USRE38086EExpiredUtility

Dispersion compensating fiber and optical transmission system including the same

Assignee: SUMITOMO ELECTRIC INDUSTRIESPriority: Apr 15, 1996Filed: Nov 17, 2000Granted: Apr 22, 2003

Est. expiryApr 15, 2016(expired)· nominal 20-yr term from priority

Inventors:Masashi Onishi Hiroo Kanamori Masayuki Nishimura Tomonori Kashiwada Yasushi Koyano

G02B 6/02285G02B 6/02261C03B 37/014G02B 6/0283G02B 6/0228G02B 6/29377G02B 6/02004G02B 6/03644G02B 6/0286G02B 6/03611C03B 2203/36H01S 3/06729H01S 3/302C03B 2203/22G02B 6/03627G02B 6/0281

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Claims

Abstract

The present invention relates to a dispersion compensating fiber for improving a transmission system with it in total chromatic dispersion and dispersion slope in the 1.55 mum wavelength band. The dispersion compensating fiber according to the present invention is characterized by having the following characteristics for light in the 1.55 mum wavelength band: chromatic dispersion not less than -40 ps/km/nm and not more than 0 ps/km/nm; dispersion slope not less than -0.5 ps/km/nm2 and not more than -0.1 ps/km/nm2; transmission loss not more than 0.5 dB/km; polarization mode dispersion not more than 0.7 ps.km-½; mode field diameter not less than 4.5 mum and not more than 6.5 mum; cut-off wavelength not less than 0.7 mum and not more than 1.7 mum in the length of 2 m; and bending loss at the diameter of 20 mm, not more than 100 dB/m. The dispersion compensating fiber is optically connected with a dispersion shifted fiber as a compensated object at a ratio of appropriate lengths, which can improve the system including the dispersion compensating fiber in the total chromatic dispersion and dispersion slope of the system in the 1.55 mum band.

Claims

exact text as granted — not AI-modified

What is claimed is:

1. A dispersion compensating fiber having the following characteristics for light in the 1.55 μm wavelength band:
chromatic dispersion not less than −40 ps/km/nm and not more than 0 ps/km/nm 2 ;
dispersion slope not less than −0.5 ps/km/nm 2 and not more than −0.1 ps/km/nm 2 ;
transmission loss not more than 0.5 dB/km;
polarization mode dispersion not more than 0.7 ps.km −½ ;
mode field diameter not less than 4.5 μm and not more than 6.5 μm;
cut-off wavelength not less than 0.7 μm and not more than 1.7 μm in the length of 2 m; and
bending loss at the diameter of 20 mm, not more than 100 dB/m.

2. The dispersion compensating fiber according to claim 1 , said dispersion compensating fiber being a silica-based glass fiber, comprising at least:
a core region having a predetermined refractive index, said core region having an outer diameter not less than 3.5 μm and not more than 6.0 μm;
an inside cladding region provided on the periphery of said core region and having a lower refractive index than said core region, wherein a ratio of the outer diameter of said core region to an outer diameter of said inside cladding region is not less than 0.3 and not more than 0.5; and
an outside cladding region provided on the periphery of said inside cladding region and having a higher refractive index than said inside cladding region and a lower refractive index than said core region,
wherein a relative refractive index difference between said outside cladding region and a portion having a maximum refractive index in said core region is not less than 0.6% and not more than 1.4%, and
wherein a relative refractive index difference between said outside cladding region and a portion having a minimum refractive index in said inside cladding region is not less than 0.25% and not more than 0.65%.

3. The dispersion compensating fiber according to claim 2 , wherein said core region is doped with the germanium element and said inside cladding region is doped with the fluorine element.

4. The dispersion compensating fiber according to claim 3 , wherein said outside cladding region is doped with the fluorine element.

5. The dispersion compensating fiber according to claim 2 , wherein said core region is doped with the erbium element.

6. An optical transmission system having the total dispersion slope not less than −0.02 ps/km/nm 2 and not more than 0.05 ps/km/nm 2 for light in the 1.5 μm wavelength band, said optical transmission system comprising:
the dispersion compensating fiber according to claim 5 ;
a third optical fiber optically connected with said dispersion compensating fiber and forming a part of a transmission line;
an excitation light source for outputting exciting light for exciting the erbium element in said dispersion compensating fiber, to said dispersion compensating fiber; and
an optical coupler for optically coupling said excitation light source with said dispersion compensating fiber.

