Optical wavelength multiplex transmission method and optical dispersion compensation method

• US 6,243,176 B1
• Filed: 08/25/1997
• Issued: 06/05/2001
• Est. Priority Date: 08/10/1993
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Miyata, Hideyuki, Onaka, Hiroshi, Ishikawa, George, Sekiya, Motoyoshi, Otsuka, Kazue
• Primary Examiner(s): PASCAL, LESLIE C
• Application Number:
  US08/917,292
• Time in Patent Office: 1,380 Days
• Field of Search: 359/124, 359/161, 359/127, 359/173, 359/179, 359/114, 359/115, 385/24, 385/122, 385/123
• US Class Current: 398/141
• CPC Class Codes: G02B 6/29377 controlling dispersion around 1550 nm, i.e. S, C, L and U bands from 1460-1675 nm
• CPC Class Codes: G02B 6/4215 the intermediate optical elements being wavelength selective optical elements, e.g. variable wavelength optical modules or wavelength lockers G02B6/4246 takes precedence
• CPC Class Codes: H04B 10/25133 including a lumped electrical or optical dispersion compensator H04B10/2519, H04B10/2525 takes precedence
• CPC Class Codes: H04B 10/2525 using dispersion-compensating fibres
• CPC Class Codes: H04B 10/25253 with dispersion management, i.e. using a combination of different kind of fibres in the transmission system
• CPC Class Codes: H04B 10/255 Self-phase modulation [SPM]
• CPC Class Codes: H04B 10/2563 Four-wave mixing [FWM]
• CPC Class Codes: H04B 2210/252 after the transmission line, i.e. post-compensation
• CPC Class Codes: H04B 2210/254 before the transmission line, i.e. pre-compensation
• CPC Class Codes: H04B 2210/258 treating each wavelength or wavelength band separately
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/0224 Irregular wavelength spacing, e.g. to accommodate interference to all wavelengths
• CPC Class Codes: H04J 14/0305 in end terminals

Abstract

The invention provides an optical wavelength multiplex transmission method wherein a band in the proximity of a zero dispersion wavelength of an optical fiber is used and optical signals are disposed at efficient channel spacings taking an influence of the band, the wavelength dispersion and the four wave mixing into consideration to realize an optical communication system of an increased capacity which is not influenced by crosstalk by FWM. When optical signals of a plurality of channels having different wavelengths are to be multiplexed and transmitted using an optical fiber, a four wave mixing suppressing guard band of a predetermined bandwidth including the zero-dispersion wavelength λθ of the optical fiber is set, and signal light waves of the plurality of channels to be multiplexed are arranged on one of the shorter wavelength side and the longer wavelength side outside the guard band.

Claims

1. An optical communication system which provides a plurality of signal channels for transmitting optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth through an optical fiber transmission line, wherein

the optical fiber transmission line has a zero dispersion wavelength,

each of the plurality of signal channels is arranged to a longer wavelength side of the zero dispersion wavelength, and

dispersion given to the optical signals transmitted through the signal channels is collectively compensated by a dispersion compensator.

2. An optical communication system according to claim 1, wherein the plurality of signal channels are equally spaced.

3. An optical communication system according to claim 1, wherein the plurality of signal channels are unequally spaced.

4. An optical communication system according to claim 1, wherein

a four wave mixing suppressing guard band is provided so as to have a predetermined bandwidth and include the zero dispersion wavelength, and

each signal channel is arranged outside of the guard band.

5. An optical communication system according to claim 1, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

6. An optical communication system according to claim 1, wherein the dispersion given to all the optical signals transmitted through the signal channels is collectively compensated by the dispersion compensator.

7. An optical communication system according to claim 1, wherein channel spacing between a pair of adjacent signal channels is set to an integer multiple of a minimum channel spacing defined in terms of an optical frequency or an optical wavelength.

8. An optical communication system according to claim 7, wherein the minimum channel spacing is 50 GHz.

9. An optical network, comprising:

an optical fiber transmission line having a zero dispersion wavelength, wherein

a plurality of signal channels for transmitting, through the optical fiber transmission line, optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth are provided, and are each arranged to a longer wavelength side of the zero dispersion wavelength, and

dispersion given to the optical signals transmitted through the signal channels is collectively compensated by a dispersion compensator.

