Deliberate signal degradation for optimizing receiver control loops

• US 20070053688A1
• Filed: 09/07/2005
• Published: 03/08/2007
• Est. Priority Date: 09/07/2005
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Gronbach, Siegfried, Benz, Andreas, Seitz, Roland
• Granted Patent: US 7,609,981 B2
• Time in Patent Office: Days
• US Class Current: 398/27
• CPC Class Codes: H04B 10/077 using a supervisory or additional signal
• CPC Class Codes: H04B 10/07953 Monitoring or measuring OSNR, BER or Q
• CPC Class Codes: H04B 10/07955 Monitoring or measuring power
• CPC Class Codes: H04B 10/2513 due to chromatic dispersion
• CPC Class Codes: H04B 10/2572 due to forms of polarisation-dependent distortion other than PMD
• CPC Class Codes: H04B 10/66 Non-coherent receivers, e.g. using direct detection

Abstract

Techniques to control an optical receiver having a control loop using Bit Error Rate (BER). In one implementation, a bit error rate (BER) associated with a received optical signal is determined. Indication of the BER to a control loop adapted is provided to adjust the optical signal in a manner tending to reduce the BER. The received optical signal is adapted in a manner tending to increase the BER such that the control loop operates within an active control region.

Claims

1. A method, comprising:

determining a bit error rate (BER) associated with a received optical signal;

providing indication of said BER to a control loop adapted to adjust the optical signal in a manner tending to reduce the BER, and

adapting the received optical signal in a manner tending to increase the BER such that the control loop operates within an active control region.

2. The method of claim 1, wherein the manner includes adjusting at least one control parameter.

3. The method of claim 2, wherein the adjusted control parameter is a decision threshold.

4. The method of claim 3, wherein the optimum decision threshold is determined using dithering.

5. The method of claim 3, wherein the decision threshold is adjusted by shifting the decision threshold from a positive number of arbitrary units to a negative number of arbitrary units and back to the positive number of arbitrary units.

6. The method of claim 2, wherein the control parameter comprises feedback control for adapting sampling phase, chromatic dispersion, polarization mode dispersion, or input/output power of the received optical signal.

7. The method of claim 2, wherein the manner includes one or more of loading the signal with optical noise and loading the signal with electrical noise.

8. The method of claim 1, wherein the adapting step further includes transmission of a vertical eye opening value as a feedback control signal.

9. The method of claim 8, wherein the vertical eye opening and BER are determined using a common processing element.

10. A method adapted for use in an optical receiver normally providing an indication of a bit error rate (BER) associated with a received optical signal, the BER indication adapted for use by a control loop, the control loop having associated with it an active control region, the method comprising:

adapting at least one parameter of the received optical signal to increase the BER such that the control loop operates within the active control region.

11. The method of claim 10, wherein the adapted parameter is a decision threshold.

12. The method of claim 11, wherein the optimum decision threshold is determined using dithering.

13. The method of claim 10, wherein the at least one parameter is selected from a group consisting of:

the sampling phase, chromatic dispersion, polarization mode dispersion, input power and output power.

14. The method of claim 10, wherein the adapting step further includes transmission of a vertical eye opening value as a feedback control signal.

15. In a data transmission system wherein data transmitted to a receiver via a network is adapted via a transmitter control mechanism in response to a bit error rate (BER) signal provided by the receiver, a method comprising:

adjusting, at said receiver, at least one parameter of a received data signal to cause the BER associated with the received data signal to be within a range of BER values, said range of BER values corresponding to an active control region of the transmitter control region.

16. The method of claim 15, wherein the adjusted parameter is a decision threshold.

17. The method of claim 16, wherein the decision threshold is determined using dithering.

18. The method of claim 16, wherein the decision threshold is adjusted by shifting the decision threshold from a positive number of arbitrary units to a negative number of arbitrary units and back to the positive value of arbitrary units.

19. The method of claim 15, wherein the control parameter comprises feedback control for adjusting one or more of sampling phase, chromatic dispersion, polarization mode dispersion, and input/output power of the received optical signal.

20. The method of claim 15 further comprising transmitting a vertical eye opening value as a feedback control signal.