JPS60250730A - Optical receiver - Google Patents

Abstract

PURPOSE:To increase the minimum receiving level and to remove malfunction at the variation of power supply voltage and temperature by changing the clamping level of a threshold voltage similarly to the operation point of an amplifier at the variation of the power supply voltage and temperature. CONSTITUTION:A digital signal obtained by converting an optical signal into an electric signal by a photodetector 1 in an optical receiver is amplified by an amplifier 2 and its output is inputted to a threshold setting circuit 3 and one input of a comparator 4. A photodetector 5 converts DC light obtained from a light emitting element 8 to be emitted by a driving circuit 7 into a digital signal and applies the digital signal to the setting circuit 3 through an amplifier 6. A distance between the light emitting element 8 and the photodetecting element 6 or the output power of the light emitting element 8 is set up to set up the signal amplified by the amplifier 6 slightly larger than the signal amplified by the amplifier 2. The clamping level of the threshold voltage of the comparator 4 is set up in a setting circuit 3 so as to be changed similarly to the variation of the power supply voltage and temperature. Thus, the minimum receiving level is prevented from being increased and the device is prevented from malfunction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical receiver that receives digital optical signals.

[Background technology]

In an optical receiver that receives a digital μ optical signal,
Since the received waveform becomes dull and the human power level changes depending on the length of the optical fiber, etc., if the threshold value is fixed when reproducing the waveform, the bus width of the output signal to be reproduced will vary depending on the input V and ρ. will recoil. Therefore, a method is used that includes an automatic threshold setting circuit that automatically adjusts the threshold according to the input level. In an optical receiver equipped with the above automatic threshold setting circuit, after amplifying the output signal of the light receiving element, peak detection is performed, and as shown in Figure 1, half of the above peak value is detected by the comparator. The threshold value is equalized to a certain level μ to prevent the comparator from malfunctioning due to noise or the like when there is no optical signal. The minimum received light power that can accurately reproduce pulses is determined by the above-mentioned Kufunfu level, but in the past, this Kufunfu level p was determined by inputting a minute signal into a reference voltage circuit or an amplifier with the same configuration as the received signal amplifier. , or set the operating point at a higher voltage, etc. However, in the above-mentioned setting method, the clamp Vbe is not exactly the same as the operating point of the receiving signal amplifier with respect to power supply voltage fluctuations and temperature fluctuations. This has disadvantages such as an increase in the minimum light reception level and malfunctions due to the fluctuation.

[Purpose of the invention]

The present invention has been made to improve the above points, and its purpose is to provide an optical receiver that does not increase the minimum light receiving level 'μ or malfunction due to fluctuations in power supply voltage or temperature. It is about providing.

[Disclosure of the invention]

The present invention will be explained below based on the drawings shown as examples.

FIG. 2 is a block diagram of an optical receiver according to an embodiment of the present invention.

The digital optical signal converted into an electric signal by the light receiving element 1 is amplified by the amplifier 2, and its output is sent to the threshold setting circuit 3.
is input to the comparator 4 at the subsequent stage. The output of an amplifier 6 that amplifies the output of the light receiving element 5 is also input to the threshold setting circuit, and the monthly value of the peak value of the output of the amplifier 2 is outputted as a comparison voltage of the comparator 4. The above output is
The output value of the amplifier 6 is multiplied by 1. A drive circuit 7 inputs DC light from a light emitting element 8 that emits DC light to the light receiving element 5 . The amplifier 6 and the light receiving element δ have the same configuration as the SUa intensifier 2 and the light receiving element 1, respectively. If the distance between the light emitting element 8 and the light receiving element 5 or the output optical power of the light emitting element 8 is set so that the light input to the light receiving element δ becomes minute, when there is no digital optical signal, The output of amplifier 6 is slightly higher than the output of amplifier 2.

According to the optical receiver having the above configuration, the Kutsune level ρ of the threshold setting circuit 3 is set by the light receiving element 5 and the amplifier 6, which have the same configuration as the light receiving element 1 and the amplifier 2, which receive and amplify the digital optical signal. Therefore, with respect to power supply voltage fluctuations and temperature fluctuations, the quorum varies in the same way as the operating point of the amplifier 2, so the minimum light reception level determined by the kufunlev does not increase and no malfunction occurs.

FIG. 3 shows an optical receiver configured such that the optical receiver drive circuit 7 is controlled by a noise level detection circuit 9. In FIG. 10 is a shielding case, and U is a noise detection antenna. The noise level detection circuit 9 detects the surrounding noise level, and controls the light emitting power of the light emitting element 80 depending on the magnitude of the noise level. That is, in a bad noise environment, by increasing the light emitting power of the light emitting element 8 and increasing the noise level of the threshold setting circuit 3, malfunctions due to noise can be prevented.

〔Effect of the invention〕

As described above, according to the present invention, a light receiving element converts an optical input signal into an electrical signal, an amplifier amplifies the output of the light receiving element, and a threshold voltage is set depending on the output of the amplifier. In an optical receiver consisting of a threshold setting circuit and a comparator that compares the output of the amplifier with the threshold voltage, the clamping level ρ of the threshold voltage is adjusted as described above in response to power supply voltage fluctuations and temperature fluctuations. Since it is made to fluctuate in the same way as the operating point of the amplifier, -
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[System] Age H1 HFP E was provided by TILL KAIKI.

[Brief explanation of the drawing]

1(b) is a received signal waveform, FIG. 2 is a block diagram of the first embodiment of the present invention, and FIG. 3 is a block diagram of the second embodiment of the present invention. FIG. 2 is a block diagram according to an embodiment. Patent applicant Matsushita Electric Works Co., Ltd. Patent attorney Toshimaru Takemoto (and 2 others) Figure 1 Figure 2 Figure 3 Figure 1

Claims (1)

[Claims] tlJ a light receiving element that converts an optical input signal into an electrical signal;
The light receiving element comprises an amplifier that amplifies the output of the light receiving element, a threshold setting circuit that sets a threshold voltage based on the output of the amplifier, and a comparator that compares the output of the amplifier with the threshold voltage. In the receiver, a means for emitting minute light, a light receiving element having the same configuration as the light receiving element and receiving the minute light, and an amplifier having the same configuration as the amplifier and amplifying the output of the light receiving element, An optical receiver characterized in that the quanglepe of the threshold voltage is set by the output of the amplifier. .