JPH0779257A - Signal receiving circuit device - Google Patents

Abstract

PURPOSE:To eliminate a feedback system, to make a circuit configuration simple and inexpensive, and to attain a highly precise operation without any adjustment at the time of receiving an optical signal, and converting it into a binary signal. CONSTITUTION:This device is provided with a pre-amplifier 2 which amplifies the received signal of the optical signal from an optical transmission line, an amplitude limiter 5 which amplitude-limits the output signal of the pre-amplifier 2 by a constant limit value, a comparator 6 which shreshold processes the output signal of the amplitude limiter 5 based on a certain threshold value, and a threshold value setting unit 7 which applies the threshold value to the comparator 6 so that an optimal S/N can be obtained based on the output signal of the amplitude limiter 5. That is, the pre-amplifier 2 amplifies the received current signal of the optical signal from the optical transmission line or the like, and converts it into a voltage signal, the amplitude limiter 5 amplitude-limits the output signal of the pre-amplifier 2 by the constant limit value, and when the comparator 6 binarizes the output signal of the amplitude limiter 5, the threshold value setting equipment 7 applies the threshold value so that the optimal S/N can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal receiving circuit device, and more particularly to a structure of an optical receiving circuit for receiving an optical signal having a wide dynamic range and converting it into a binary signal in high speed digital optical transmission. .

[0002]

2. Description of the Related Art Conventionally, as a signal receiving circuit device in high-speed digital optical transmission, for example, Japanese Patent Application Laid-Open No. 3-232 has been proposed.
Circuitry, such as that shown at 342, has been applied, as shown in the block diagram of FIG. In the figure, 1 is a light receiving element that receives an optical signal and generates a current signal corresponding to the received intensity, 2 is a preamplifier that amplifies and converts the current signal from the light receiving element 1 into a voltage signal, and 3 is a preamplifier. AGC (automatic gain control) that converts the output signal of the amplifier 2 into a binary signal of constant amplitude
The amplifiers 4 are peak detectors that detect the peak value of the output signal of the AGC amplifier 3 and control the gain of the AGC amplifier 3 so that it becomes a constant value.

The operation of the above-described structure will be described below.

The light receiving element 1 receives an optical signal from an optical transmission line (not shown) and generates a current signal according to the received intensity. The preamplifier 2 converts the current signal from the light receiving element 1 into a voltage signal.

The AGC amplifier 3 amplifies the voltage signal from the preamplifier 2 by variable gain so that its amplitude is constant. The peak detector 4 detects the peak value of the output signal of the AGC amplifier 3 and feeds it back to the AGC amplifier 3.
The AGC amplifier 3 changes its gain based on the feedback signal from the peak detector 4 and consequently controls the gain so that the peak value of its output signal becomes constant.

As a result, a binarized reception signal can be obtained by slicing the output of the AGC amplifier 3 with a constant threshold value.

[0007]

Since the conventional signal receiving circuit device is configured as described above, it is necessary to individually adjust the gain control of the AGC amplifier 3, which requires time. This leads to an increase in man-hours in mass production and an increase in cost.

The present invention has been made to solve the above-mentioned problems, and when receiving an optical signal and converting it into a binary signal, the desired operation is performed without adjustment. An object of the present invention is to provide a signal receiving circuit device capable of performing the above.

[0009]

To achieve the above object, the present invention provides a preamplifying means for amplifying a received signal of an optical signal from an optical transmission line or the like, and an output signal of the preamplifying means. Amplitude limiting means for limiting the amplitude with a fixed limit value, and an output signal of the amplitude limiting means based on a certain threshold value.
It is characterized by comprising: comparing means for digitizing; and threshold setting means for giving a threshold value to the comparing means based on the output signal of the amplitude limiting means so as to obtain an optimum S / N.

[0010]

In the above-mentioned means, the signal receiving circuit device of the present invention amplifies the received current signal of the optical signal from the optical transmission line or the like by the preamplification means and converts it into a voltage signal, and the preamplifier in the amplitude limiting means. Amplitude limiting is applied to the output signal of the amplifying means at a constant limit value, and when the output signal of the amplitude limiting means is binarized by the comparing means, the threshold setting means compares the output signal of the amplitude limiting means based on the output signal of the amplitude limiting means. A threshold value is given to the means so that the optimum S / N can be obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1. First Embodiment FIG. 1 is a block diagram of a signal receiving circuit device according to a first embodiment of the present invention, and particularly illustrates the configuration of a 2R receiver. In the figure, 5 is
Amplitude for limiting the amplitude to a certain limit value by inputting the signal from the preamplifier 2 that converts the signal from the light receiving element 1 that receives the optical signal and generates the current signal according to the light intensity into the voltage signal. A limiter, 6 is a comparator for slicing the output signal of the amplitude limiter 5 at a certain threshold value and converting it into a binary signal,
Reference numeral 7 is a threshold value setting device that gives a threshold value to the comparator 6 so that an optimum S / N can be secured, depending on the level of the output signal of the amplitude limiter 5.