7. The optical transmission system according to claim 6 , wherein said third optical fiber comprises a dispersion shifted fiber zero-dispersion wavelength of which is shifted to 1560 nm or less.

8. The dispersion compensating fiber according to claim 2 , further comprising an intermediate cladding region provided between said inside cladding region and said outside cladding region, said intermediate cladding region having a higher refractive index than said outside cladding region and a lower refractive index than said core region,
wherein a relative refractive index difference between said outside cladding region and a portion having a maximum refractive index in said intermediate cladding region is not less than 0.2% and not more than 0.5%.

9. An optical transmission system comprising the dispersion compensating fiber according to claim 1 and a first optical fiber optically connected with said dispersion compensating fiber and forming a part of a transmission line, said optical transmission system having the total dispersion slope not less than −0.02 ps/km/nm 2 and not more than 0.05 ps/km/nm 2 for light in the 1.5 μm-wavelength band.

10. The optical transmission system according to claim 9 , wherein said first optical fiber comprises a dispersion shifted fiber zero-dispersion wavelength of which is shifted to 1560 nm or less.

11. The optical transmission system according to claim 9 , further comprising an optical fiber amplifier forming a part of said transmission line, said optical fiber amplifier comprising:
a second optical fiber a core region of which is doped with the erbium element;
an excitation light source for outputting exciting light for exciting the erbium element in said second optical fiber, to said second optical fiber; and
an optical coupler for optically coupling said excitation light source with said second optical fiber.

12. A dispersion compensating fiber having the following characteristics for light in the 1.55 μm wavelength band:
chromatic dispersion not less than −20 ps/km/nm and not more than −5 ps/km/nm;
dispersion slope not less than −0.4 ps/km/nm 2 and not more than −0.13 ps/km/nm 2 ;
transmission loss not more than 0.5 dB/km;
polarization mode dispersion not more than 0.7 ps.km −½ ;
mode field diameter not less than 4.5 μm and not more than 6.5 μm;
cut-off wavelength not less than 0.7 μm and not more than 1.7 μm in the length of 2 m; and
bending loss at the diameter of 20 mm, not more than 100 dB/m.

13. The dispersion compensating fiber according to claim 12 , said dispersion compensating fiber being a silica-based glass fiber, comprising at least:
a core region having a predetermined refractive index, said core region having an outer diameter not less than 3.5 μm and not more than 6.0 μm;
an inside cladding region provided on the periphery of said core region and having a lower refractive index than said core region, wherein a ratio of the outer diameter of said core region to an outer diameter of said inside cladding region is not less than 0.3 and not more than 0.5; and
an outside cladding region provided on the periphery of said inside cladding region and having a higher refractive index than said inside cladding region and a lower refractive index than said core region,
wherein a relative refractive index difference between said outside cladding region and a portion having a maximum refractive index in said core region is not less than 0.6% and not more than 1.4% and wherein a relative refractive index difference between said outside cladding region and a portion having a minimum refractive index in said inside cladding region is not less than 0.25% and not more than 0.65%.

14. The dispersion compensating fiber according to claim 13 , wherein said core region is doped with the germanium element and said inside cladding region is doped with the fluorine element.

15. The dispersion compensating fiber according to claim 14 , wherein said outside cladding region is doped with the fluorine element.

16. An optical transmission system having the total dispersion slope not less than −0.02 ps/km/nm 2 and not more than 0.05 ps/km/nm 2 for light in the 1.5 μm wavelength band, said optical transmission system comprising:
the dispersion compensating fiber according to claim 15 ;
a third optical fiber optically connected with said dispersion compensating fiber and forming a part of a transmission line;
an excitation light source for outputting exciting light for exciting the erbium element in said dispersion compensating fiber to said dispersion compensating fiber; and
an optical coupler for optically coupling said excitation light source with said dispersion compensating fiber.

17. The optical transmission system according to claim 16 , wherein said third optical fiber comprises a dispersion shifted fiber zero-dispersion wavelength of which is shifted to 1560 nm or less.

18. The dispersion compensating fiber according to claim 13 , wherein said core region is doped with the erbium element.

19. The dispersion compensating fiber according to claim 13 , further comprising an intermediate cladding region provided between said inside cladding region and said outside cladding region, said intermediate cladding region having a higher refractive index than said outside cladding region and a lower refractive index than said core region,
wherein a relative refractive index difference between said outside cladding region and a portion having a maximum refractive index in said intermediate cladding region is not less than 0.2% and not more than 0.5%.

