Methods and apparatus for Raman crosstalk reduction via idle data pattern control

1. A method for reducing Raman crosstalk in a wavelength-division-multiplexing optical fiber transmission system for transmitting a multiplex of channels, comprising:

sending idle data over one or more of the channels to maintain an optical link, said idle data having an idle data pattern; and

controlling the idle data pattern of at least one of said channels such that a power spectral density of a signal carried by said at least one channel is shifted in order to reduce Raman crosstalk between the channels,

wherein: the power spectral density is shifted away from lower frequencies of the channel.

2. A method in accordance with claim 1 , wherein:

the idle data pattern of each channel is controlled such that the power spectral density of the signal carried by each channel is shifted in order to reduce Raman crosstalk between the channels.

3. A method in accordance with claim 1 , wherein:

said optical fiber transmission system comprises a Passive Optical Network (PON).

4. A method in accordance with claim 1 , wherein:

said optical fiber transmission system comprises one of: (a) an Asynchronous Transfer Mode (ATM) based Passive Optical Network (APON); (b) an Ethernet-based Passive Optical Network (EPON); and (c) a Gigabit Passive Optical Network (G-PON).

5. A method in accordance with claim 4 , wherein:

(a) said APON comprises an APON with video overlay (B-PON);

(b) said EPON comprises an EPON with video overlay; and

(c) said GPON comprises a G-PON with video overlay.

6. A method in accordance with claim 1 , wherein:

each channel comprises one of a digital data channel or an analog video channel.

7. A method in accordance with claim 1 , wherein:

the idle data comprises one of: (a) idle data cells; (b) idle data frames; and (c) idle data fragments, each of which has a header and a payload; and

said idle data pattern of the at least one channel is controlled by modifying at least a portion of the payload of the idle data.

8. A method in accordance with claim 7 , wherein:

said modifying of the payload comprises scrambling the payload to achieve a payload having a desired idle data pattern.

9. A method in accordance with claim 1 , wherein:

the idle data comprises one of: (a) idle data cells; (b) idle data frames; and (c) idle data fragments, each of which has a header and a payload; and

said idle data pattern of the at least one channel is controlled by replacing at least a portion of the payload of the idle data.

10. A method in accordance with claim 9 , further comprising:

scrambling the idle data header and payload; and

replacing at least a portion of the scrambled payload to provide a desired idle data pattern.

11. A method in accordance with claim 9 , further comprising:

scrambling the idle data header and payload; and

re-coding at least a portion of the scrambled payload to provide a desired idle data pattern.

12. A method in accordance with claim 11 , wherein:

the desired idle data pattern resembles a Manchester coded data signal.

13. A method for reducing Raman crosstalk in a wavelength-division-multiplexing optical fiber transmission system for transmitting a multiplex of channels, comprising:

sending idle data over one or more of the channels to maintain an optical link, said idle data having an idle data pattern; and

controlling the idle data pattern of at least one of said channels such that a power spectral density of a signal carried by said at least one channel is shifted in order to reduce Raman crosstalk between the channels,

wherein: the power spectral density is shifted towards unused frequencies of the channel.

14. A method in accordance with claim 13 , wherein:

the idle data pattern of each channel is controlled such that the power spectral density of the signal carried by each channel is shifted in order to reduce Raman crosstalk between the channels.

15. A method in accordance with claim 13 , wherein:

said optical fiber transmission system comprises a Passive Optical Network (PON).

16. A method in accordance with claim 13 , wherein:

said optical fiber transmission system comprises one of: (a) an Asynchronous Transfer Mode (ATM) based Passive Optical Network (APON); (b) an Ethernet-based Passive Optical Network (EPON); and (c) a Gigabit Passive Optical Network (G-PON).

17. A method in accordance with claim 16 , wherein:

(a) said APON comprises an APON with video overlay (B-PON);

(b) said EPON comprises an EPON with video overlay; and

(c) said GPON comprises a G-PON with video overlay.

18. A method in accordance with claim 13 , wherein:

each channel comprises one of a digital data channel or an analog video channel.

19. A method in accordance with claim 13 , wherein:

the idle data comprises one of: (a) idle data cells; (b) idle data frames; and (c) idle data fragments, each of which has a header and a payload; and

said idle data pattern of the at least one channel is controlled by modifying at least a portion of the payload of the idle data.

20. A method in accordance with claim 19 , wherein:

said modifying of the payload comprises scrambling the payload to achieve a payload having a desired idle data pattern.

21. A method in accordance with claim 13 , wherein:

the idle data comprises one of: (a) idle data cells; (b) idle data frames; and (c) idle data fragments, each of which has a header and a payload; and

said idle data pattern of the at least one channel is controlled by replacing at least a portion of the payload of the idle data.

22. A method in accordance with claim 21 , further comprising:

scrambling the idle data header and payload; and

replacing at least a portion of the scrambled payload to provide a desired idle data pattern.

23. A method in accordance with claim 21 , further comprising:

scrambling the idle data header and payload; and

re-coding at least a portion of the scrambled payload to provide a desired idle data pattern.

24. A method in accordance with claim 23 , wherein:

the desired idle data pattern resembles a Manchester coded data signal.

