Optical reception circuit

Patent metadata

Field	Value
Publication number	US-2016352433-A1
Application number	US-201515114786-A
Country	US
Kind code	A1
Filing date	Feb 23, 2015
Priority date	Mar 3, 2014
Publication date	Dec 1, 2016
Grant date	—

Abstract

An optical reception circuit includes a first photodetector, a first transimpedance amplifier, a level shift circuit, a second photodetector, a second transimpedance amplifier, a peak hold circuit, and a comparator. The first transimpedance amplifier converts a first light current from the first photodetector to a first voltage. The level shift circuit generates a signal voltage from the first voltage. The second transimpedance amplifier converts the second light current from the second photodetector to a second voltage. The peak hold circuit holds a peak voltage of the second voltage as a first threshold voltage. The comparator compares the signal voltage with the first threshold voltage.

First claim

1 . An optical reception circuit comprising:
a first photodetector that receives a light signal and converts the light signal to a first light current; a first transimpedance amplifier that is connected to the first photodetector and converts the first light current to a first voltage; a level shift circuit that is connected to the first transimpedance amplifier and generates a signal voltage that is the first voltage shifted to a low-voltage side; a second photodetector that receives the light signal and converts the light signal to a second light current; a second transimpedance amplifier that is connected to the second photodetector and converts the second light current to a second voltage that is higher than a minimum voltage of the signal voltage and lower than a maximum voltage of the signal voltage; a peak hold circuit that is connected to the second transimpedance amplifier and holds a peak voltage of the second voltage as a first threshold voltage; and a comparator that is connected to the level shift circuit and the peak hold circuit and compares the signal voltage with the first threshold voltage.

2 . The optical reception circuit of claim 1 , wherein the second light current is less than the first light current.

3 . The optical reception circuit of claim 2 , wherein a light receiving area of the second photodetector is smaller than a light receiving area of the first photodetector.

4 . The optical reception circuit of claim 2 , wherein the second photodetector includes a light blocking part, the light blocking part formed so that an amount of light received by the second photodetector is smaller than an amount of light received by the first photodetector.

5 . The optical reception circuit of claim 2 , wherein a photoelectric conversion efficiency of the second photodetector is lower than a photoelectric conversion efficiency of the first photodetector.

6 . The optical reception circuit of claim 1 ,
wherein the first transimpedance amplifier includes a first amplifier and a first resistance connected in parallel with the first amplifier, wherein the second transimpedance amplifier includes a second amplifier and a second resistance connected in parallel with the second amplifier, and wherein a resistance value of the second resistance is smaller than a resistance value of the first resistance.

7 . The optical reception circuit of claim 1 , wherein the first photodetector includes a plurality of photodiodes connected in parallel with one another.

8 . The optical reception circuit of claim 1 , wherein a conversion efficiency with which the second transimpedance amplifier converts the second light current to the second voltage is lower than a conversion efficiency with which the first transimpedance amplifier converts the first light current to the first voltage.

9 . The optical reception circuit of claim 1 , wherein a displacement range of the second voltage is ½ a displacement range of the first voltage.

10 . An optical reception circuit comprising:
a first photodetector that receives a light signal and converts the light signal to a first light current; a first transimpedance amplifier that is connected to the first photodetector and converts the first light current to a first voltage; a second photodetector that receives the light signal and converts the light signal to a second light current; a second transimpedance amplifier that is connected to the second photodetector and converts the second light current to a second voltage that is higher than a minimum voltage of the first voltage and lower than a maximum voltage of the first voltage; a hold circuit that is connected to the second transimpedance amplifier and holds a peak voltage of the second voltage shifted to a high voltage side as a second threshold voltage; and a comparator that is connected to the first transimpedance amplifier and the hold circuit and compares the first voltage with the second threshold voltage.

11 . The optical reception circuit of claim 10 , wherein the hold circuit includes a level shift circuit and a peak hold circuit.

12 . The optical reception circuit of claim 10 , wherein the second light current is less than the first light current.

13 . The optical reception circuit of claim 12 , wherein a light receiving area of the second photodetector is smaller than a light receiving area of the first photodetector.

14 . The optical reception circuit of claim 12 , wherein the second photodetector includes a light blocking part, the light blocking part formed so that an amount of light received by the second photodetector is smaller than an amount of light received by the first photodetector.

15 . The optical reception circuit of claim 12 , wherein a photoelectric conversion efficiency of the second photodetector is lower than a photoelectric conversion efficiency of the first photodetector.

16 . The optical reception circuit of claim 10 ,
wherein the first transimpedance amplifier includes a first amplifier and a first resistance connected in parallel with the first amplifier, wherein the second transimpedance amplifier includes a second amplifier and a second resistance connected in parallel with the second amplifier, and wherein a resistance value of the second resistance is smaller than a resistance value of the first resistance.

17 . The optical reception circuit of claim 10 , wherein the first photodetector includes a plurality of photodiodes connected in parallel with one another.

18 . The optical reception circuit of claim 10 , wherein a conversion efficiency with which the second transimpedance amplifier converts the second light current to the second voltage is lower than a conversion efficiency with which the first transimpedance amplifier converts the first light current to the first voltage.

19 . The optical reception circuit of claim 10 , wherein a displacement range of the second voltage is ½ a displacement range of the first voltage.

Assignees

• Panasonic Ip Man Co Ltd
• Panasonic Ip Man Co Ltd

Inventors

• Nishikawa Hideo
• Niimura Yuichi
• Nakasuji Takeshi

Classifications

• H04B10/69 Primary

  Electrical arrangements in the receiver · CPC title

• H04B10/697

  Arrangements for reducing noise and distortion · CPC title

• H04B10/66

  Non-coherent receivers, e.g. using direct detection · CPC title

• H04B10/695 Primary

  Arrangements for optimizing the decision element in the receiver, e.g. by using automatic threshold control · CPC title

• H03K5/08

  by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding (H03K5/07 takes precedence; comparing one pulse with another H03K5/22; providing a determined threshold for switching H03K17/30) · CPC title