All band amplifier

• US 6,574,037 B2
• Filed: 01/22/2001
• Issued: 06/03/2003
• Est. Priority Date: 06/16/1998
• Status: Expired due to Term

• Current Assignee: Neptune Subsea IP Ltd. (Xtera Topco Ltd.)
• Original Assignee: Xtera Communications Incorporated (Xtera Topco Ltd.)
• Inventors: Islam, Mohammed N., Dewilde, Carl, Freeman, Michael
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Hughes, Deandra M.
• Application Number:
  US09/768,367
• Publication Number:
  US 20020063948A1
• Time in Patent Office: 862 Days
• Field of Search: 359/334, 359/337.4
• US Class Current: 359/334
• CPC Class Codes: H01S 3/06758 Tandem amplifiers
• CPC Class Codes: H01S 3/094015 with pump light recycling, i.e. with reinjection of the unused pump light back into the fiber, e.g. by reflectors or circulators
• CPC Class Codes: H01S 3/302 in an optical fibre
• 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 10/2916 using Raman or Brillouin amplifiers
• CPC Class Codes: H04B 2210/003 Devices including multiple stages, e.g., multi-stage optical amplifiers or dispersion compensators

Abstract

A Raman amplifier apparatus includes an optical transmission line with an input to receive an optical signal, an output that passes the optical signal, a first Raman gain fiber and a second Raman gain fiber. A first WDM is positioned between the second Raman gain fiber and the output. A first set of pump wavelengths is input to the first WDM. A second WDM is positioned between the first and second Raman gain fibers. A second set of pump wavelengths is input to the second WDM. At least a portion of the first set of pump wavelengths are different than the second set of pump wavelengths. The first and second set of pump wavelengths propagate in the same direction.

Claims

1. A method of amplification, comprising:

providing a Raman amplifier apparatus including an optical transmission line with an input to receive an optical signal, an output that passes the optical signal, a first Raman gain fiber and a second Raman gain fiber;

introducing into the input a signal with multiple wavelengths;

amplifying the signal in the Raman amplifier apparatus, wherein a majority of longer wavelengths of the signal are amplified before shorter wavelengths of the signal are amplified; and

producing an amplifier output.

2. The method of claim 1, wherein the signal is amplified and wherein at least a portion of a dispersion associated with the signal is compensated in the Raman amplifier apparatus.

3. The method of claim 1, wherein the amplifier amplifies more than 35 nm of bandwidth.

4. The method of claim 1, wherein the amplifier amplifies more than 50 nm of bandwidth.

5. The method of claim 1, wherein the signal propagates in an upstream direction from the input to the output of the Raman amplifier apparatus, and wherein one or more pump wavelengths propagate in a downstream direction.

6. The method of claim 5, wherein a first pump source provides a first plurality of pump wavelengths to be introduced to the first Raman gain fiber and a second pump source provides a second plurality of pump wavelengths to be introduced to the second Raman gain fiber.

7. The method of claim 1, wherein a gain flatness of the Raman amplifier apparatus is optimized by pump wavelengths, pump powers and a number of pumps.

8. The method of claim 1, wherein a gain flatness of the Raman amplifier apparatus is optimized by at least one of a length of the first Raman gain fiber and a length of the second Raman gain fiber.

9. The method of claim 1, wherein a gain flatness of the Raman amplifier apparatus is optimized by a gain flattening filter.

10. The method of claim 5, wherein the at least one of the first and second pluralities of pump wavelengths collectively produce a wavelength range λ

_p comprising at least 60 nanometers.

11. The method of claim 10, wherein the wavelength range λ

_p includes 1250 nm to 1550 nm.

12. The method of claim 10, wherein the wavelength range λ

_p includes 1300 nm to 1530 nm.

13. The method of claim 1, wherein the optical signal has a wavelength range λ

_S including 1400 to 1650 nm.

14. The method of claim 1, wherein the optical signal has a wavelength range λ

_S including 1430 to 1630 nm.