25. An apparatus for reducing Raman crosstalk in a wavelength-division-multiplexing optical fiber transmission system for transmitting a multiplex of channels, comprising:

a transmitter for sending idle data over one or more of the channels to maintain an optical link, said idle data having an idle data pattern; and

a processor for controlling the idle data pattern of at least one of said channels such that a power spectral density of a signal carried by said at least one channel is shifted in order to reduce Raman crosstalk between the channels,

wherein: the power spectral density is shifted away from lower frequencies of the channel.

26. An apparatus in accordance with claim 25 , wherein:

the idle data pattern of each channel is controlled such that the power spectral density of the signal carried by each channel is shifted in order to reduce Raman crosstalk between the channels.

27. An apparatus in accordance with claim 25 , wherein:

said optical fiber transmission system comprises a Passive Optical Network (PON).

28. An apparatus in accordance with claim 25 , wherein:

said optical fiber transmission system comprises one of: (a) an Asynchronous Transfer Mode (ATM) based Passive Optical Network (APON); (b) an Ethernet-based Passive Optical Network (EPON); and (c) a Gigabit Passive Optical Network (G-PON).

29. An apparatus in accordance with claim 28 , wherein:

(a) said APON comprises an APON with video overlay (B-PON);

(b) said EPON comprises an EPON with video overlay; and

(c) said GPON comprises a G-PON with video overlay.

30. An apparatus in accordance with claim 25 , wherein:

each channel comprises one of a digital data channel or an analog video channel.

31. An apparatus in accordance with claim 25 , wherein:

the idle data comprises at least one of: (a) idle data cells; (b) idle data frames; and (c) idle data fragments, each of which has a header and a payload; and

said idle data pattern of the at least one channel is controlled by modifying at least a portion of the payload of the idle data.

32. An apparatus in accordance with claim 31 , wherein:

said modifying of the payload comprises scrambling the payload to achieve a payload having a desired idle data pattern.

33. An apparatus in accordance with claim 25 , wherein:

the idle data comprises at least one of: (a) idle data cells; (b) idle data frames; and (c) idle data fragments, each of which has a header and a payload; and

said idle data pattern of the at least one channel is controlled by replacing at least a portion of the payload of the idle data.

34. An apparatus in accordance with claim 33 , further comprising:

scrambling the idle data header and payload; and

replacing at least a portion of the scrambled payload to provide a desired idle data pattern.

35. An apparatus in accordance with claim 33 , further comprising:

scrambling the idle data header and payload; and

re-coding at least a portion of the scrambled payload to provide a desired idle data pattern.

36. An apparatus in accordance with claim 35 , wherein:

the desired idle data pattern resembles a Manchester coded data signal.

37. An apparatus for reducing Raman crosstalk in a wavelength-division-multiplexing optical fiber transmission system for transmitting a multiplex of channels, comprising:

a transmitter for sending idle data over one or more of the channels to maintain an optical link, said idle data having an idle data pattern; and

a processor for controlling the idle data pattern of at least one of said channels such that a power spectral density of a signal carried by said at least one channel is shifted in order to reduce Raman crosstalk between the channels,

wherein: the power spectral density is shifted towards unused frequencies of the channel.

38. An apparatus in accordance with claim 37 , wherein:

the idle data pattern of each channel is controlled such that the power spectral density of the signal carried by each channel is shifted in order to reduce Raman crosstalk between the channels.

39. An apparatus in accordance with claim 37 , wherein:

said optical fiber transmission system comprises a Passive Optical Network (PON).

40. An apparatus in accordance with claim 37 , wherein:

said optical fiber transmission system comprises one of: (a) an Asynchronous Transfer Mode (ATM) based Passive Optical Network (APON); (b) an Ethernet-based Passive Optical Network (EPON); and (c) a Gigabit Passive Optical Network (G-PON).

41. An apparatus in accordance with claim 40 , wherein:

(a) said APON comprises an APON with video overlay (B-PON);

(b) said EPON comprises an EPON with video overlay; and

(c) said GPON comprises a G-PON with video overlay.

42. An apparatus in accordance with claim 37 , wherein:

each channel comprises one of a digital data channel or an analog video channel.

43. An apparatus in accordance with claim 37 , wherein:

the idle data comprises at least one of: (a) idle data cells; (b) idle data frames; and (c) idle data fragments, each of which has a header and a payload; and

said idle data pattern of the at least one channel is controlled by modifying at least a portion of the payload of the idle data.

44. An apparatus in accordance with claim 43 , wherein:

said modifying of the payload comprises scrambling the payload to achieve a payload having a desired idle data pattern.

45. An apparatus in accordance with claim 37 , wherein:

the idle data comprises at least one of: (a) idle data cells; (b) idle data frames; and (c) idle data fragments, each of which has a header and a payload; and

said idle data pattern of the at least one channel is controlled by replacing at least a portion of the payload of the idle data.

46. An apparatus in accordance with claim 45 , further comprising:

scrambling the idle data header and payload; and

replacing at least a portion of the scrambled payload to provide a desired idle data pattern.

47. An apparatus in accordance with claim 45 , further comprising:

scrambling the idle data header and payload; and

re-coding at least a portion of the scrambled payload to provide a desired idle data pattern.

48. An apparatus in accordance with claim 47 , wherein:

the desired idle data pattern resembles a Manchester coded data signal.