Digital noise loading for optical receivers

Patent metadata

Field	Value
Publication number	US-9225430-B2
Application number	US-201313897872-A
Country	US
Kind code	B2
Filing date	May 20, 2013
Priority date	May 20, 2013
Publication date	Dec 29, 2015
Grant date	Dec 29, 2015

Abstract

Managing performance of an optical communications network may be facilitated by digital noise loading techniques. The digital noise loading techniques may include measuring a quality of a communication signal received at a coherent optical receiver, applying digital noise to the communication signal at the coherent optical receiver, and detecting a change in the quality of the communication signal at the coherent optical receiver in response to the application of the digital noise. Based on the change in the quality of the communication signal, an operating characteristic and/or a performance margin of the coherent optical receiver may be determined, prompting or facilitating further actions such as adjusting one or more operating parameters of the optical communications network and/or triggering an alert.

First claim

The invention claimed is:

1. An apparatus for managing performance of an optical communications network, the apparatus comprising:
logic configured to measure a quality of a communication signal received at a coherent optical receiver in the optical communications network;
logic configured to apply digital noise to the communication signal at the coherent optical receiver, wherein the digital noise is directly applied in a digital data path of the communication signal;
logic configured to detect a change in the quality of the communication signal at the coherent optical receiver in response to the application of the digital noise; and
logic configured to determine an operating characteristic and/or a performance margin of the coherent optical receiver based on the change in the quality of the communication signal.

2. The apparatus of claim 1 , wherein the applied digital noise is substantially white Gaussian noise.

3. The apparatus of claim 1 , wherein the logic configured to apply the digital noise to the communication signal is configured to apply the digital noise as a filter at a digital signal processor of the coherent optical receiver.

4. The apparatus of claim 1 , wherein the quality of the communication signal corresponds to a quality factor or a signal-to-noise ratio.

5. The apparatus of claim 1 , wherein the operating characteristic comprises values for two performance measures at a given operating point of the coherent optical receiver.

6. The apparatus of claim 5 , further comprising logic configured to determine a relationship between the two performance measures based on the change in the quality of the communication signal and a level of the digital noise applied.

7. The apparatus of claim 1 , wherein the performance margin is a quality factor margin or a signal-to-noise ratio margin representing the difference between a current operating condition and a failure condition for processing the communication signal.

8. The apparatus of claim 1 , wherein the logic configured to determine the operating characteristic and/or the performance margin comprises:
logic configured to determine a first performance margin for a first performance measure of the coherent optical receiver; and
logic configured to convert the first performance margin into a second performance margin for a second performance measure of the coherent optical receiver based on a known relationship between the first and second performance measures.

9. The apparatus of claim 1 , wherein the logic configured to apply the digital noise is configured to apply the digital noise up to a failure condition for processing the communication signal, the performance margin being determined based on a magnitude of the change upon meeting the failure condition.

10. The apparatus of claim 1 , further comprising logic configured to adjust one or more operating parameters of the optical communications network and/or to trigger an alert based on the determined performance margin and/or operating characteristic.

11. A method of managing performance of an optical communications network, the method comprising:
measuring a quality of a communication signal received at a coherent optical receiver in the optical communications network;
applying digital noise to the communication signal at the coherent optical receiver, wherein the digital noise is directly applied in a digital data path of the communication signal;
detecting a change in the quality of the communication signal at the coherent optical receiver in response to the application of the digital noise; and
determining an operating characteristic and/or a performance margin of the coherent optical receiver based on the change in the quality of the communication signal.

12. The method of claim 11 , wherein the applied digital noise is substantially white Gaussian noise.

13. The method of claim 11 , wherein the digital noise is applied to the communication signal via a filter at a digital signal processor of the coherent optical receiver.

14. The method of claim 11 , wherein the quality of the communication signal corresponds to a quality factor or a signal-to-noise ratio.

15. The method of claim 11 , wherein the operating characteristic comprises values for two performance measures at a given operating point of the coherent optical receiver.

16. The method of claim 15 , further comprising determining a relationship between the two performance measures based on the change in the quality of the communication signal and a level of the digital noise applied.

17. The method of claim 11 , wherein the performance margin is a quality factor margin or a signal-to-noise ratio margin representing the difference between a current operating condition and a failure condition for processing the communication signal.

18. The method of claim 11 , wherein determining the operating characteristic and/or the performance margin comprises:
determining a first performance margin for a first performance measure of the coherent optical receiver; and
converting the first performance margin into a second performance margin for a second performance measure of the coherent optical receiver based on a known relationship between the first and second performance measures.

19. The method of claim 11 , wherein the digital noise is applied up to a failure condition for processing the communication signal, the performance margin being determined based on a magnitude of the change upon meeting the failure condition.

20. A coherent optical receiver, comprising:
an optical front end coupled to Analog-to-Digital Converters (ADCs);
a Digital Signal Processor (DSP) coupled to the ADCs;
Forward Error Correction (FEC) circuitry coupled to the DSP; and
a performance characterizer coupled to the DSP and the FEC circuitry, wherein the performance characterizer is configured to
apply digital noise to a digital communication signal created by the ADCs in response to an optical signal from the optical front end, wherein the digital noise is directly applied in a digital data path of the communication signal,
detect a change in the quality of the digital communication signal based on measurements by the FEC circuitry in response to the application of the digital noise, and
determine an operating characteristic and/or a performance margin of the coherent optical receiver based on the change in the quality of the digital communication signal.

Assignees

• Ciena Corp

Inventors

• Harley James
• Gaudette Jamie
• Jakober Lukas
• Hartling Elizabeth Rivera
• Riaz Bilal

Classifications

• H04B10/616 Primary

  Details of the electronic signal processing in coherent optical receivers · CPC title

• H04B10/0799

  Monitoring line transmitter or line receiver equipment · CPC title

• H04B10/07953 Primary

  Monitoring or measuring OSNR, BER or Q · CPC title