15. The method of claim 1, wherein the signal travels from the first Raman gain fiber to the second Raman gain fiber, and the majority of the longer wavelengths of the signal are amplified more in the first Raman gain fiber than in the second Raman gain fiber.

16. The method of claim 1, wherein the signal travels from the first Raman gain fiber to the second Raman gain fiber, and the majority of the shorter wavelengths of the signal are amplified more in the second Raman gain fiber than in the first Raman gain fiber.

23. The method of claim 1, wherein amplifying the optical signal comprises imparting a net gain to at least a portion of the optical signal.

17. A method of amplification, comprising:

providing an amplifier apparatus including a first pump source coupled to a first port of an optical transmission line, a second pump source coupled to a second port of the optical transmission line, an output that passes an optical signal, a first gain fiber and a second gain fiber;

introducing signals to an input of the optical transmission line;

pumping the first gain fiber with a second set of pump wavelengths and the second gain fiber with a first set of pump wavelengths;

wherein at least a portion of the first set of pump wavelengths is different than the second set of pump wavelengths;

wherein a majority of longer wavelengths of the signal are amplified before shorter wavelengths of the signal are amplified; and

producing an amplifier output.

18. The method of claim 17, wherein a gain variation over a bandwidth of the optical signal comprising at least 80 nm is less than 5 dB.

19. The method of claim 17, wherein the first and second sets of pump wavelengths collectively produce a wavelength range λ

_p spanning at least 60 nanometers.

20. The method of claim 17, wherein the optical signal propagates in an upstream direction from the input to the output of the amplifier apparatus, and the first and second sets of pump wavelengths propagate in a downstream direction.

21. The method of claim 17, wherein the wavelengths of the optical signal are within a wavelength range λ

_S of 1400 to 1650 nm.

22. The method of claim 17, wherein the wavelengths of the optical signal are within a wavelength range λ

_S of 1430 to 1630 nm.

24. The method of claim 17, further comprising imparting a net gain to at least a portion of the optical signal.

25. A method of amplification, comprising:

receiving a multiple wavelength optical signal at a Raman amplifier apparatus comprising an input to receive the optical signal, an output that passes at least a portion of the optical signal, a first Raman gain fiber and a second Raman gain fiber;

amplifying the signal in the Raman amplifier apparatus, wherein a majority of longer wavelengths of the signal are amplified before a majority of shorter wavelengths of the signal are amplified; and

producing an amplifier output.

26. The method of claim 25, wherein the signal is amplified and wherein at least a portion of a dispersion associated, with the signal is compensated in the Raman amplifier apparatus.

27. The method of claim 25, wherein the amplifier amplifies more than 35 nm of bandwidth.

28. The method of claim 25, wherein the amplifier amplifies more than 50 nm of bandwidth.

29. The method of claim 25, wherein the signal propagates in an upstream direction from the input to the output of the Raman amplifier apparatus, and wherein one or more pump wavelengths propagate in a downstream direction.

30. The method of claim 25, wherein a first pump source provides a first plurality of pump wavelengths to be introduced to the first Raman gain fiber and a second pump source provides a second plurality of pump wavelengths to be introduced to the second Raman gain fiber.

31. The method of claim 25, wherein a gain flatness of the Raman amplifier apparatus is optimized by pump wavelengths, pump powers and a number of pumps.

32. The method of claim 25, wherein a gain flatness of the Raman amplifier apparatus is optimized by at least one of a length of the first Raman gain fiber and a length of the second Raman gain fiber.

33. The method of claim 25, wherein a gain flatness of the Raman amplifier apparatus is optimized by a gain flattening filter.

34. The method of claim 25, wherein each one of the first and second gain fibers is pumped by more than one wavelength and wherein at least one of the more than one wavelengths pumping the first or second gain fibers collectively produces a wavelength range λ

_p comprising at least 60 nanometers.

35. The method of claim 25, wherein the wavelength range λ

_p includes 1250 nm to 1550 nm.

36. The method of claim 25, wherein the wavelength range λ

_p includes 1300 nm to 1530 nm.

