Multimode optical fiber with low bending losses and reduced cladding effect

• US 8,406,593 B2
• Filed: 12/03/2010
• Issued: 03/26/2013
• Est. Priority Date: 12/03/2009
• Status: Active Grant

• Current Assignee: Draka Comteq BV (Prysmian SPA)
• Original Assignee: Draka Comteq BV (Prysmian SPA)
• Inventors: Molin, Denis, Bigot-Astruc, Marianne, Sillard, Pierre, de Jongh, Koen
• Primary Examiner(s): Robinson, Mark
• Assistant Examiner(s): Jordan, Andrew
• Application Number:
  US12/959,688
• Publication Number:
  US 20110135262A1
• Time in Patent Office: 844 Days
• Field of Search: 385/124
• US Class Current: 385/124
• CPC Class Codes: G02B 6/0288 Multimode fibre, e.g. graded index core for compensating modal dispersion
• CPC Class Codes: G02B 6/03627 arranged - +
• CPC Class Codes: G02B 6/0365 arranged - - +

Abstract

The present invention embraces an optical fiber that includes a central core having an alpha-index profile with respect to an outer cladding. The optical fiber also includes an inner cladding, a depressed trench, and an outer cladding. Typically, the alpha-index profile of the central core is interrupted at a point having a positive refractive index difference with respect to the outer cladding. The optical fiber achieves reduced bending losses and a high bandwidth with a reduced cladding effect for high-data-rate applications.

Claims

1. A multimode optical fiber, comprising:

a central core surrounded by an outer cladding, said central core having (i) an outer radius r₁, (ii) a minimum refractive index difference Δ

n_end with respect to said outer cladding that is greater than 0, and (iii) an alpha-index profile with respect to said outer cladding, the alpha-index profile being interrupted at said central core'"'"'s outer radius r₁, the alpha-index profile defining a theoretical radius r_1zero;

an inner cladding positioned between said central core and said outer cladding, said inner cladding having (i) an outer radius r₂, (ii) a width w₂, and (iii) a refractive index difference Δ

n₂ with respect to said outer cladding; and

a depressed trench positioned between said inner cladding and said outer cladding, said depressed trench having (i) an outer radius r_out, (ii) a width w₃, and (iii) a refractive index difference Δ

n₃ with respect to said outer cladding;

wherein the difference between said inner cladding'"'"'s outer radius r₂ and the alpha-index profile'"'"'s theoretical radius r_1zero is greater than about 0.5 micron and less than 2 microns;

wherein said inner cladding'"'"'s refractive index difference Δ

n₂ and said depressed trench'"'"'s refractive index difference Δ

n₃ satisfy the following inequalities;

−

11.9×

(1000Δ

n₂)²−

3.4×

(1000Δ

n₂)−

7.2<

1000Δ

n₃; and

1000Δ

n₃<

−

17.2×

(1000Δ

n₂)²+16.5×

(1000Δ

n₂)−

8.0.

2. A multimode optical fiber according to claim 1, wherein said central core'"'"'s alpha-index profile has an alpha parameter α

of between about 1.9 and 2.1.

3. A multimode optical fiber according to claim 1, wherein said central core'"'"'s alpha-index profile has an alpha parameter α

of between 2.0 and 2.1.

4. A multimode optical fiber according to claim 1, wherein, with respect to said outer cladding, said central core has a maximum refractive index difference Δ

n₁ of between about 11×

10<sup>−

3</sup> and 16×

10<sup>−

3</sup>.

5. A multimode optical fiber according to claim 1, wherein the alpha-index profile'"'"'s theoretical radius r_1zero is between about 23 microns and 27 microns.

6. A multimode optical fiber according to claim 1, wherein said inner cladding immediately surrounds said central core and said depressed trench immediately surrounds said inner cladding.

7. A multimode optical fiber according to claim 1, wherein said central core'"'"'s minimum refractive index difference Δ

n_end is such that Δ

n_end=Δ

n₂±

0.1×

10<sup>−

3</sup>.

