Methods and systems for digitally processing optical data signals

• US 7,564,866 B2
• Filed: 07/23/2001
• Issued: 07/21/2009
• Est. Priority Date: 07/21/2000
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Gopinathan, Venugopal, Agazzi, Oscar
• Primary Examiner(s): Trost, IV; William
• Assistant Examiner(s): Nguyen; Toan D
• Application Number:
  US09/909,896
• Publication Number:
  US 20020012152A1
• Time in Patent Office: 2,920 Days
• Field of Search: 370/290, 370/467, 370/497, 370/463, 370/466, 375/229, 375/232, 375/233, 375/262, 375/264, 375/265, 375/341, 375/348, 375/349, 375/144, 375/260, 375/267, 375/342, 375/355, 375/316, 375/340, 375/350, 375/347, 710/69, 398/79, 398/82, 398/140, 398/141, 398/158, 398/202, 398/208
• US Class Current: 370/463
• CPC Class Codes: H03M 1/0604 at one point, i.e. by adjusting a single reference value, e.g. bias or gain error gain setting for range control H03M1/18
• CPC Class Codes: H03M 1/0607 Offset or drift compensation removal of offset already present on the analogue input signal H03M1/1295
• CPC Class Codes: H03M 1/0624 by synchronisation
• CPC Class Codes: H03M 1/0836 of phase error, e.g. jitter
• CPC Class Codes: H03M 1/1215 using time-division multiplexing
• CPC Class Codes: H04B 10/6933 Offset control of the differential preamplifier
• CPC Class Codes: H04B 10/697 Arrangements for reducing noise and distortion
• CPC Class Codes: H04B 10/6971 using equalisation
• CPC Class Codes: H04L 2025/03445 Time domain
• CPC Class Codes: H04L 25/03057 with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 7/0062 detection of error based on data decision error, e.g. Mueller type detection

Abstract

Digital signal processing based methods and systems for receiving optical data signals include parallel receivers, multi-channel receivers, timing recovery schemes, equalization schemes, and multi-path parallel receivers in which an analog-to-digital converter (“ADC”) and/or a digital signal processor (“DSP”) are implemented with parallel paths that operate at lower rates than the received data signal.

Claims

1. A method for receiving an optical data signal, comprising:

(1) receiving an optical data signal;

(2) converting the optical data signal to an electrical signal having a symbol rate;

(3) generating N sampling signals having a first frequency that is lower than the symbol rate, the N sampling signals shifted in phase relative to one another, wherein N is an integer greater than one;

(4) controlling N analog-to-digital converter (“

ADC”

) paths with the N sampling signals to sample the electrical signal at the phases, to produce samples;

(5) performing at least one M-path parallel digital process on the samples, wherein M is greater than N; and

(6) generating a digital signal representation of the optical data signal from the samples.

2. The method according to claim 1, wherein step (5) further comprises performing an equalization process on the samples.

3. The method according to claim 2, wherein step (5) further comprises performing a Viterbi equalization process on the samples.

4. The method according to claim 2, wherein step (5) further comprises performing a feed-forward equalization process on the samples.

5. The method according to claim 2, wherein step (5) further comprises performing a decision feedback equalization process on the samples.

6. The method according to claim 2, wherein step (5) further comprises performing Viterbi equalization and feed-forward equalization processes on the samples.

7. The method according to claim 2, wherein step (5) further comprises performing Viterbi equalization and decision feedback equalization processes on the samples.

8. The method according to claim 2, wherein step (5) further comprises:

performing one or more of the following types of equalization processes on the samples;

Viterbi equalization;

feed-forward equalization; and

decision feedback equalization.

9. The method according to claim 2, wherein step (1) comprises receiving the optical data signal from a multimode optical fiber and step (5) comprises equalizing multimode dispersion from the multimode optical fiber.

10. The method according to claim 2, wherein step (1) comprises receiving the optical data signal from a single mode optical fiber and step (5) comprises equalizing chromatic and/or waveguide dispersion from the single mode optical fiber.

11. The method according to claim 2, wherein step (1) comprises receiving the optical data signal from a multimode optical fiber and step (5) comprises equalizing chromatic and/or waveguide dispersion from the multimode optical fiber.

12. The method according to claim 2, wherein step (1) comprises receiving the optical data signal from a single mode optical fiber and step (5) comprises equalizing polarization mode dispersion from the single mode optical fiber.

13. The method according to claim 2, wherein step (1) comprises receiving the optical data signal from a single mode optical fiber and step (5) comprises equalizing dispersion induced in the single mode optical fiber by laser chirping.

14. The method according to claim 2, wherein step (1) comprises receiving the optical data signal from a transmitter that lacks external modulators, and step (5) comprises equalizing excess dispersion induced by laser chirping.

15. The method according to claim 1, wherein step (5) comprises decoding a convolutional code.

16. The method according to claim 1, wherein step (5) comprises decoding a trellis code.

17. The method according to claim 1, wherein step (5) comprises decoding a block code.

18. The method according to claim 1, wherein M equals 2N.

19. An optical receiver, comprising:

a receiver input;

an optical-to-electrical converter coupled to the receiver input;

an analog-to-digital converter (“

ADC”

) array of N ADC paths, wherein N is an integer greater than 1, each ADC path including an ADC path input coupled to an output of the optical-to-electrical converter; and

an M-path digital signal processor coupled to the ADC array, wherein M is greater than N.

