Method and system for optimum channel equalization from a SerDes to an optical module

• US 8,693,885 B2
• Filed: 03/04/2010
• Issued: 04/08/2014
• Est. Priority Date: 07/22/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Ghiasi, Ali
• Primary Examiner(s): CURS, NATHAN M
• Application Number:
  US12/717,754
• Publication Number:
  US 20100221017A1
• Time in Patent Office: 1,496 Days
• Field of Search: 398/147, 398/158, 398/159
• US Class Current: 398/159
• CPC Class Codes: H04B 10/25137 using pulse shaping at the transmitter, e.g. pre-chirping or dispersion supported transmission [DST]

Abstract

Certain aspects of a method and system for optimum channel equalization between a host Serializer-Deserializer (SerDes) and an optical module may compensate and reduce dispersion loss along an electrical transmit path of a transmitter and an optical transmit path coupled to the transmitter via pre-emphasis. The data degradation as a result of the dispersion loss along the electrical transmit path of the transmitter and the optical transmit path coupled to the transmitter may be recovered by equalizing signals received via an electrical receive path of a receiver communicatively coupled to the transmitter.

Claims

1. A method for optical communication, the method comprising:

routing a signal to be transmitted along a forward electrical path of a transmitter, wherein the forward electrical path directly routes an electrical signal from the transmitter to an optical module for coupling to an optical path;

adjusting a level of pre-emphasis applied for the forward electrical path based on calculated dispersion loss along a loop electrical path, wherein the loop electrical path routes an electrical signal from the transmitter to the optical module over the forward electrical path and loops back to the transmitter over an electrical receive path from the optical module; and

applying the adjusted pre-emphasis, by a transmit feed-forward filter, to a new signal to be transmitted along the forward electrical path of the transmitter.

2. The method of claim 1, further comprising adjusting the level of pre-emphasis applied for the forward electrical path based on intersymbol interference monitored on the forward electrical path.

3. The method of claim 1, wherein the calculated dispersion loss is substantially similar to a dispersion loss along an electrical receive path of a receiver, wherein the electrical receive path of the receiver directly couples the receiver to an optical module of the receiver.

4. The method of claim 1, further comprising setting coefficients of the transmit feed-forward filter based on the calculated dispersion loss along the loop electrical path.

5. The method of claim 1, further comprising applying equalization to a received signal using a decision feedback equalizer.

6. The method of claim 1, further comprising inserting a loss into the forward electrical path to reduce an effect of multiple reflections between the transmitter and the optical module.

7. The method of claim 1, further comprising utilizing passive attenuation to reduce an effect of multiple reflections between the transmitter and the optical module.

8. A system for optical communication, the system comprising:

one or more circuits that are operable to route a signal to be transmitted along a forward electrical path of a transmitter, wherein the forward electrical path directly routes an electrical signal from the transmitter to an optical module for coupling to an optical path;

said one or more circuits further operable to adjust a level of pre-emphasis applied for the forward electrical path based on calculated dispersion loss along a loop electrical path, wherein the loop electrical path routes an electrical signal from the transmitter to the optical module over the forward electrical path and loops back to the transmitter over an electrical receive path from the optical module; and

said one or more circuits further operable to apply the adjusted pre-emphasis, by a transmit feed-forward filter, to a new signal to be transmitted along the forward electrical path of the transmitter.

9. The system of claim 8, wherein said one or more circuits are further operable to adjust the level of pre-emphasis applied for the forward electrical path based on intersymbol interference monitored on the forward electrical path.

10. The system of claim 8, wherein the calculated dispersion loss is substantially similar to a dispersion loss along an electrical receive path of a receiver, wherein the electrical receive path of the receiver directly couples the receiver to an optical module of the receiver.

11. The system of claim 8, wherein said one or more circuits are further operable to set coefficients of a transmit feed-forward filter based on the calculated dispersion loss along the loop electrical path.

12. The system of claim 8, wherein said one or more circuits are further operable to apply equalization to a received signal using a decision feedback equalizer.

13. The system of claim 8, wherein said one or more circuits are further operable to insert a loss into the forward electrical path to reduce an effect of multiple reflections between the transmitter and the optical module.

14. The system of claim 8, wherein said one or more circuits are further operable to utilize passive attenuation to reduce an effect of multiple reflections between the transmitter and the optical module.

15. A non-transitory computer readable medium having a computer program with executable instructions, when executed by a processor, cause the processor to:

direct a signal to be transmitted along a forward electrical path of a transmitter, wherein the forward electrical path directly routes an electrical signal from the transmitter to an optical module for coupling to an optical path;

adjust a level of pre-emphasis applied for the forward electrical path based on calculated dispersion loss along a loop electrical path, wherein the loop electrical path routes an electrical signal from the transmitter to the optical module over the forward electrical path and loops back to the transmitter over an electrical receive path from the optical module; and

apply the adjusted pre-emphasis to a new signal to be transmitted along the forward electrical path of the transmitter.

16. The non-transitory computer readable medium of claim 15, further causing the processor to adjust the level of pre-emphasis applied for the forward electrical path based on intersymbol interference monitored on the forward electrical path.

17. The non-transitory computer readable medium of claim 15, wherein the calculated dispersion loss is substantially similar to a dispersion loss along an electrical receive path of a receiver, wherein the electrical receive path of the receiver directly couples the receiver to an optical module of the receiver.

18. The non-transitory computer readable medium of claim 15, further causing the processor to set coefficients of a transmit feed-forward filter based on the calculated dispersion loss along the loop electrical path.

19. The non-transitory computer readable medium of claim 15, further causing the processor to insert a loss into the forward electrical path to reduce an effect of multiple reflections between the transmitter and the optical module.

20. The non-transitory computer readable medium of claim 15, further causing the processor to utilize passive attenuation to reduce an effect of multiple reflections between the transmitter and the optical module.