Preamplifier, optical receiver, optical termination device, and optical communication system

Patent metadata

Field	Value
Publication number	US-9450542-B2
Application number	US-201314413483-A
Country	US
Kind code	B2
Filing date	Jan 16, 2013
Priority date	Jan 16, 2013
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

A current bypass circuit that passes part of a photocurrent output from a photodetector is connected to an input terminal of a current-to-voltage conversion amplifier circuit. A voltage obtained by level conversion of an output voltage by a voltage level conversion circuit is input into the current bypass circuit so that the current bypass circuit is turned on at a photocurrent that is smaller than the photocurrent at which a diode connected in parallel to a feedback resistor of the current-to-voltage conversion amplifier circuit is turned on. Consequently, the current-to-voltage conversion gain is switched in three stages according to the intensity of the photocurrent corresponding to an optical signal level.

First claim

The invention claimed is:

1. A preamplifier comprising:
a current-to-voltage conversion amplifier circuit that converts all or part of a signal current into a signal voltage, and amplifies and outputs the signal voltage;
a gain varying portion that varies a conversion gain of the current-to-voltage conversion amplifier circuit so that the conversion gain has a point of variation when an input current is equal to a first threshold value;
a current bypass circuit that bypasses part of the signal current according to the intensity of the signal current; and
a voltage level conversion circuit that outputs to the current bypass circuit a level-converted voltage obtained by level conversion of the signal voltage at a predetermined ratio;
wherein a second threshold value that is the intensity of the input current of the current-to-voltage conversion amplifier circuit when the level-converted voltage output from the voltage level conversion circuit becomes a voltage of a threshold value for switching between whether or not to execute a bypass of the current bypass circuit, is less than the first threshold value.

2. The preamplifier according to claim 1 , wherein
the signal current is a photocurrent generated by photoelectric conversion of received light by a photodetector, and corresponds to the intensity of the received light, and
the current-to-voltage conversion amplifier circuit outputs the signal voltage as a received signal.

3. The preamplifier according to claim 1 , wherein
the current-to-voltage conversion amplifier circuit includes a feedback resistor between an input/output of an amplifier,
the gain varying portion includes a first diode connected in parallel to the feedback resistor between the input/output of the amplifier, and
the first threshold value is the input current of the current-to-voltage conversion amplifier circuit when the value of the voltage at both ends of the first diode is a threshold voltage of the first diode.

4. The preamplifier according to claim 1 , wherein
the current bypass circuit includes a PNP bipolar transistor that has an emitter connected to an input of the current-to-voltage conversion amplifier circuit, and
the level-converted voltage input into the current bypass circuit from the voltage level conversion circuit is input into a base of the PNP bipolar transistor.

5. The preamplifier according to claim 4 , wherein
the current bypass circuit further includes an N channel field effect transistor including a gate biased to a predetermined potential, or an NPN bipolar transistor including a base biased to a predetermined potential, and
a source of the N channel field effect transistor or an emitter of the NPN bipolar transistor is connected to the emitter of the PNP bipolar transistor.

6. The preamplifier according to claim 3 , wherein
the current bypass circuit includes a second diode, and
the level-converted voltage input into the current bypass circuit from the voltage level conversion circuit is input into a cathode of the second diode.

7. The preamplifier according to claim 1 , wherein
the voltage level conversion circuit is connected in series to a plurality of resistors, and outputs a voltage divided by the plurality of resistors as the level-converted voltage.

8. The preamplifier according to claim 1 , wherein
the voltage level conversion circuit includes a configuration with an NPN bipolar transistor or an N channel field effect transistor connected in series to a current source, and outputs a voltage at an input terminal of the current source as the level-converted voltage.

9. The preamplifier according to claim 1 , wherein
the current bypass circuit includes a configuration with a plurality of current bypass modules of the same configuration connected in parallel to each other,
the voltage level conversion circuit respectively outputs to the plurality of the current bypass modules a plurality of the level-converted voltage obtained by level conversion at different ratios, and
each of the current bypass modules switches between whether or not to execute a bypass of the current bypass module based on the level-converted voltage.

10. An optical receiver comprising a photodetector that photoelectrically converts received light and outputs a photocurrent corresponding to the intensity of the received light, and a preamplifier that outputs a received signal based on the photocurrent, wherein
the preamplifier includes
a current-to-voltage conversion amplifier circuit that converts all or part of a signal current into a signal voltage, and amplifies and outputs the signal voltage,
a gain varying portion that varies a conversion gain of the current-to-voltage conversion amplifier circuit so that a intensity of an input current of the current-to-voltage conversion amplifier circuit being a first threshold value is treated as a point of variation,
a current bypass circuit that bypasses part of the signal current according to the intensity of the signal current, and
a voltage level conversion circuit that outputs to the current bypass circuit a level-converted voltage obtained by level conversion of the signal voltage at a predetermined ratio, wherein

a second threshold value that is the intensity of the input current of the current-to-voltage conversion amplifier circuit when the level-converted voltage output from the voltage level conversion circuit becomes a voltage of a threshold value for switching between whether or not to execute a bypass of the current bypass circuit, is less than the first threshold value.

11. An optical line terminating apparatus comprising the optical receiver of claim 10 .

12. An optical communication system comprising the optical line terminating apparatus of claim 11 .

Assignees

• Mita Daisuke
• Noda Masaki
• Nogami Masamichi
• Mitsubishi Electric Corp

Inventors

• Mita Daisuke
• Noda Masaki
• Nogami Masamichi

Classifications

• H03G3/3084

  in receivers or transmitters for electromagnetic waves other than radiowaves, e.g. lightwaves (H03G3/32, H03G3/34 take precedence) · CPC title

• H03F3/08 Primary

  controlled by light · CPC title