20. An optical transmission system comprising the dispersion compensating fiber according to claim 12 and a first optical fiber optically connected with said dispersion compensating fiber and forming a part of a transmission line, said optical transmission system having the total dispersion slope not less than −0.02 ps/km/nm 2 and not more than 0.05 ps/km/nm 2 for light in the 1.5 μm wavelength band.

21. The optical transmission system according to claim 20 , wherein said first optical fiber comprises a dispersion shifted fiber zero-dispersion wavelength of which is shifted to 1560 nm or less.

22. The optical transmission system according to claim 20 , further comprising an optical fiber amplifier forming a part of said transmission line, said optical fiber amplifier comprising:
a second optical fiber a core region of which is doped with the erbium element;
an excitation light source for outputting exciting light for exciting the erbium element in said second optical fiber, to said second optical fiber; and
an optical coupler for optically coupling said excitation light source with said second optical fiber.

23. A dispersion compensating fiber having the following characteristics for light in the 1 . 55 μm wavelength band:

chromatic dispersion not less than − 40 ps/km/nm and not more than 0 ps/km/nm;

dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 . 7 μm in the length of 2 m; and

bending loss at a diameter of 20 mm, not more than 100 dB/m.

24. The dispersion compensating fiber according to claim 23 , said dispersion compensating fiber being a silica- based glass fiber, comprising at least:

a core region having a predetermined refractive index, said core region having an outer diameter not less than 3 . 5 μm and not more than 6 . 0 μm;

an inside cladding region provided on the periphery of said core region and having a lower refractive index than said core region, wherein a ratio of the outer diameter of said core region to an outer diameter of said inside cladding region is not less than 0 . 3 and not more than 0 . 5 ; and

an outside cladding region provided on the periphery of said inside cladding region and having a higher refractive index than said inside cladding region and a lower refractive index than said core region,

wherein a relative refractive index difference between said outside cladding region and a portion having a maximum refractive index in said core region is not less than 0 . 6 % and not more than 1 . 4 % , and
wherein a relative refractive index difference between said outside cladding region and a portion having a minimum refractive index in said inside cladding region is not less than 0 . 25 % and not more than 0 . 65 % .

25. The dispersion compensating fiber according to claim 24 , wherein said core region is doped with germanium and said inside cladding region is doped with fluorine.

26. The dispersion compensating fiber according to claim 25 , wherein said outside cladding region is doped with fluorine.

27. The dispersion compensating fiber according to claim 24 , further comprising an intermediate cladding region provided between said inside cladding region and said outside cladding region, said intermediate cladding region having a higher refractive index than said outside cladding region and a lower refractive index than said core region,
wherein a relative refractive index difference between said outside cladding region and a portion having a maximum refractive index in said intermediate cladding region is not less than 0 . 2 % and not more than 0 . 5 % .

28. The dispersion compensating fiber according to claim 24 , wherein said core region is doped with erbium.

29. A dispersion compensating fiber having the following characteristics for light in the 1 . 55 μm wavelength band:
dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;

cutoff wavelength not less than 0 . 7 μm and not more than 1 . 7 μm at a length of 2 m and

bending loss at a diameter of 20 mm, not more than 100 dB/m.

30. The dispersion compensating fiber according to claim 29 , said dispersion compensating fiber being a silica- based glass fiber, comprising at least;

a core region having a predetermined refractive index, said core region having an outer diameter not less than 3 . 5 μm and not more than 6 . 0 μm;

31. The dispersion compensating fiber according to claim 30 , further comprising an intermediate cladding region provided between said inside cladding region and said outside cladding region, said intermediate cladding region having a higher refractive index than said outside cladding region and a lower refractive index than said core region,
wherein a relative refractive index difference between said outside cladding region and a portion having a maximum refractive index in said intermediate cladding region is not less than 0 . 2 % and not more than 0 . 5 % .

32. The dispersion compensating fiber according to claim 30 , wherein said core region is doped with germanium and said inside cladding region is doped with fluorine.

33. The dispersion compensating fiber according to claim 30 , wherein said outside cladding region is doped with fluorine.

34. The dispersion compensating fiber according to claim 30 , wherein said core region is doped with erbium.

35. An optical transmission system comprising:

a dispersion shifted fiber having a zero dispersion wavelength between the wavelengths from 1450 nm to 1650 nm; and

a dispersion compensating fiber optically coupled to said dispersion shifted fiber,

said optical transmission system having the total dispersion slope not less than − 0 . 02 ps/km/nm
2
and not more than 0 . 05 ps/km/nm
2
for light in the 1 . 55 μm wavelength band.

