Optical receiving circuit, optical transceiver, and control method for optical receiving circuit

Patent metadata

Field	Value
Publication number	US-9800351-B2
Application number	US-201615273073-A
Country	US
Kind code	B2
Filing date	Sep 22, 2016
Priority date	Oct 7, 2015
Publication date	Oct 24, 2017
Grant date	Oct 24, 2017

Abstract

An apparatus includes a photodiode configured to detect an optical signal; a common-base amplifier configured to input a current signal converted from the optical signal by the photodiode; an common-emitter amplifier configured to couple to an output of the common-base amplifier; a first circuit configured to feed back the output of the common-emitter amplifier to an output of the common-base amplifier; and a second circuit configured to, when power of the optical signal exceeds a predetermined level, reduce a load resistance value of the common-base amplifier and increase an emitter current of the common-emitter amplifier.

First claim

What is claimed is:

1. An apparatus, comprising:
a photodiode configured to detect an optical signal;
a common-base amplifier configured to input a current signal converted from the optical signal by the photodiode;
a common-emitter amplifier configured to couple to an output of the common-base amplifier;
a first circuit configured to feed back the output of the common-emitter amplifier to an output of the common-base amplifier; and
a second circuit configured to, when power of the optical signal exceeds a predetermined level, reduce a load resistance value of the common-base amplifier and increase an emitter current of the common-emitter amplifier.

2. The apparatus according to claim 1 , wherein
the second circuit is configured to, when the power of the optical signal exceeds the predetermined level, reduce the load resistance value of the common-base amplifier by a first switch and increase the emitter current of the common-emitter amplifier by a second switch.

3. An apparatus, comprising an optical receiver including:
a photodiode configured to detect an optical signal;
a common-base amplifier configured to input a current signal from the photodiode;
a common-emitter amplifier configured to couple to an output of the common-base amplifier;
a feedback circuit configured to feed back the output of the common-emitter amplifier to an output of the common-base amplifier; and
a switching circuit configured to switch, based on power of the optical signal, magnitude of load resistance of the common-base amplifier and magnitude of an emitter current of the common-emitter amplifier.

4. The apparatus according to claim 3 , wherein
when the power of the optical signal exceeds a predetermined level, the switching circuit reduces the load resistance of the common-base amplifier and increases the emitter current of the common-emitter amplifier.

5. The apparatus according to claim 3 , wherein
the common-base amplifier includes a current source, and
when the power of the optical signal is equal to or lower than the predetermined level, the switching circuit increases the load resistance of the common-base amplifier and reduces an electric current of the current source.

6. The apparatus according to claim 5 , wherein, when the power of the optical signal exceeds the predetermined level, the switching circuit reduces the load resistance and increases the electric current of the current source.

7. The apparatus according to claim 3 , wherein
the common-base amplifier includes a first load and a second load connected to a power supply voltage in parallel and a first switching transistor connected to one of the first load and the second load in series,
the common-emitter amplifier includes a first current source and a second current source which are connected in parallel to reference potential, and a second switching transistor connected in series to one of the first current source and the second current source, and
the switching circuit controls ON/OFF of the first switching transistor and the second switching transistor based on the power of the optical signal.

8. The apparatus according to claim 7 , wherein
the switching circuit includes an optical-power detection circuit configured to monitor the power of the optical signal, and a switching-signal generation circuit configured to generate a switch signal based on an output of the optical-power detection circuit, and
the switch signal is connected to the first switching transistor and the second switching transistor.

9. The apparatus according to claim 3 , wherein
the current source of the common-base amplifier includes a third load and a fourth load which are connected in parallel to reference potential, and a third switching transistor connected in series to one of the third load and the fourth load, and
the switching circuit controls ON/OFF of the third switching transistor.

10. The apparatus according to claim 3 , wherein
the switching circuit includes an optical-power detection circuit configured to monitor the power of the optical signal, and a switch-signal generation circuit configured to generate a switch signal based on an output of the optical-power detection circuit, and
the switch-signal generation circuit generates a digital switch signal, a switch signal with hysteresis adjusted, or an analog switch signal.

11. The apparatus according to claim 10 , wherein the optical-power detection circuit is coupled to the output of the common-emitter amplifier and monitors the power of the optical signal.

12. The apparatus according to claim 10 , wherein the optical-power detection circuit is connected to a cathode of the photodiode and monitors the power of the optical signal.

13. The apparatus according to claim 3 , further comprising:
an optical transceiver; wherein
the optical transceiver comprises the optical receiver and an optical transmitter.

14. A control method for an optical receiving circuit, comprising:
detecting power of an optical signal received by an optical receiving circuit;
when the power of the optical signal exceeds a predetermined level, reducing, by a first signal output from a circuit, load resistance of a common-base amplifier of the optical receiving circuit and increasing, by a second signal output from the circuit, an emitter current of a common-emitter amplifier connected to an output of the common-base amplifier; and
feeding back an output of the common-emitter amplifier to the output of the common-base amplifier.

15. The control method for the optical receiving circuit according to claim 14 , wherein
a current source is disposed on a reference voltage side of the common-base amplifier, and
the control method further comprises, when the power of the optical signal is equal to or lower than the predetermined level, increasing the load resistance of the common-base amplifier and reducing an electric current of the current source.

16. The control method for the optical receiving circuit according to claim 15 , further comprising, when the power of the optical signal exceeds the predetermined level, reducing the load resistance and increasing the electric current of the current source.

Assignees

• Fujitsu Ltd

Inventors

• Shiraishi Takashi

Classifications

• H04B10/691 Primary

  Arrangements for optimizing the photodetector in the receiver · CPC title

• H03F3/08

  controlled by light · CPC title

• H03F3/45089 Primary

  Non-folded cascode stages · CPC title

• H04B10/693

  Arrangements for optimizing the preamplifier in the receiver · CPC title

• H03F2203/45722

  the LC comprising one or more source followers, as post buffer or driver stages, in cascade in the LC · CPC title