10. An optical network according to claim 9, wherein the plurality of signal channels are equally spaced.

11. An optical network according to claim 9, wherein the plurality of signal channels are unequally spaced.

12. An optical network according to claim 9, wherein

a four wave mixing suppressing guard band is provided so as to have a predetermined bandwidth and include the zero dispersion wavelength, and

each signal channel is arranged outside of the guard band.

13. An optical network according to claim 9, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

14. An optical network according to claim 9, wherein the dispersion given to all the optical signals transmitted through the signal channels is collectively compensated by the dispersion compensator.

15. An optical network according to claim 9, wherein channel spacing between a pair of adjacent signal channels is set to an integer multiple of a minimum channel spacing defined in terms of an optical frequency or an optical wavelength.

16. An optical network according to claim 15, wherein the minimum channel spacing is 50 GHz.

17. An optical communication system which provides a plurality of signal channels for transmitting optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth through an optical fiber transmission line, wherein

the optical fiber transmission line has a zero dispersion wavelength,

each of the plurality of signal channels is arranged to a shorter wavelength side of the zero dispersion wavelength, and

dispersion given to the optical signals transmitted through the signal channels is collectively compensated by a dispersion compensator.

18. An optical communication system according to claim 17, wherein the plurality of signal channels are equally spaced.

19. An optical communication system according to claim 17, wherein the plurality of signal channels are unequally spaced.

20. An optical communication system according to claim 17, wherein

a four wave mixing suppressing guard band is provided so as to have a predetermined bandwidth and include the zero dispersion wavelength, and

each signal channel is arranged outside of the guard band.

21. An optical communication system according to claim 17, wherein the dispersion given to all the optical signals transmitted through the signal channels is collectively compensated by the dispersion compensator.

22. An optical communication system according to claim 17, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

23. An optical communication system according to claim 17, wherein channel spacing between a pair of adjacent signal channels is set to an integer multiple of a minimum channel spacing defined in terms of an optical frequency or an optical wavelength.

24. An optical communication system according to claim 23, wherein the minimum channel spacing is 50 GHz.

25. An optical network, comprising:

an optical fiber transmission line having a zero dispersion wavelength, wherein

a plurality of signal channels for transmitting, through the optical transmission line, optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth are provided, and are each arranged to a shorter wavelength side of the zero dispersion wavelength, and

dispersion given to the optical signals transmitted through the signal channels is collectively compensated by a dispersion compensator.

26. An optical network according to claim 25, wherein the plurality of signal channels are equally spaced.

27. An optical network according to claim 25, wherein the plurality of signal channels are unequally spaced.

28. An optical network according to claim 25, wherein

a four wave mixing suppressing guard band is provided so as to have a predetermined bandwidth and include the zero dispersion wavelength, and

each signal channel is arranged outside of the guard band.

29. An optical network according to claim 25, wherein the dispersion given to all the optical signals transmitted through the signal channels is collectively compensated by the dispersion compensator.

30. An optical network according to claim 25, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

31. An optical network according to claim 25, wherein channel spacing between a pair of adjacent signal channels is set to an integer multiple of a minimum channel spacing defined in terms of an optical frequency or an optical wavelength.

32. An optical network according to claim 31, wherein the minimum channel spacing is 50 GHz.

33. An optical communication system which provides a plurality of signal channels for transmitting optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth through an optical fiber transmission line, wherein

the optical fiber transmission line has a zero dispersion wavelength,

the plurality of signal channels are arranged to both a longer wavelength side and a shorter wavelength side of the zero dispersion wavelength, and

dispersion given to the optical signals transmitted through the signal channels is collectively compensated by a dispersion compensator.

34. An optical communication system according to claim 33, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelength are equally spaced.

35. An optical communication system according to claim 33, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are equally spaced.

36. An optical communication system according to claim 33, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelength are unequally spaced.

37. An optical communication system according to claim 33, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are unequally spaced.

38. An optical communication system according to claim 33, wherein

a four wave mixing suppressing guard band is provided so as to have a predetermined bandwidth and include the zero dispersion wavelength, and

each signal channel is arranged outside of the guard band.

39. An optical communication system according to claim 33, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

40. An optical communication system according to claim 33, wherein the dispersion given to all the optical signals transmitted through the signal channels is collectively compensated by the dispersion compensator.