36. An optical transmission system according to claim 35 , further comprising:

37. An optical transmission system according to claim 36 , wherein said excitation light has a wavelength different from the wavelength of signal light to be transmitted in said dispersion compensating fiber.

38. An optical transmission system according to claim 36 , wherein said excitation light has a wavelength different from the wavelength of signal light to be transmitted in said dispersion compensating fiber.

39. An optical transmission system comprising:

an optical fiber having a positive dispersion and a positive dispersion slope at signal light having a 1 . 55 μm wavelength;

a dispersion compensating optical fiber optically coupled to said optical fiber and which compensate for the dispersion and a dispersion slope of said optical fiber at the same time; and

said optical transmission system having the total dispersion slope not less than − 0 . 02 ps/km/nm
2
and not more than 0 . 05 ps/km/nm
2
for light in the 1 . 55 μm wavelength band.

40. An optical transmission system according to claim 39 , wherein said excitation light has a wavelength different from the wavelength of signal light to be transmitted in said dispersion compensating fiber.

41. An optical transmission system comprising:

an optical fiber having a positive dispersion at signal light having a 1 . 55 μm wavelength;

a dispersion compensating optical fiber optically coupled to said optical fiber and which compensate for the dispersion and a dispersion slope of said optical fiber at the same time; and

said optical transmission system having the total dispersion slope not less than − 0 . 02 ps/km/nm
2
and not more than 0 . 05 ps/km/nm
2
for light in the 1 . 55 μm wavelength band.

42. An optical transmission system according to claim 41 , wherein said excitation light has a wavelength different from the wavelength of signal light to be transmitted in said dispersion compensating fiber.

43. A dispersion compensating optical fiber to be connected to a fiber having at least one of a positive dispersion and a positive dispersion slope at signal light having a wavelength in the 1 . 55 μm wavelength band and in which transmission loss in signal light is compensated by Raman amplification generated in said dispersion compensating optical fiber by insertion of an excitation light having a predetermined wavelength, said dispersion compensating optical fiber having the following characteristics for light in the 1 . 55 μm wavelength band;
dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 . 7 μm in the length of 2 m; and

bending loss at the diameter of 20 mm, not more than 100 dB/m,

whereby, when said dispersion compensating optical fiber is connected to said dispersion shifted fiber, an optical transmission system consisting of said fiber and said dispersion compensating optical fiber has the total dispersion slope not less than − 0 . 02 ps/km/nm
2
and not more than 0 . 05 ps/km/nm
2
for light in the 1 . 55 μm wavelength band.

44. A dispersion compensating optical fiber to be connected to a dispersion shifted fiber having a zero dispersion wavelength between the wavelengths from 1450 nm to 1650 nm, said dispersion compensating optical fiber having the following characteristics for light in the 1 . 55 μm wavelength band;
dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 . 7 μm in the length of 2 m; and

bending loss at a diameter of 20 mm, not more than 100 dB/m,

whereby, when said dispersion compensating optical fiber is connected to said dispersion shifted fiber and an excitation light having a predetermined wavelength is inserted into said dispersion compensating optical fiber, the loss in the signal light in an optical transmission system consisting of said dispersion shifted fiber and said dispersion compensating optical fiber is compensated by the Raman amplification generated by the insertion of the excitation light so that said optical transmission system has the total dispersion slope not less than − 0 . 02 ps/km/nm
2
and not more than 0 . 05 ps/km/nm
2
for light in the 1 . 55 μm wavelength band.

45. A dispersion compensating optical fiber to be connected to a dispersion shifted fiber having a zero dispersion wavelength between the wavelengths from 1450 nm to 1650 nm, said dispersion compensating fiber having the following characteristics for light in the 1 . 55 μm wavelength band:

chromatic dispersion not less than − 40 ps/km/nm and not more than 0 ps/km/nm;

dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 7 μm in the length of 2 m; and

bending loss at the diameter of 20 mm, not more than 100 dB/m,

46. A dispersion compensating optical fiber to be connected to a dispersion shifted fiber having at least one of a positive dispersion and a positive dispersion slope at signal light having the wavelength of 1 . 55 μm wavelength band, said dispersion compensating fiber having the following characteristics for light in the 1 . 55 μm wavelength band:

