Methods and systems for digitally processing optical data signals

• US 20020012152A1
• Filed: 07/23/2001
• Published: 01/31/2002
• Est. Priority Date: 07/21/2000
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Gopinathan, Venugopal, Agazzi, Oscar
• Granted Patent: US 7,564,866 B2
• Time in Patent Office: Days
• US Class Current: 398/202
• 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 electrical and/or optical data signals include electrical receivers, optical receivers, parallel receivers, multi-channel receivers, timing recovery schemes, and, without limitation, equalization schemes. The present invention is implemented as a single path receiver. Alternatively, the present invention is implemented as a multi-path parallel receiver 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. In an embodiment, a parallel DSP-based receiver in accordance with the invention includes a separate timing recovery loop for each ADC path. The separate timing recovery loops can be used to compensate for timing phase errors in the clock generation circuit that are different for each path. In an embodiment, a parallel DSP-based receiver includes a separate automatic gain control (AGC) loop for each ADC path. The separate AGC loops can be used to compensate for gain errors on a path-by-path basis. In an embodiment, a parallel DSP-based receiver includes a separate offset compensation loop for each ADC path. The separate offset compensation loops can be used to independently compensate for offsets that are different for each path. In an embodiment the present invention is implemented as a multi-channel receiver that receives a plurality of data signals. In an embodiment, a receiver performs DSP-based equalization on electrical data signals and/or on electrical representations of optical data signals. Equalization is performed in single path receivers and parallel multi-path receivers, on electrical data signals and/or optical data signals. One or more of the following types of equalization are performed, alone and/or in various combinations with one another: Viterbi equalization; feed-forward equalization (“FFE”); and/or decision feed-back equalization (“DFE,”).

Claims

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

(1) receiving an optical data signal;

(2) converting the optical signal to an electrical signal;

(3) converting the electrical signal to a digital electrical signal; and

(4) digitally processing the digital electrical signal.

2. The method according to claim 1, wherein step (4) comprises the step of equalizing the digital electrical signal.

3. The method according to claim 2, wherein step (4) further comprises the step of performing Viterbi equalization on the digital electric signal.

4. The method according to claim 2, wherein step (4) further comprises the step of performing feed-forward equalization on the digital electric signal.

5. The method according to claim 2, wherein step (4) further comprises the step of performing decision feedback equalization on the digital electric signal.

6. The method according to claim 2, wherein step (4) further comprises the step of performing Viterbi equalization and feed-forward equalization on the digital electric signal.

7. The method according to claim 2, wherein step (4) further comprises the step of performing Viterbi equalization and decision feedback equalization on the digital electric signal.

8. The method according to claim 2, wherein step (4) further comprises

the step performing one or more of the following types of equalization on the digital electric signal:

Viterbi equalization;

feed-forward equalization; and

decision feedback equalization.

12. The optical receiver according to claim 8, wherein said equalizer comprises a feed-forward equalizer.

13. The optical receiver according to claim 8, wherein said equalizer comprises a decision feedback equalizer.

14. The optical receiver according to claim 8, wherein said equalizer comprises a Viterbi equalizer and a feed-forward equalizer.

15. The optical receiver according to claim 8, wherein said equalizer comprises a Viterbi equalizer and a decision feedback equalizer.

16. The optical receiver according to claim 8, wherein said equalizer comprises a feed-forward equalizer and a decision feedback equalizer.

17. The optical receiver according to claim 8, wherein said equalizer comprises one or more of:

a Viterbi equalizer;

a feed-forward equalizer; and

a decision feedback equalizer.

25. The method according to claim 1, wherein step (1) comprises the step of receiving the optical data signal from a multimode optical fiber and step (4) comprises the step of equalizing multimode dispersion from the multimode optical fiber.

26. The method according to claim 1, wherein step (1) comprises the step of receiving the optical data signal from a single mode optical fiber and step (4) comprises the step of equalizing chromatic and/or waveguide dispersion from the single mode optical fiber.

27. The method according to claim 1, wherein step (1) comprises the step of receiving the optical data signal from a multimode optical fiber and step (4) comprises the step of equalizing chromatic and/or waveguide dispersion from the multimode optical fiber.

28. The method according to claim 1, wherein step (1) comprises the step of receiving the optical data signal from a single mode optical fiber and step (4) comprises the step of equalizing polarization mode dispersion from the single mode optical fiber.

29. The method according to claim 1, wherein step (1) comprises the step of receiving the optical data signal from a single mode optical fiber and step (4) comprises the step of equalizing dispersion induced in the single mode optical fiber by laser chirping.

30. The method according to claim 1, wherein step (1) comprises the step of receiving the optical data signal from a transmitter that lacks external modulators, and step (4) comprises the step of equalizing excess dispersion induced by laser chirping.