The operation of the above-described structure will be described below.

The light receiving element 1 receives an optical signal from an optical transmission line (not shown) and generates a current signal according to the received intensity. The preamplifier 2 converts the current signal from the light receiving element 1 into a voltage signal.

When the level of the voltage signal from the preamplifier 2 exceeds a certain limit value, the amplitude limiter 5 suppresses the level to the limit value and outputs it.

The output of the amplitude limiter 5 is given to the threshold value setting device 7. The threshold value setting device 7 responds to the level of the output signal of the amplitude limiting device 5, that is, the comparator 6. The threshold value given to S / at the input of the comparator 6
Change so that N is optimal.

The output of the amplitude limiter 5 is compared with the threshold value from the threshold value setting device 7 in the comparator 6, converted into a binary signal, and output.

As a result of the above operation, the comparator 6 has a threshold value corresponding to the level of the output signal of the amplitude limiter 5,
Since the output of the amplitude limiter 5 is binarized, the received signal can be set to the optimum point without adjustment regardless of the level of the optical signal received by the light receiving element 1.

That is, the amplitude limiter 5 outputs the output signal of the preamplifier 2 as a signal suitable for binarization, but the gain amount which is insufficient in the preamplifier 2 and the amplitude limiter 5 is compensated by the comparator 6. . In this case, the S / N at the input of the comparator 6 is optimized by setting the threshold value given to the comparator 6 by the threshold value setting unit 7 based on the output of the amplitude limiter 5.

As a result, the reception level of the signal received by the light receiving element 1 is binarized through the limiting function of the amplitude limiter 5 and the binarizing function of the comparator 6, so that the speed is high and stable. It is possible to perform a binarization operation. Further, since the operating point of the comparator 6 is adjusted to the optimum S / N point of the output of the amplitude limiter 5, the slice level at the time of binarization is set to the optimum point without adjustment.

Example 2. Second Embodiment FIG. 2 is a block diagram of a signal receiving circuit device according to a second embodiment of the present invention, and particularly illustrates the configuration of a 3R receiver. In the figure, 8 is a clock generator that generates a clock signal based on the binary signal output of the comparator 6, and 9 is a flip-flop that latches the output of the comparator 6 based on the clock from the clock generator 8. It is 9.

Next, the operation of the above-described structure will be described.

The optical signal received by the light receiving element 1 is compared with the comparator 6
The configuration is exactly the same as that of FIG. 1 until the signal is converted into a binarized signal by. Now, the clock generator 8 generates a clock signal for self-clocking based on the binarized signal from the comparator 6. This is performed by locking the phase and frequency of the free-running clock on the periodic component of the binarized signal obtained by the comparator 6.

Next, based on the clock signal obtained by the clock generator 8, the output signal of the comparator 6 is latched by the flip-flop 9 so that a binarized signal with stable time axis can be obtained.

On the other hand, by supplying the clock from the clock generator 8 to the system side which processes this binarized signal, the subsequent signal processing can be performed with the common clock.

[0026]

As described above, according to the present invention, the amplitude of the received signal is limited, and the lack of gain due to the amplitude limitation is binarized by the comparator by the threshold value based on the amplitude limited signal. There is an effect that the feedback system is eliminated, the circuit configuration is simple and inexpensive, and highly accurate operation can be performed without adjustment.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal receiving circuit device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a signal receiving circuit device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional signal receiving circuit device.

[Explanation of symbols]

 1 light receiving element 2 preamplifier 3 AGC amplifier 4 peak detector 5 amplitude limiter 6 comparator 7 threshold value setter 8 clock generator 9 flip-flop

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04B 10/26 10/14 10/04 10/06

Claims (1)

[Claims] 1. Preamplifying means for amplifying a received signal, amplitude limiting means for limiting the amplitude of the output signal of the preamplifying means, comparing means for binarizing the output signal of the amplitude limiting means, and A threshold value setting means for applying a threshold value to the comparing means based on the output signal of the amplitude limiting means.