chromatic dispersion not less than − 40 ps/km/nm and not more than 0 ps/km/nm;

dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 . 7 μm in the length of 2 m; and

bending loss at a diameter of 20 mm, not more than 100 dB/m,

47. An optical transmission system said optical transmission system comprising:

an optical fiber having a zero dispersion wavelength between the wavelengths from 1450 nm to 1650 nm;

a dispersion compensating fiber optically coupled to said optical fiber and having the following characteristics for light in the 1 . 55 μm wavelength band;

dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 . 7 μm in the length of 2 m; and

bending loss at a diameter of 20 mm, not more than 100 dB/m; and

a light source coupled with said dispersion compensating fiber and for generating an excitation light into said dispersion compensating fiber to amplify a signal light in said dispersion compensating fiber by utilizing a Raman amplification, thereby to compensate loss in signal light to be transmitted in said dispersion compensating fiber, which is caused in said dispersion compensating fiber, said optical transmission system having the total dispersion slope not less than − 0 . 02 ps/km/nm
2
and not more than 0 . 05 ps/km/nm
2
for light in the 1 . 55 μm wavelength band.

48. An optical transmission system comprising:

an optical fiber having at least one of a positive dispersion and a positive dispersion slope at signal light having a 1 . 55 μm wavelength;

a dispersion compensating fiber optically coupled to said optical fiber and having the following characteristics for light in the 1 . 55 μm wavelength band;

dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 . 7 μm in the length of 2 m; and

bending loss at a diameter of 20 mm, not more than 100 dB/m; and

49. An optical transmission system comprising:

an optical fiber having at least one of a positive dispersion and a positive dispersion slope at signal light having a 1 . 55 μm wavelength;

a dispersion compensating fiber optically coupled to said optical fiber and having the following characteristics for light in the 1 . 55 μm wavelength band;

chromatic dispersion not less than − 40 ps/km/nm and not more than 0 ps/km/nm;

dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 . 7 μm in the length of 2 m; and

bending loss at a diameter of 20 mm, not more than 100 dB/m; and

50. An optical transmission system comprising:

a dispersion shifted fiber having a zero dispersion wavelength between the wavelengths from 1450 nm to 1650 nm a dispersion shifted fiber having a zero dispersion wavelength between the wavelengths from 1450 nm to 1650 nm wavelength;

a dispersion compensating fiber optically coupled to said optical fiber and having the following characteristics for light in the 1 . 55 μm wavelength band;

chromatic dispersion not less than − 40 ps/km/nm and not more than 0 ps/km/nm;

dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 . 7 μm in the length of 2 m; and

bending loss at a diameter of 20 mm, not more than 100 dB/m; and

a light source coupled with said dispersion compensating fiber and for generating an excitation light into said dispersion compensating fiber to amplify a signal light in said dispersion compensating fiber by utilizing a Raman amplification thereby to compensate loss in signal light to be transmitted in said dispersion compensating fiber, which is caused in said dispersion compensating fiber, and said optical transmission system having the total dispersion slope not less than − 0 . 02 ps/km/nm
2
and not more than 0 . 05 ps/km/nm
2
for light in the 1 . 55 μm wavelength band.

51. A dispersion compensating optical fibre to be connected to a dispersion shifted fiber having at least one fo a positive dispertion and a positive dispersion slope at signal light having a wavelength of 1 . 55 μm wavelength band, said dispersion compensating fiber having the following characteristics for light in the 1 . 55 μm wavelength band:
dispersion slope not less than − 0 . 5 ps/km/nm 2 and not more than − 0 . 1 ps/km/nm 2 ;

transmission loss not more than 0 . 5 dB/km;

polarization mode dispersion not more than 0 . 7 ps·km −½ ;
cut - off wavelength not less than 0 . 7 μm and not more than 1 . 7 μm in the length of 2 m; and

bending loss at the diameter of 20 mm not more than 100 dB/m,

whereby, when said dispersion compensating optical fiber is connected to said dispersion shifted fiber and an excitation light having a predetermined wavelength is inserted inot said dispersion compensating optical fiber, the loss in the signal light in an optical transmission system consisting of said dispersion shifted fiber and said dispersion compensating optical fiber is compensated by the Raman amplification generated by the insertion of the excitation light so that said optical transmission system has a total dispersion slope not less than − 0 . 02 ps/km/nm
2
and not more than 0 . 05 ps/km/nm
2
for light in the 1 . 55 μm wavelength band.

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