to each burst read from the memory 11 into an analog signal corresponding to this digital value, and supplies this analog signal as a gain adjustment signal for the amplifier 3. Similarly, the DA converter 13 also converts the digital value corresponding to each burst read from the memory 11 into an analog signal corresponding to this digital value, and this analog signal is passed through the resistor 14 to the capacitor 2
Is supplied as a bias potential signal.

For example, when the photodiode 1 receives from the DA converter 13 an optical signal having a burst structure with a period T as shown in FIG.
An analog signal whose level is inversely proportional to the magnitude of the average level of each burst is output as shown in FIG. 7E, and this analog signal is applied to the capacitor 2 as a bias potential, whereby the bias potential of the capacitor 2 is changed. It is adjusted for each burst of the optical signal of the burst configuration.

By adjusting the bias potential of the capacitor 2, a transient waveform A generated by the difference in the DC level of each burst as shown in FIG.
The capacitor 2 outputs a signal with a uniform DC level as shown in FIG. 2 (f), and this signal with a uniform DC level is input to the amplifier 3.

Similarly to the waveform shown in FIG. 2E, the DA converter 12 also outputs an analog signal in which each level is inversely proportional to the average level of each burst, and this analog signal is gained to the amplifier 3. It is added as an adjustment signal. Thereby, the gain of the amplifier 3 is adjusted corresponding to each burst of the optical signal having the burst structure.

By adjusting the gain of the amplifier 3, the signal level of each burst is adjusted, and a stable output signal having a uniform signal level as shown in FIG. 2 (g) can be obtained.

Here, the switching of the bias potential of the capacitor 2 and the switching of the gain of the amplifier 3 are digitally performed corresponding to the values detected corresponding to each burst of the previous cycle of the optical signal having the Bartho structure, so that it is instantaneous. Can be switched,
Continuous AGC control becomes possible corresponding to each burst.

As described above, in this embodiment, even if the DC level of the optical signal that periodically arrives is different, the received output of the optical signal having a stable level without distortion can be transmitted. Further, since the bias potential of the capacitor 2 and the gain of the amplifier 3 are adjusted in accordance with the average level of each burst in the previous cycle of the optical signal having the burst structure, it is caused by the delay in response of the gain adjustment as in the conventional case. Problems can be resolved.

Since the DA converters 12 and 13 in the embodiment both output a signal that is inversely proportional to the average value of the optical signal of the previous cycle, one of the output signals is divided by a resistor or the like to generate the capacitor 2 The other can be omitted by applying the bias potential and the gain adjustment signal of the amplifier 3.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, it is possible to send an optical signal of a burst structure that periodically arrives as a reception output of a stable level without distortion, and in fact, to obtain a dynamic range of the reception signal. There is an effect that it can be expanded. Therefore, when it is applied to various optical communication systems which receive optical signals from N optical transmission sources and perform communication, an extremely excellent effect is exhibited.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
FIGS. 3 and 4 are diagrams showing the output waveform of each part in the circuit of the figure, and are diagrams showing the configuration of a conventional optical signal receiving circuit. 1 ... photodiode, 2 ... capacitor, 3 ... amplifier, 8 ... capacitor, 9 ... AD converter, 11 ... memory, 12,13 ... DA converter.

Claims (1)

[Claims] 1. A light receiving element receives an optical signal of a burst structure which is periodically generated from a plurality of optical transmission sources in a predetermined order, and the output of the light receiving element is input to an amplifier via a capacitor. An optical signal receiving circuit for obtaining an output signal from the amplifier, an averaging circuit for averaging the output signal level of the light receiving element, and an output of the averaging circuit for digitalizing the output of the burst configuration at each burst timing An analog-digital converter for converting the value into a value, a storage circuit for sequentially storing the output of the analog-digital converter, and a digital value corresponding to each burst stored in the storage circuit for the next cycle of the optical signal having the burst configuration. And the digital value is read by the bias potential of the capacitor and the amplifier at the time of receiving each burst of the optical signal having the burst configuration. An optical signal receiving circuit, comprising: a digital-to-analog converter which converts an analog signal for controlling gain and adds the analog signal to the capacitor and the amplifier.