8. A multimode optical fiber according to claim 1, wherein said inner cladding'"'"'s refractive index difference Δ

n₂ is between about 0.2×

10<sup>−

3</sup> and 2×

10<sup>−

3</sup>.

9. A multimode optical fiber according to claim 1, wherein said depressed trench'"'"'s outer radius r_out is less than about 32 microns.

10. A multimode optical fiber according to claim 1, wherein said depressed trench'"'"'s refractive index difference Δ

n₃ is between about −

15×

10<sup>−

3</sup> and −

3×

10<sup>−

3</sup>.

11. A multimode optical fiber according to claim 1, wherein said depressed trench'"'"'s width w₃ is between about 3 microns and 6 microns.

12. A multimode optical fiber according to claim 1, wherein said depressed trench has a volume v₃ of between about 200%·

μ

m² and 1,200%·

μ

m².

13. A multimode optical fiber according to claim 1, wherein the difference between said inner cladding'"'"'s outer radius r₂ and the alpha-index profile'"'"'s theoretical radius r_1zero is less than about 1.5 microns.

14. A multimode optical fiber according to claim 1, wherein said inner cladding'"'"'s refractive index difference Δ

n₂ and said depressed trench'"'"'s refractive index difference Δ

n₃ satisfy the following inequality;

−

13.6×

(1000Δ

n₂)²−

5.2<

1000Δ

n₃<

−

18.1×

(1000Δ

n₂)²+13.5×

(1000Δ

n₂)−

7.

15. A multimode optical fiber according to claim 1, wherein, for two turns around a bend radius of 15 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of less than about 0.1 dB.

16. A multimode optical fiber according to claim 1, wherein, for two turns around a bend radius of 10 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of less than about 0.1 dB.

17. A multimode optical fiber according to claim 1, wherein, for two turns around a bend radius of 7.5 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of less than about 0.2 dB.

18. A multimode optical fiber according to claim 1, wherein, for two turns around a bend radius of 7.5 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of less than about 0.01 dB.

19. A multimode optical fiber according to claim 1, wherein, for two turns around a bend radius of 5 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of less than about 0.3 dB.

20. A multimode optical fiber according to claim 1, wherein, for a half turn around a bend radius of 5.5 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of about 0.1 dB or less.

21. A multimode optical fiber according to claim 1, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an OFL bandwidth of at least about 1,500 MHz·

km.

22. A multimode optical fiber according to claim 1, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an OFL bandwidth of at least about 3,500 MHz·

km.

23. A multimode optical fiber according to claim 1, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an OFL bandwidth of at least about 8,000 MHz·

km.

24. A multimode optical fiber according to claim 1, wherein the multimode optical fiber has a numerical aperture of 0.2±

0.015.

25. A multimode optical fiber according to claim 1, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an outer DMD value of less than about 0.33 ps/m.

26. A multimode optical fiber according to claim 1, wherein:

said central core'"'"'s outer radius r₁ is between about 23.5 microns and 26.5 microns; and

at a wavelength of 850 nanometers, the multimode optical fiber has an outer DMD value (0-23 microns) of less than about 0.1 ps/m.

27. An optical-fiber system comprising at least a portion of the multimode optical fiber according to claim 1.

28. An optical-fiber system according to claim 27, wherein the optical-fiber system has a data rate of at least about 10 Gb/s over a distance of about 100 meters.

29. A multimode optical fiber, comprising:

a central core surrounded by an outer cladding, said central core having (i) an outer radius r₁, (ii) a maximum refractive index difference Δ

n₁ of between about 11×

10<sup>−

3</sup> and 16×

10<sup>−

3</sup>, (iii) a minimum refractive index difference Δ

n_end with respect to said outer cladding that is greater than 0, and (iv) an alpha-index profile with respect to said outer cladding, the alpha-index profile being interrupted at said central core'"'"'s outer radius r₂, the alpha-index profile defining a theoretical radius r_1zero;

an inner cladding positioned between said central core and said outer cladding, said inner cladding having (i) an outer radius r₂, (ii) a width w₂, and (iii) a refractive index difference Δ

