JP3114821B2 - Optical receiver circuit for ternary APD - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiving circuit, and more particularly to an optical receiving 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 the Ge-APD, and can realize higher sensitivity of the receiver. However, as shown in FIG. 2, there is a disadvantage that the multiplication factor becomes small, and when Mmin is divided, the band is rapidly deteriorated.

Next, a conventional optical receiving circuit will be described with reference to FIG. A conventional optical receiving circuit includes a ternary APD 1 for photoelectric conversion and a preamplifier circuit 2 for converting a photocurrent into a voltage signal.
And an equalizing amplifier circuit 3 for equalizing and amplifying the output, and a three-way 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 a 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 is increased, the multiplication factor M becomes too small, and the band may be rapidly deteriorated. Adjusted to put on.

[0004]

In the conventional optical receiving circuit, it is necessary to perform adjustment 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.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ternary APD optical receiving circuit for automatically controlling a multiplication factor of a ternary APD so that a high-frequency component of an equalized amplified signal is extracted and a peak value of the amplitude does not fall below a set threshold value. Is to provide.

[0006]

In order to achieve the above object , an optical receiving circuit for ternary APD according to the present invention comprises: a ternary APD for photoelectrically converting an optical signal to output a current signal; A preamplifier circuit for converting a voltage and outputting a voltage signal, an equalizing amplifier circuit for equalizing and amplifying the voltage signal, a high-pass filter for extracting only a high-frequency component of the equalized and amplified signal, and the high-frequency component A peak detection circuit for detecting the peak of the amplitude of the ternary APD, and a reverse bias voltage to the ternary APD.
A reverse bias application circuit for applying a voltage, and the peak detection circuit
If the peak value detected by
In order to increase the multiplication factor of the three-way APD,
Reverse bias voltage for controlling the reverse bias voltage of the bias application circuit
And a pressure control circuit .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a configuration block diagram of the present invention. The present invention
It comprises a ternary APD 1, a preamplifier circuit 2, an equalization 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 preamplifier circuit 2, and then equalized and amplified by the equalization amplifier circuit 3. The reverse bias application circuit 7 applies a reverse bias voltage to the ternary APD 1. The reverse bias control circuit 6 normally includes the three-way APD 1
As the received light power becomes larger, the multiplication factor M of the ternary APD 1 is reduced, that is, the reverse bias voltage is reduced.

FIG. 2 shows the relationship between the multiplication factor M of the ternary APD and the band. In general, since the product of the multiplication factor M and the band is constant in the APD, the band gradually decreases as the multiplication factor M increases. However, in the case of the ternary APD, when the multiplication factor M is too small (M <Mmin ) The characteristic is that the bandwidth is sharply reduced. FIG. 3 shows an NRZ equalization amplification waveform when the multiplication factor M of the ternary APD is changed. Multiplication factor M is Mmi
If it is in the range of n to Mmax, the eye is sufficiently open as in (a), but if it is less than Mmin, the eye is closed due to lack of bandwidth.

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 amplifier 3 decreases. Then, the high-frequency component is extracted by the high-pass filter 4, the peak of the amplitude of the high-frequency component is detected by the peak detection circuit 5, and when the peak value becomes equal to or 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 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. , So each APD
This eliminates the need for adjustment according to the characteristics of the optical receiver, thereby reducing man-hours, and has the effect that the dynamic range of the optical receiver does not change even if the characteristics of the APD change over time.

[Brief description of the drawings]

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

FIG. 2 is a graph showing a relationship between a multiplication factor M and a band of a three-dimensional APD.

FIG. 3 is an NRZ equalized amplified waveform when a multiplication factor M of a three-dimensional APD is changed.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Three-way APD 2 Preamplifier circuit 3 Equalization amplifier circuit 4 High-pass filter 5 Peak detection circuit 6 Reverse bias control circuit 7 Reverse bias application circuit

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H04B 10/26 10/28 (56) References JP-A-62-154828 (JP, A) JP-A-58-124339 (JP, A) JP-A-56-152348 (JP, A) JP-A-53-59345 (JP, A) JP-A-51-58850 (JP, A) JP-A-1-321707 (JP, A) JP-A-4-107939 (JP, A) (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03F 3/08 H04B 10/06 H01L 31/10

Claims (1)

(57) [Claims] 1. A ternary APD that photoelectrically converts an optical signal to output a current signal, a preamplifier circuit that performs current-voltage conversion of the current signal and outputs a voltage signal, and equalizes and amplifies the voltage signal. an equalization amplifier for a high-pass filter for extracting only the high-frequency component of the equalized amplified signal, a peak detection circuit for detecting an amplitude peak of the high-frequency component, before
A reverse bias mark for applying a reverse bias voltage to the three-way APD
A peaking circuit detected by the peak detection circuit.
When the peak value falls below the threshold, the multiplication factor of the three-way APD
Of the reverse bias application circuit so as to increase
And a reverse bias voltage control circuit for controlling a source voltage.