JPH0449739A - Optical receiver - Google Patents

Abstract

PURPOSE:To obtain a satisfactory threshold voltage without being affected by the fluctuation of temperature and a source voltage and to dispense with adjustment for an external threshold value by providing a threshold value generation circuit between the positive phase signal and the negative phase signal of the output of a light receiving amplifier circuit. CONSTITUTION:A received optical signal is converted to a current by a photodetector 1, and an electrical signal is outputted differentially as an output DC offet voltage, a positive phase side output signal, and a negative phase side output signal by the light reception amplifier circuit 2. When the resistance values of a resistor 10 and a resistor 11 comprising the threshold value generation circuit 9 are set at the same resistance values, a voltage Vref generated from the connection point of the resistors 10, 11 goes to the 1/2 of the sum of a positive phase side DC voltage V2 and a negative phase side DC voltage V1, thereby, the optimum threshold voltage with amplitude of half the output amplitude can always be generated. Thereby, it is possible to obtain the satisfactory threshold voltage not being affected by the fluctuation of the temperature and the source voltage, and also, to dispense with the adjustment for the external threshold value at every time of manufacturing, and to reduce a production cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical receiver, and particularly to an optical receiver equipped with a threshold value generation circuit.

[Conventional technology]

An example of a conventional optical receiver is shown in FIG. 3 and will be described.

This FIG. 3 can be seen, for example, in the literature
“170 Mbit/s T-R” by gsml et al.
Integrated Opticml Concept
s J FOC/LAN'87&MFOC-WEst
, P167 to P170), in which 1 is a light receiving element that converts a received optical signal into an electrical signal, 21d is an offset between a normal phase signal and a negative phase signal corresponding to the received optical signal. 3 is a timing extraction circuit that extracts a timing component corresponding to the bit rate of the received signal from the output of the light reception amplifier circuit 2; 4 is this timing extraction circuit 3;
an identification circuit that performs synchronous reproduction of a received signal using the output of the 5
is the dark value input voltage terminal (Vthx) of this identification circuit 4, 6
is the dark value input voltage terminal (Vthz
), 1 is an output terminal from which a signal is sent, and an output terminal from which an 8Fi clock is sent. Further, DT and DT indicate data (signal), and CLK indicates a clock.

Next, the operation of the optical receiver shown in FIG. 3 will be explained.

First, the received multiplication table signal is converted into a smudge signal by the light receiving element 1, and the electrical signal is output by the light receiving amplifier circuit 2. is output.

Next, the positive phase and negative phase of the output signal of the light receiving amplification circuit 2 are input to the identification circuit 4 and the timing extraction circuit 3 on one side, respectively, and the threshold voltage input terminal 5 of the identification circuit 4 and the dark value of the timing extraction circuit 3 A dark value voltage is applied to the voltage input terminal 6 from the outside. Then, the signal is extracted from the input signal, the signal is identified and reproduced, and the signal is output to the output terminal 7.
A clock is output to each output terminal 8.

[Problem to be solved by the invention]

In conventional optical receivers such as those described above, the DC level of the signal input to the identification circuit and timing extraction circuit changes due to changes in temperature and power supply voltage, and the voltage applied from the outside may not be the optimal value. There was a problem that reception characteristics deteriorated.

In addition, there is a problem in that the external threshold value needs to be adjusted every time it is manufactured, which increases production costs.

This invention was made in order to solve these problems, and it is possible to obtain a good threshold voltage that is not affected by temperature or power supply voltage fluctuations, and it also eliminates the need for external threshold adjustment every time it is manufactured, resulting in a low production cost. The purpose is to obtain equipment.

[Means to solve the problem]

An optical receiver according to the present invention includes: a light receiving element that converts a received optical signal into an electrical signal; a light receiving amplifier circuit having a function of maintaining constant offset voltages of a normal phase signal and a negative phase signal corresponding to the received optical signal; The output of this light receiving amplifier circuit is composed of a timing extraction circuit that extracts a timing component corresponding to the pit rate of the received signal, and an identification circuit that performs synchronous reproduction of the received signal using the output of this timing extraction circuit. In the receiving device, a first resistor and a second resistor are connected in series between the positive phase signal and the negative phase signal of the output of the light receiving amplifier circuit.
GND from the connection point between the resistor and the first and second resistors.
It is equipped with a threshold generation circuit consisting of K-connected capacitors.