n₂ with respect to said outer cladding of between about 0.2×

10<sup>−

3</sup> and 2×

10<sup>−

3</sup>; and

a depressed trench positioned between said inner cladding and said outer cladding, said depressed trench having (i) an outer radius r_out, (ii) a width w₃, and (iii) a refractive index difference Δ

n₃ with respect to said outer cladding of between about −

15×

10<sup>−

3</sup> and −

3×

10<sup>−

3</sup>;

wherein the difference between said inner cladding'"'"'s outer radius r₂ and the alpha-index profile'"'"'s theoretical radius r_1zero is greater than about 0.5 micron and less than 2 microns;

wherein said inner cladding'"'"'s refractive index difference Δ

n₂ and said depressed trench'"'"'s refractive index difference Δ

n₃ satisfy the following inequalities;

−

11.9×

(1000Δ

n₂)²−

3.4×

(1000Δ

n₂)−

7.2<

1000Δ

n₃; and

1000Δ

n₃<

−

17.2×

(1000Δ

n₂)²+16.5×

(1000Δ

n₂)−

8.0.

30. A multimode optical fiber according to claim 29, wherein said depressed trench'"'"'s outer radius r_out is less than about 30 microns.

31. A multimode optical fiber according to claim 29, wherein, for two turns around a bend radius of 15 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of less than about 0.05 dB.

32. A multimode optical fiber according to claim 29, wherein, for two turns around a bend radius of 5 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of less than about 1 dB.

33. A multimode optical fiber according to claim 29, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an OFL bandwidth of at least about 10,000 MHz·

km.

34. A multimode optical fiber, comprising:

a central core surrounded by an outer cladding, said central core having (i) an outer radius r₂, (ii) a minimum refractive index difference Δ

n_end with respect to said outer cladding that is greater than 0, and (iii) an alpha-index profile with respect to said outer cladding, the alpha-index profile being interrupted at said central core'"'"'s outer radius r₁, the alpha-index profile defining a theoretical radius r_1zero;

an inner cladding positioned between said central core and said outer cladding, said inner cladding having (i) an outer radius r₂, (ii) a width w₂, and (iii) a refractive index difference Δ

n₂ with respect to said outer cladding; and

a depressed trench positioned between said inner cladding and said outer cladding, said depressed trench having (i) an outer radius r_out of less than about 32 microns, (ii) a width w₃, and (iii) a refractive index difference Δ

n₃ with respect to said outer cladding;

wherein the difference between said inner cladding'"'"'s outer radius r₂ and the alpha-index profile'"'"'s theoretical radius r_1zero is greater than about 0.5 micron and less than about 1.5 microns;

wherein said inner cladding'"'"'s refractive index difference Δ

n₂ and said depressed trench'"'"'s refractive index difference Δ

n₃ satisfy the following inequalities;

−

11.9×

(1000Δ

n₂)²−

3.4×

(1000Δ

n₂)−

7.2<

1000Δ

n₃; and

1000Δ

n₃<

−

17.2×

(1000Δ

n₂)²+16.5×

(1000Δ

n₂)−

8.0.

35. A multimode optical fiber according to claim 34, wherein said depressed trench has a volume v₃ of between about 250%·

μ

m² and 750%·

μ

m².

36. A multimode optical fiber according to claim 34, wherein, for two turns around a bend radius of 10 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of less than about 0.3 dB.

37. A multimode optical fiber according to claim 34, wherein, for two turns around a bend radius of 7.5 millimeters at a wavelength of 850 nanometers, the multimode optical fiber has bending losses of less than about 0.1 dB.

38. A multimode optical fiber according to claim 34, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an OFL bandwidth of at least about 6,000 MHz·

km.

39. A multimode optical fiber according to claim 34, wherein:

said central core'"'"'s outer radius r₁ is 25±

1.5 microns; and

at a wavelength of 850 nanometers, the multimode optical fiber has an outer DMD value (0-23 microns) of less than about 0.25 ps/m.