JPH05102744A - Optical reception circuit for ternary apd - Google Patents

Abstract

PURPOSE:To apply automatic control to the ternary APD so that the multiplication factor is not much decreased because the band width is rapidly reduced when the multiplication factor of the ternary APD is too much decreased. CONSTITUTION:An optical signal to be inputted is converted into an optical current signal by a ternary APD 1, subject to current voltage conversion by a preamplifier circuit 2, amplified by an equalization amplifier circuit 3, a high frequency component in an output signal of the equalization amplifier circuit 3 is extracted by a high pass filter 4 and a peak detection circuit 5 detects a peak level of a high frequency signal. A reverse bias control circuit 6 controls a reverse bias application circuit 7 so that the detected peak signal is less than a set threshold level thereby preventing the multiplication factor M of the ternary APD 1 from being much decreased. Thus, it is not required to make adjustment in matching with each characteristic of the ternary APD, the man-hour is reduced and even when the characteristic of the ternary APD is subject to secular change, since automatic control is always applied, the deterioration in the dynamic range of the optical receiver is not deteriorated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver circuit, and more particularly to an optical receiver circuit using a ternary APD.

[0002]

2. Description of the Related Art First, characteristics of a ternary (InGaAs) APD will be described. The ternary APD has a smaller excess noise figure than Ge-APD, and can realize high sensitivity of the receiver. However, as shown in FIG. 2, the multiplication factor becomes small, and when Mmin is divided, the band has a drawback that it is rapidly deteriorated.

Next, a conventional optical receiving circuit will be described with reference to FIG. The conventional optical receiver circuit includes a ternary APD 1 for photoelectric conversion and a preamplifier circuit 2 for converting photocurrent into a voltage signal.
And an equalizing amplifier circuit 3 for equalizing and amplifying its output, and a ternary AP
It has a reverse bias application circuit 7 for applying a reverse bias to D and a reverse bias control circuit 6 for controlling the reverse bias voltage according to the received light power of the ternary APD. The reverse bias control circuit 6 operates to decrease the multiplication factor M of the ternary APD as the received light power increases, that is, to decrease the reverse bias voltage. Therefore, when the received light power becomes large, the multiplication factor M becomes too small, and the band may deteriorate rapidly. Therefore, the reverse bias voltage is limited so that the multiplication factor M does not fall below the lower limit in accordance with the characteristics of the APD. I'm adjusting to call.

[0004]

However, in the conventional optical receiving circuit, it is necessary to adjust the characteristics according to the individual characteristics of the ternary APD, which requires a lot of man-hours.
When the characteristic of D changes, there is a problem that the dynamic range of the optical receiver deteriorates.

An object of the present invention is to extract a high frequency component of an equalized amplified signal and automatically control the multiplication factor of the ternary APD so that the peak value of the amplitude does not fall below a set threshold value. To provide.

[0006]

The optical receiving circuit for ternary APD according to the present invention includes a ternary APD that photoelectrically converts an optical signal to output a current signal, and a current-voltage conversion of the current signal into a voltage signal. A preamplifier circuit for outputting, an equalizing amplifier circuit for equalizing and amplifying the voltage signal, a high-pass filter for taking out only a high frequency component from the equalized and amplified signal, and a peak detection circuit for detecting a peak of the high frequency component. And a reverse bias control circuit that controls the reverse bias voltage according to the peak signal, and a reverse bias application circuit that applies the reverse bias voltage to the ternary APD.

[0007]

The present invention will be described below with reference to the drawings. FIG. 1 is a configuration block diagram of the present invention. The present invention is
It comprises a ternary APD 1, a preamplifier circuit 2, an equalizing amplifier circuit 3, a high-pass filter 4, a peak detection circuit 5, a reverse bias control circuit 6, and a reverse bias application circuit 7. The input optical signal is converted into a photocurrent signal by the ternary APD 1, further converted into a voltage signal by the preamplification circuit 2, and then equalized and amplified by the equalization amplification circuit 3. Further, the reverse bias application circuit 7 applies a reverse bias voltage to the ternary APD 1. The reverse bias control circuit 6 is normally a ternary APD1.
As the received light power of 1 increases, the multiplication factor M of the ternary APD 1 is lowered, that is, the reverse bias voltage is lowered.

FIG. 2 shows the relationship between the multiplication factor M and the band of the ternary APD. Generally, in APD, the product of the multiplication factor M and the band is constant, so that the band gradually decreases as the multiplication factor M increases, but in the case of the ternary APD, if the multiplication factor M becomes too small (M <Mmin ) It has the characteristic that the bandwidth drops sharply. The NRZ equalization amplification waveform when the multiplication factor M of the ternary APD is changed is shown in FIG. Gain M is Mmi
If it is in the range of n to Mmax, the eye is sufficiently open as shown in (a), but if it is less than Mmin, the eye is closed due to insufficient band.

That is, when the received light power of the ternary APD becomes large and the multiplication factor M becomes smaller than Mmin, the amplitude of the high frequency component in the output signal of the equalizing and amplifying circuit 3 decreases. Therefore, the high-pass filter 4 takes out the high-frequency component, the peak detection circuit 5 detects the peak of the amplitude of the high-frequency component, and when the peak value becomes less than the threshold value, the multiplication factor M of the ternary APD is increased. The reverse bias control circuit 6 controls the reverse bias application circuit.

[0010]

As described above, according to the present invention, the high frequency component of the equalized and amplified signal is extracted, and the multiplication factor of the ternary APD is automatically adjusted so that the peak value of the amplitude does not fall below the set threshold value. Control so that each APD
Since there is no need to make adjustments in accordance with the characteristics of (1), the number of steps can be reduced, and the dynamic range of the optical receiver does not change even if the characteristics of the APD change over time.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of the present invention.

FIG. 2 is a graph showing the relationship between the multiplication factor M of ternary APD and the band.

FIG. 3 is an NRZ equalized amplification waveform when the multiplication factor M of the ternary APD is changed.

FIG. 4 is a configuration diagram of a conventional optical receiver circuit.

[Explanation of symbols]

 1 3-element APD 2 Preamplification circuit 3 Equalization amplification circuit 4 High-pass filter 5 Peak detection circuit 6 Reverse bias control circuit 7 Reverse bias application circuit

Claims (1)

[Claims] 1. A ternary APD for photoelectrically converting an optical signal to output a current signal, a preamplifier circuit for current-voltage converting the current signal and outputting a voltage signal, and an equalizing and amplifying the voltage signal. Equalizing and amplifying circuit, a high-pass filter for extracting only high frequency components from the equalized and amplified signal, a peak detecting circuit for detecting a peak of the amplitude of the high frequency components, and a reverse bias voltage controlled according to the peak signal. A reverse bias control circuit; and a reverse bias application circuit for applying a reverse bias voltage to the ternary APD.
Original APD optical receiver circuit.