[Effect]

In this invention, the dark value generation circuit is connected between the positive phase signal and the negative phase signal of the output of the light receiving amplifier circuit, which has the function of keeping constant the offset voltage of the positive phase signal and negative phase signal corresponding to the received optical signal. By providing this, a good rAfE voltage that is not affected by temperature or power supply voltage fluctuations can be obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing an embodiment of an optical receiver according to the present invention.

In FIG. 1, the same reference numerals as in FIG.
．． This is a dark value generation circuit consisting of a capacitor 12 connected to GND K from a connection point of 11.

V r e f indicates the voltage generated at the connection point of the resistor 10.11.

FIG. 2 is an explanatory diagram showing the output voltage waveform of the light receiving and amplifying circuit in FIG. 1. In the figure, 13 is a positive phase side output signal, and 14 is a negative phase side output signal.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIG. 2.

First, the received optical signal is converted into a spot signal by the light receiving element 1, and the electric signal is converted to an output DC by the light receiving amplifier circuit 2.
A positive phase side output signal 13 and a negative phase side output signal 14 having the same offset voltage and voltage amplitude (V) shown in FIG. 2 are differentially output. Here, the positive phase side DC voltage of this output signal is
, the negative phase side DC voltage is v2, and the low level of the positive phase side output signal 13 is v2. The high level of the negative phase side output signal 14 is assumed to be VH (=VI, ). Also, if the mark rate of the signal is m, the positive phase side DC voltage v1 of the output signal is V I = V (
,, + m・Δ■, reverse phase reverse phase side DC voltage upper 22 = VL
+(1m) ・AV Te is expressed.

A resistor 10 and a resistor 11 forming the dark value generating circuit 9
Assuming that are resistances of the same value, the voltage vref generated at the connection point of the resistor 1011 is 1/2 of the sum of the positive-phase side DC voltage v1 and the negative-phase side DC voltage v2, so Vr, f = VL+ 1
/2·ΔV, and the optimal dark value voltage, which is half the output amplitude, is always generated.

Next, the dark value voltage generated in this way is sent to the identification circuit 4 and the timing extraction circuit 3K in the same way as above.

One side of the differential output signal of the light receiving amplifier circuit 2 and the dark value voltage are respectively passed. Then, the timing extraction circuit 3 extracts the clock, and the identification circuit 4 identifies and reproduces the received signal using the extracted clock.
A clock is output to each output terminal 8.

〔Effect of the invention〕

As explained above, this invention has a function of keeping the offset voltage of the normal phase signal and the negative phase signal corresponding to the received optical signal at one level. By providing a threshold generation circuit with two resistors and one capacitor, it is possible to obtain a good threshold voltage that is not affected by temperature or power supply voltage fluctuations. Also,
This has the effect that it is possible to realize an optical receiving device with low production cost since there is no need to adjust the external l value every time it is manufactured.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an optical receiving device according to the present invention, FIG. 2 is an explanatory diagram showing an output voltage waveform of the light receiving amplification circuit in FIG. 1, and FIG. 3 is an example of a conventional optical receiving device. FIG. 1...Light receiving confectionery, 2-#--Light receiving amplification circuit, 3--timing extraction circuit, 4...-〇 identification circuit, 9--Threshold generation circuit, 10.11--... Resistance, 12. Capacity.

Claims (1)

[Claims] A light-receiving element that converts a received optical signal into an electrical signal, a light-receiving amplifying circuit having a function of keeping constant the offset voltage of a positive-phase signal and a negative-phase signal corresponding to the received optical signal, and an output of this light-receiving amplifying circuit. In an optical receiver comprising a timing extraction circuit that extracts a timing component corresponding to the bit rate of a received signal, and an identification circuit that performs synchronous reproduction of the received signal using the output of this timing extraction circuit,
It consists of a first resistor and a second resistor connected in series between the positive phase signal and the negative phase signal of the output of the light receiving amplifier circuit, and a capacitor connected to GND from the connection point of the first and second resistors. An optical receiver comprising a threshold generation circuit.