41. An optical communication system according to claim 33, wherein channel spacing between a pair of adjacent signal channels arranged to either the longer wavelength side or the shorter wavelength side of the zero dispersion wavelength is set to an integer multiple of a minimum channel spacing defined in terms of an optical frequency or an optical wavelength.

42. An optical communication system according to claim 41, wherein the minimum channel spacing is 50 GHz.

43. An optical network, comprising:

an optical fiber transmission line having a zero dispersion wavelength, wherein

a plurality of signal channels for transmitting, through the optical fiber transmission line, optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth are provided, and are arranged to both a longer wavelength side and a shorter wavelength side of the zero dispersion wavelength, and

dispersion given to the optical signals transmitted through the signal channels is collectively compensated by a dispersion compensator.

44. An optical network according to claim 43, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelength are equally spaced.

45. An optical network according to claim 43, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are equally spaced.

46. An optical network according to claim 43, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelengths are unequally spaced.

47. An optical network according to claim 43, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are unequally spaced.

48. An optical network according to claim 43, wherein

a four wave mixing suppressing guard band is provided so as to have a predetermined bandwidth and include the zero dispersion wavelength, and

each signal channel is arranged outside of the guard band.

49. An optical network according to claim 43, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

50. An optical network according to claim 43, wherein the dispersion given to all the optical signals transmitted through the signal channels is collectively compensated by the dispersion compensator.

51. An optical network according to claim 43, wherein channel spacing between a pair of adjacent signal channels arranged to either the longer wavelength side or the shorter wavelength side of the zero dispersion wavelength is set to an integer multiple of a minimum channel spacing defined in terms of an optical frequency or an optical wavelength.

52. An optical network according to claim 51, wherein the minimum channel spacing is 50 GHz.

53. An optical communication system which provides a plurality of signal channels for transmission of optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth through an optical fiber transmission line, comprising:

a transmitter producing a plurality of optical signals having different wavelengths;

a multiplexer multiplexing the plurality of optical signals into a wavelength division multiplexed signal transmitted to the optical fiber transmission line;

a demultiplexer demultiplexing the wavelength division multiplexed signal received from the optical fiber transmission line into the plurality of optical signals;

a receiver receiving a respective optical signal from the demultiplexer; and

a dispersion compensator collectively compensating dispersion given to the optical signals transmitted through the signal channels, wherein

each of the plurality of optical signals is associated with one of the plurality of signal channels, and

each of the plurality of signal channels is arranged to a longer wavelength side of a zero dispersion wavelength of the optical fiber transmission line.

54. An optical communication system according to claim 53, wherein the plurality of signal channels are equally spaced.

55. An optical communication system according to claim 53, wherein the plurality of signal channels are unequally spaced.

56. An optical communication system according to claim 53, wherein

a four wave mixing suppressing guard band is provided so as to have a predetermined bandwidth and include the zero dispersion wavelength, and

each signal channel is arranged outside of the guard band.

57. An optical communication system according to claim 53, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

58. An optical communication system according to claim 53, wherein the dispersion compensator collectively compensates dispersion given to all the optical signals transmitted through the signal channels.

59. An optical communication system according to claim 53, wherein channel spacing between a pair of adjacent signal channels is set to an integer multiple of a minimum channel spacing defined in terms of an optical frequency or an optical wavelength.

60. An optical communication system according to claim 59, wherein the minimum channel spacing is 50 GHz.

65. An optical communication system according to claim 54, wherein the dispersion compensator collectively compensates dispersion given to all the optical signals transmitted through the signal channels.

66. An optical communication system according to claim 54, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

61. An optical communication system which provides a plurality of signal channels for transmission of optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth through an optical fiber transmission line, comprising:

a transmitter producing a plurality of optical signals having different wavelengths;

a multiplexer multiplexing the plurality of optical signals into a wavelength division multiplexed signal transmitted to the optical fiber transmission line;

a demultiplexer demultiplexing the wavelength division multiplexed signal received from the optical fiber transmission line into the plurality of optical signals;

a receiver receiving a respective optical signal from the demultiplexer; and

a dispersion compensator collectively compensating dispersion given to the optical signals transmitted through the signal channels, wherein

each of the plurality of optical signals is associated with one of the plurality of signal channels, and

each of the plurality of signal channels is arranged to a shorter wavelength side of a zero dispersion wavelength of the optical fiber transmission line.