20. The optical receiver according to claim 19, wherein the digital signal processor includes an equalizer.

21. The optical receiver according to claim 20, wherein the equalizer comprises a Viterbi equalizer.

22. The optical receiver according to claim 20, wherein the equalizer comprises a feed-forward equalizer.

23. The optical receiver according to claim 20, wherein the equalizer comprises a decision feedback equalizer.

24. The optical receiver according to claim 20, wherein the equalizer comprises a Viterbi equalizer and a feed-forward equalizer.

25. The optical receiver according to claim 20, wherein the equalizer comprises a Viterbi equalizer and a decision feedback equalizer.

26. The optical receiver according to claim 20, wherein the equalizer comprises a feed-forward equalizer and a decision feedback equalizer.

27. The optical receiver according to claim 20 wherein the equalizer comprises one or more of:

a Viterbi equalizer;

a feed-forward equalizer; and

a decision feedback equalizer.

28. The optical receiver according to claim 20, wherein the input is coupled to a multimode optical fiber and the equalizer equalizes multimode dispersion from the multimode optical fiber.

29. The optical receiver according to claim 20, wherein the input is coupled to a single mode optical fiber and the equalizer equalizes chromatic and/or waveguide dispersion from the single mode optical fiber.

30. The optical receiver according to claim 20, wherein the input is coupled to a multimode optical fiber and the equalizer equalizes chromatic and/or waveguide dispersion in the multimode optical fiber.

31. The optical receiver according to claim 20, wherein the input is coupled to a multimode optical fiber and the equalizer equalizes polarization mode dispersion from the single mode optical fiber.

32. The optical receiver according to claim 20, wherein the input is coupled to a single mode optical fiber and the equalizer equalizes dispersion induced in the single mode optical fiber by laser chirping.

33. The optical receiver according to claim 20, wherein the input receives the optical data signal from a transmitter that lacks external modulators, and the equalizer equalizes excess dispersion induced by laser chirping.

34. The optical receiver according to claim 19, wherein the digital signal processor comprises a convolutional decoder.

35. The optical receiver according to claim 19, wherein the digital signal processor comprises a trellis decoder.

36. The optical receiver according to claim 19, wherein the digital signal processor comprises a block decoder.

37. The optical receiver according to claim 19, wherein M equals 2N.

38. An optical receiver, comprising:

means for receiving an optical data signal;

means for converting the optical data signal to an electrical signal having a symbol rate;

means for generating N sampling signals having a first frequency that is lower than the symbol rate, the N sampling signals shifted in phase relative to one another;

means for controlling N analog-to-digital converter (“

ADC”

) paths with the N sampling signals to sample the electrical signal at the phases to produce samples;

means for performing at least one M-path parallel digital process on the samples, wherein M is greater than N; and

means for generating a digital signal representation of the optical data signal from the samples.

39. The system according to claim 38, wherein the means for performing digital processes on the samples include means for equalizing the samples.

40. The system according to claim 39, wherein the means for equalizing the samples comprise means for performing a Viterbi equalization process on the samples.

41. The system according to claim 39, wherein the means for equalizing the samples comprise means for performing a feed-forward equalization process on the samples.

42. The system according to claim 39, wherein the means for equalizing the samples comprise means for performing a decision feedback equalization process on the samples.

43. The system according to claim 39, wherein the means for equalizing the samples comprise means for performing Viterbi equalization and feed-forward equalization processes on the samples.

44. The system according to claim 39, wherein the means for equalizing the samples comprises means for performing Viterbi equalization and decision feedback equalization processes on the samples.

45. The optical receiver according to claim 39, wherein the means for receiving an optical signal is coupled to a multimode optical fiber and the means for equalizing comprises means for equalizing multimode dispersion from the multimode optical fiber.

46. The optical receiver according to claim 39, wherein the means for receiving an optical signal is coupled to a single mode optical fiber and the means for equalizing comprises means for equalizing chromatic and/or waveguide dispersion from the single mode optical fiber.

47. The optical receiver according to claim 39, wherein the means for receiving an optical signal is coupled to a multimode optical fiber and the means for equalizing comprises means for equalizing chromatic and/or waveguide dispersion in the multimode optical fiber.

48. The optical receiver according to claim 39, wherein the means for receiving an optical signal is coupled to a multimode optical fiber and the means for equalizing comprises means for equalizing polarization mode dispersion from the single mode optical fiber.

49. The optical receiver according to claim 39, wherein the means for receiving an optical signal is coupled to a single mode optical fiber and the means for equalizing comprises means for equalizing dispersion induced in the single mode optical fiber by laser chirping.

50. The optical receiver according to claim 39, wherein the means for receiving an optical signal receives the optical data signal from a transmitter that lacks external modulators, and the means for equalizing comprises means for equalizing excess dispersion induced by laser chirping.

51. The optical receiver according to claim 38, wherein the means for performing digital processes on the samples comprises means for decoding a convolutional code.

52. The optical receiver according to claim 38, wherein the means for performing digital processes on the samples comprises means for decoding a trellis code.

53. The optical receiver according to claim 38, wherein the means for digitally performing digital processes on the samples comprises means for decoding a block code.

54. The system according to claim 38, wherein M equals 2N.