Transmitter optical signal to noise ratio improvement through receiver amplification in single laser coherent systems

Patent metadata

Field	Value
Publication number	US-10666360-B2
Application number	US-201916585700-A
Country	US
Kind code	B2
Filing date	Sep 27, 2019
Priority date	Jul 9, 2015
Publication date	May 26, 2020
Grant date	May 26, 2020

Abstract

A transceiver having an improved transmitter optical signal to noise ratio, and methods of making and using the same.

First claim

What is claimed is:

1. An optical transceiver for receiving an electrical input signal and outputting an optical output signal responsive to the electrical input signal, and for receiving an optical input signal and outputting an electrical output signal responsive to the optical input signal, comprising:
a first shared optical source configured to provide pump light;
a first splitter configured to split the pump light into a first transmitter pump light portion and a second receiver pump light portion, the first splitter configured to split the pump light into desired proportions based on the first transmitter pump light portion required for amplification of the optical output signal;
a first optical amplifier configured to receive the first transmitter pump light portion and amplify the optical output signal;
a second optical amplifier configured to receiver the second receiver pump light portion and amplify the optical input signal;
a second shared optical source configured to generate input light;
a second variable splitter configured to split the input light into signal light and local oscillator (LO) light, the second variable splitter configurable to provide a splitting ratio based on the LO light required for amplification of the optical input signal, and the second receiver pump light provided by the first splitter; and
an optical transmitter configured to receive the signal light and the electrical input signal and to transmit the optical output signal;
a coherent optical receiver configured to receive the input optical signal and the local oscillator (LO) light and to output the electrical output signal;
wherein the splitting ratio is configurable based on the desired proportions of the first splitter to trade off receiver dynamic range and transmitter optical signal to noise ratio.

2. The transceiver according to claim 1 , wherein the second optical amplifier comprises a free-running optical amplifier configured to amplify the optical input signal;
wherein the first optical amplifier comprises a gain-controlled optical amplifier configured to amplify the optical output signal; and
further comprising a first control loop configured to sample the optical output signal and to increase or decrease power to the pump light, thereby increasing or decreasing power to the first transmitter pump light portion for the first optical amplifier to increase or decrease the amplification of the optical output signal, resulting in a corresponding increase or decrease in power to the second receiver pump light portion for the second optical amplifier to increase or decrease the amplification of the optical input signal.

3. The transceiver according to claim 2 , wherein the first control loop includes a photodetector for sampling the optical output signal, and a feedback loop controller.

4. The transceiver according to claim 2 , further comprising a variable optical attenuator (VOA) configured to attenuate the optical input signal in response to amplification of the optical input signal by the second optical amplifier resulting from an increase in power to the pump light for amplification of the optical output signal by the first optical amplifier.

5. The transceiver according to claim 4 , further comprising a second control loop configured to sample a portion of an output from the coherent optical receiver, and provide a control signal to the variable optical attenuator for controlling optical power of the optical input signal received by the coherent optical receiver based on amplification by the second optical amplifier, and an optical power of the LO light.

6. The transceiver according to claim 1 , wherein the second shared optical source comprises a wavelength-tunable laser, and the first shared optical source comprises a pump laser.

7. The transceiver according to claim 1 , wherein at least one of the first optical amplifier and the second optical amplifier comprises a fiber amplifier.

8. The transceiver according to claim 1 , wherein the first splitter is configured to split the pump light, whereby the second transmitter pump light portion is smaller than the first receiver pump light portion.

9. The transceiver according to claim 8 , wherein the first splitter is configured to split the pump light by a 1:4 ratio, whereby the first transmitter pump light portion comprises four times as much pump power as the second receiver pump light portion.

10. The transceiver according to claim 1 , further comprising a first optical coupler configured to couple the first transmitter pump light portion into the first optical amplifier; and a second optical coupler configured to couple the second receiver pump light portion into the second optical amplifier.

11. The transceiver according to claim 4 , wherein the first control loop is configured to vary current to the first shared optical source in dependence upon power of the output optical signal.

12. The transceiver according to claim 11 , wherein the second variable splitter is configured to lower power of the LO light when gain in the second optical amplifier increases.

13. A method of operating an optical transceiver comprising an optical transmitter for transmitting an output optical signal, and a coherent optical receiver for receiving an input optical signal and generating an output electrical signal, the method comprising:
generating input light with a first shared optical source;
generating pump light with a second shared optical source;
splitting the pump light generated by the second shared optical source with a first splitter into first and second portions, and providing the first portion to a first optical amplifier based on required amplification of the optical output signal, and a smaller second portion to a second optical amplifier to amplify the input optical signal, thereby improving output optical signal to noise ratio (OSNR) for the optical transmitter by providing a greater portion of the pump light from the second shared optical source to the first optical amplifier in the optical transmitter; and
splitting the input light from the first shared optical source into an optical signal light and local oscillator (LO) light with a second variable splitter, and providing the optical signal light to the optical transmitter and the LO light to the coherent optical receiver, with a splitting ratio based on the LO light required for amplification of the input optical signal, and the second portion provided by the first splitter;
controlling the splitting ratio of the second variable splitter to provide a desired receiver dynamic range and transmitter OSNR.

14. The method according to claim 13 , wherein the first optical amplifier comprises a gain-controlled optical amplifier configured to amplify the output optical signal;
wherein the second optical amplifier comprises a free-running optical amplifier configured to amplify the input optical signal; and
further comprising controlling amplification of the first optical amplifier with a first control loop based on sampling the output optical signal.

15. The method according to claim 14 , further comprising attenuating the input optical signal received by the coherent optical receiver using a variable optical attenuator in a second control loop in dependence on amplification of the second optical amplifier, an optical power of the LO light, and the output electrical signal.

16. The method according to claim 14 , wherein the controlling amplification of the first optical amplifier comprises varying pump power generated by the second shared optical source in dependence upon a sample of the outpu

Assignees

• Elenion Tech Llc

Inventors

• Saathoff Guido
• Streshinsky Matthew Akio
• Palmer Robert
• Wuth Torsten

Classifications

• H04B10/40 Primary

  Transceivers · CPC title

• H04B10/615

  Arrangements affecting the optical part of the receiver · CPC title

• H05K999/99

  Electricity · mapped topic