62. An optical communication system according to claim 61, wherein the plurality of signal channels are equally spaced.

63. An optical communication system according to claim 61, wherein the plurality of signal channels are unequally spaced.

64. An optical communication system according to claim 61, wherein

a four wave mixing suppressing guard band is provided so as to have a predetermined bandwidth and include the zero dispersion wavelength, and

each signal channel is arranged outside of the guard band.

67. An optical communication system according to claim 61, wherein channel spacing between a pair of adjacent signal channels is set to an integer multiple of a minimum channel spacing defined in terms of an optical frequency or an optical wavelength.

68. An optical communication system according to claim 67, wherein the minimum channel spacing is 50 GHz.

69. An optical communication system which provides a plurality of signal channels for transmission of optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth through an optical fiber transmission line, comprising:

a transmitter producing a plurality of optical signals having different wavelengths;

a multiplexer multiplexing the plurality of optical signals into a wavelength division multiplexed signal transmitted to the optical fiber transmission line;

a demultiplexer demultiplexing the wavelength division multiplexed signal received from the optical fiber transmission line into the plurality of optical signals;

a receiver receiving a respective optical signal from the demultiplexer; and

a dispersion compensator collectively compensating dispersion given to the optical signals transmitted through the signal channels, wherein

each of the plurality of optical signals is associated with one of the plurality of signal channels, and

the plurality of signal channels are arranged to both a longer wavelength side and shorter wavelength side of a zero dispersion wavelength of the optical fiber transmission line.

70. An optical communication system according to claim 69, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelength are equally spaced.

71. An optical communication system according to claim 69, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are equally spaced.

72. An optical communication system according to claim 69, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelength are unequally spaced.

73. An optical communication system according to claim 69, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are unequally spaced.

74. An optical communication system according to claim 69, wherein

a four wave mixing suppressing guard band is provided so as to have a predetermined bandwidth and include the zero dispersion wavelength of the optical transmission line, and

each signal channel is arranged outside of the guard band.

75. An optical communication system according to claim 69, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

76. An optical communication system according to claim 69, wherein the dispersion compensator collectively compensates dispersion given to all the optical signals transmitted through the signal channels.

77. An optical communication system according to claim 69, wherein channel spacing between a pair of adjacent signal channels arranged to either the longer wavelength side or the shorter wavelength side of the zero dispersion wavelength is set to an integer multiple of a minimum channel spacing defined in terms of an optical frequency or an optical wavelength.

78. An optical communication system according to claim 77, wherein the minimum channel spacing is 50 GHz.

79. An optical communication system for transmitting an optical signal through an optical fiber transmission line having a zero dispersion wavelength, comprising:

a plurality of signal channels for transmitting optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth through the optical fiber transmission line, each of the plurality of signal channels being arranged to a longer wavelength side of the zero dispersion wavelength; and

a dispersion compensator collectively compensating for dispersion given to the optical signals transmitted through the signal channels.

80. An optical communication system according to claim 79, wherein the dispersion compensator collectively compensates for the dispersion given to all the optical signals transmitted through the signal channels.

81. An optical communication system according to claim 79, wherein the plurality of signal channels are equally spaced.

82. An optical communication system according to claim 79, further comprising:

a four wave mixing suppressing guard band having a predetermined bandwidth and including the zero dispersion wavelength, each signal channel being arranged outside of the guard band.

83. An optical communication system according to claim 79, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

84. An optical network, comprising:

an optical fiber transmission line having a zero dispersion wavelength;

a plurality of signal channels for transmitting, through the optical fiber transmission line, optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth, each arranged to a longer wavelength side of the zero dispersion wavelength; and

a dispersion compensator collectively compensating for dispersion given to the optical signals transmitted through the signal channels.

85. An optical network according to claim 84, wherein the plurality of signal channels are equally spaced.

86. An optical network according to claim 84, wherein the plurality of signal channels are unequally spaced.

87. An optical network according to claim 84, further comprising:

a four wave mixing suppressing guard band having a predetermined bandwidth and including the zero dispersion wavelength, each signal channel being arranged outside of the guard band.

88. An optical network according to claim 84, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

89. An optical network according to claim 84, wherein the dispersion compensator collectively compensates for the dispersion given to all the optical signals transmitted through the signal channels.