43. The method according to claim 1, wherein step (4) comprises the step of decoding a convolutional code.

44. The method according to claim 1, wherein step (4) comprises the step of decoding a trellis code.

45. The method according to claim 1, wherein step (4) comprises the step of decoding a block code.

9. An optical receiver, comprising:

an input;

an optical-to-electrical converter coupled to said input;

an analog-to-digital converter coupled to said optical-to-electrical converter;

an digital signal processor coupled to said analog-to-digital converter.

10. The optical receiver according to claim 9, wherein said digital signal processor includes an equalizer.

11. The optical receiver according to claim 10, wherein said equalizer comprises a Viterbi equalizer.

31. The optical receiver according to claim 10, wherein said input is coupled to a multimode optical fiber and said equalizer equalizes multimode dispersion from the multimode optical fiber.

32. The optical receiver according to claim 10, wherein said input is coupled to a single mode optical fiber and said equalizer equalizes chromatic and/or waveguide dispersion from the single mode optical fiber.

33. The optical receiver according to claim 10, wherein said input is coupled to a multimode optical fiber and said equalizer equalizes chromatic and/or waveguide dispersion in the multimode optical fiber.

34. The optical receiver according to claim 10, wherein said input is coupled to a multimode optical fiber and said equalizer equalizes polarization mode dispersion from the single mode optical fiber.

35. The optical receiver according to claim 10, wherein said input is coupled to a single mode optical fiber and said equalizer equalizes dispersion induced in the single mode optical fiber by laser chirping.

36. The optical receiver according to claim 10, wherein said input receives the optical data signal from a transmitter that lacks external modulators, and said equalizer equalizes excess dispersion induced by laser chirping.

46. The optical receiver according to claim 9, wherein said digital signal processor comprises a convolutional decoder.

47. The optical receiver according to claim 9, wherein said digital signal processor comprises a trellis decoder.

48. The optical receiver according to claim 9, wherein said digital signal processor comprises a block decoder.

18. An optical receiver, comprising:

means for receiving an optical data signal;

means for converting the optical signal to an electrical signal;

means for converting the electrical signal to a digital electrical signal; and

means for digitally processing the digital electrical signal.

19. The system according to claim 18, wherein said means for digitally processing the digital electrical signal include means for equalizing the digital electrical signal.

20. The system according to claim 19, wherein said means for equalizing the digital electrical signal comprise means for performing Viterbi equalization on the digital electrical signal.

21. The system according to claim 19, wherein said means for equalizing the digital electrical signal comprise means for performing feed-forward equalization on the digital electrical signal.

22. The system according to claim 19, wherein said means for equalizing the digital electrical signal comprise means for performing decision feedback equalization on the digital electrical signal.

23. The system according to claim 19, wherein said means for equalizing the digital electrical signal comprise means for performing Viterbi equalization and feed-forward equalization on the digital electrical signal.

24. The system according to claim 19, wherein said means for equalizing the digital electrical signal comprises means for performing Viterbi equalization and decision feedback equalization on the digital electrical signal.

37. The optical receiver according to claim 19, wherein said means for receiving an optical signal is coupled to a multimode optical fiber and said means for equalizing comprises means for equalizing multimode dispersion from the multimode optical fiber.

38. The optical receiver according to claim 19, wherein said means for receiving an optical signal is coupled to a single mode optical fiber and said means for equalizing comprises means for equalizing chromatic and/or waveguide dispersion from the single mode optical fiber.

39. The optical receiver according to claim 19, wherein said means for receiving an optical signal is coupled to a multimode optical fiber and said means for equalizing comprises means for equalizing chromatic and/or waveguide dispersion in the multimode optical fiber.

40. The optical receiver according to claim 19, wherein said means for receiving an optical signal is coupled to a multimode optical fiber and said means for equalizing comprises means for equalizing polarization mode dispersion from the single mode optical fiber.

41. The optical receiver according to claim 19, wherein said means for receiving an optical signal is coupled to a single mode optical fiber and said means for equalizing comprises means for equalizing dispersion induced in the single mode optical fiber by laser chirping.

42. The optical receiver according to claim 19, wherein said means for receiving an optical signal receives the optical data signal from a transmitter that lacks external modulators, and said means for equalizing comprises means for equalizing excess dispersion induced by laser chirping.

49. The optical receiver according to claim 18, wherein said means for digitally processing the digital electrical signal comprises means for decoding a convolutional code.

50. The optical receiver according to claim 18, wherein said means for digitally processing the digital electrical signal comprises means for decoding a trellis code.

51. The optical receiver according to claim 18, wherein said means for digitally processing the digital electrical signal comprises means for decoding a block code.