37. The method of claim 25, wherein the optical signal has a wavelength range λ

_S including 1400 to 1650 nm.

38. The method of claim 25, wherein the optical signal has a wavelength range λ

_S including 1430 to 1630 nm.

39. The method of claim 25, wherein the signal travels from the first Raman gain fiber to the second Raman gain fiber, and the majority of the longer wavelengths of the signal are amplified more in the first Raman gain fiber than in the second Raman gain fiber.

40. The method of claim 25, wherein the signal travels from the first Raman gain fiber to the second Raman gain fiber, and the majority of the shorter wavelengths of the signal are amplified more in the second Raman gain fiber than in the first Raman gain fiber.

41. The method of claim 25, wherein amplifying the optical signal comprises imparting a net gain to at least a portion of the optical signal.

42. An optical amplifier including a Raman amplifier apparatus comprising:

an input operable to receive a multiple wavelength optical signal;

an output that passes at least a portion of the optical signal;

a first Raman gain fiber; and

a second Raman gain fiber;

wherein the first and second Raman gain fibers are pumped so as to amplify the signal in the Raman amplifier apparatus, wherein a majority of longer wavelengths of the signal are amplified before a majority of shorter wavelengths of the signal are amplified.

43. The amplifier of claim 42, wherein the signal is amplified and wherein at least a portion of a dispersion associated with the signal is compensated in the Raman amplifier apparatus.

44. The amplifier of claim 42, wherein the optical signal comprises a bandwidth of more than 35 nm.

45. The amplifier of claim 42, wherein the optical signal comprises a bandwidth of more than 50 nm.

46. The amplifier of claim 42, wherein each of the first and second gain fibers is pumped by more than one pump wavelength.

47. The amplifier of claim 46, wherein the one or more pump wavelengths pumping at least one of the first and second gain fibers comprise a plurality of pump wavelengths that collectively produce a wavelength range λ

_p comprising at least 60 nanometers.

48. The amplifier of claim 47, wherein the wavelength range λ

_p includes 1250 nm to 1550 nm.

49. The amplifier of claim 47, wherein the wavelength range λ

_p, includes 1300 nm to 1530 nm.

50. The amplifier of claim 42, wherein the signal propagates in an upstream direction from the input to the output of the Raman amplifier apparatus, and wherein one or more pump wavelengths propagate in a downstream direction.

51. The amplifier of claim 42, wherein a first pump source provides a first plurality of pump wavelengths to be introduced to the first Raman gain fiber and a second pump source provides a second plurality of pump wavelengths to be introduced to the second Raman gain fiber.

52. The amplifier of claim 42, wherein a gain flatness of the Raman amplifier apparatus is optimized by a section of pump wavelengths, pump powers and a number of pumps.

53. The amplifier of claim 42, wherein a gain flatness of the Raman amplifier apparatus is optimized by selection at least one of a length of the first Raman gain fiber and a length of the second Raman gain fiber.

54. The amplifier of claim 42, wherein a gain flatness of the Raman amplifier apparatus is improved through use of a gain flattening filter coupled to the Raman amplifier apparatus.

55. The amplifier of claim 42, wherein the optical signal has a wavelength range λ

_s including 1400 to 1650 nm.

56. The amplifier of claim 42, wherein the optical signal has a wavelength range λ

_S including 1430 to 1630 nm.

57. The amplifier of claim 42, wherein the signal travels from the first Raman gain fiber to the second Raman gain fiber, and the majority of the longer wavelengths of the signal are amplified more in the first Raman gain fiber than in the second Raman gain fiber.

58. The amplifier of claim 42, wherein the signal travels from the first Raman gain fiber to the second Raman gain fiber, and the majority of the shorter wavelengths of the signal are amplified more in the second Raman gain fiber than in the first Raman gain fiber.

59. The amplifier of claim 42, further comprising a third Raman gain fiber coupled between the first Raman gain fiber and the second Raman gain fiber.

60. The amplifier of claim 42, wherein amplifying the optical signal comprises imparting a net gain to at least a portion of the optical signal.