90. An optical communication system for transmitting an optical signal through an optical fiber transmission line having a zero dispersion wavelength, comprising:

a plurality of signal channels for transmitting optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth through the optical fiber transmission line, each of the plurality of signal channels being arranged to a shorter wavelength side of the zero dispersion wavelength; and

a dispersion compensator collectively compensating dispersion given to the optical signals transmitted through the signal channels.

91. An optical communication system according to claim 90, wherein the plurality of signal channels are equally spaced.

92. An optical communication system according to claim 90, further comprising:

a four wave mixing suppressing guard band having a predetermined bandwidth and including the zero dispersion wavelength, each signal channel being arranged outside of the guard band.

93. An optical communication system according to claim 90, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

94. An optical communication system according to claim 90, wherein the plurality of signal channels are unequally spaced.

95. An optical communication system according to claim 90, wherein the dispersion compensator collectively compensates the dispersion given to the optical signals transmitted through the signal channels.

100. An optical network according to claim 95, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

96. An optical network, comprising:

an optical fiber transmission line having a zero dispersion wavelength;

a plurality of signal channels for transmitting, through the optical transmission line, optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth, each arranged to a shorter wavelength side of the zero dispersion wavelength; and

a dispersion compensator collectively compensating dispersion given to the optical signals transmitted through the signal channels.

97. An optical network according to claim 96, further comprising:

a four wave mixing suppressing guard band having a predetermined bandwidth and including the zero dispersion wavelength, each signal channel being arranged outside of the guard band.

98. An optical network according to claim 96, wherein the dispersion compensator collectively compensates the dispersion given to the optical signals transmitted through the signal channels.

99. An optical network according to claim 96, wherein the plurality of signal channels are equally spaced.

101. An optical network according to claim 96, wherein the plurality of signal channels are unequally spaced.

102. An optical communication system for transmitting an optical signal through an optical fiber transmission line having a zero dispersion wavelength, comprising:

a plurality of signal channels for transmitting optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth through the optical fiber transmission line, the plurality of signal channels being arranged to both a longer wavelength side and a shorter wavelength side of the zero dispersion wavelength; and

a dispersion compensator collectively compensating dispersion given to the optical signals transmitted through the signal channels.

103. An optical communication system according to claim 102, wherein

the optical signals include a plurality of first optical signals and a plurality of second optical signals of which wavelengths are longer than wavelengths of the first optical signals, and

the dispersion compensator includes a first dispersion compensator which collectively compensates dispersion given to the first optical signals and a second dispersion compensator which collectively compensates dispersion given to the second optical signals.

104. An optical communication system according to claim 102, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are equally spaced.

105. An optical communication system according to claim 102, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelength are unequally spaced.

106. An optical communication system according to claim 102, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are unequally spaced.

107. An optical communication system according to claim 102, further comprising:

a four wave mixing suppressing guard band having a predetermined bandwidth and include the zero dispersion wavelength, each signal channel being arranged outside of the guard band.

108. An optical communication system according to claim 102, wherein the dispersion compensator compensates the dispersion given to all the optical signals transmitted through the signal channels.

109. An optical communication system according to claim 102, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelength are equally spaced.

110. An optical network comprising:

an optical fiber transmission line having a zero dispersion wavelength;

a plurality of signal channels for transmitting, through the optical fiber transmission line, optical signals having different wavelengths within a wavelength-division-multiplexing signal bandwidth, and are arranged to both a longer wavelength side and a shorter wavelength side of the zero dispersion wavelength; and

a dispersion compensator collectively compensating dispersion given to the optical signals transmitted through the signal channels.

111. An optical network according to claim 110, wherein the dispersion compensator compensates the dispersion given to all the optical signals transmitted through the signal channels.

112. An optical network according to claim 110, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelength are equally spaced.

113. An optical network according to claim 110, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are equally spaced.

114. An optical network according to claim 110, wherein the signal channels arranged to the longer wavelength side of the zero dispersion wavelengths are unequally spaced.

115. An optical network according to claim 110, wherein the signal channels arranged to the shorter wavelength side of the zero dispersion wavelength are unequally spaced.

116. An optical network according to claim 110, further comprising:

a four wave mixing suppressing guard band having a predetermined bandwidth and including the zero dispersion wavelength, each signal channel being arranged outside of the guard band.