Large core holey fibers

• US 8,285,099 B2
• Filed: 09/06/2007
• Issued: 10/09/2012
• Est. Priority Date: 01/16/2004
• Status: Expired due to Fees

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Dong, Liang, Harter, Donald J., Wong, William
• Primary Examiner(s): N Le, Uyen Chau
• Assistant Examiner(s): Mooney, Michael P
• Application Number:
  US11/851,270
• Publication Number:
  US 20080056656A1
• Time in Patent Office: 1,860 Days
• Field of Search: 385123-124, 385126-128, 359/333, 359/341.1, 359/341.3
• US Class Current: 385/125
• CPC Class Codes: G02B 6/02009 Large effective area or mode field radius, e.g. to reduce nonlinear effects in single mode fibres
• CPC Class Codes: G02B 6/02047 Dual mode fibre G02B6/105 takes precedence
• CPC Class Codes: G02B 6/02328 Hollow or gas filled core
• CPC Class Codes: G02B 6/02338 Structured core, e.g. core contains more than one material, non-constant refractive index distribution in core, asymmetric or non-circular elements in core unit, multiple cores, insertions between core and clad
• CPC Class Codes: G02B 6/02342 characterised by cladding features, i.e. light confining region
• CPC Class Codes: G02B 6/02357 Property of longitudinal structures or background material varies radially and/or azimuthally in the cladding, e.g. size, spacing, periodicity, shape, refractive index, graded index, quasiperiodic, quasicrystals
• CPC Class Codes: G02B 6/02361 Longitudinal structures forming multiple layers around the core, e.g. arranged in multiple rings with each ring having longitudinal elements at substantially the same radial distance from the core, having rotational symmetry about the fibre axis
• CPC Class Codes: G02B 6/02366 Single ring of structures, e.g. "air clad"
• CPC Class Codes: G02B 6/024 with polarisation maintaining properties
• CPC Class Codes: G02B 6/032 with non solid core or cladding G02B6/02295 takes precedence
• CPC Class Codes: G02B 6/14 Mode converters
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262
• CPC Class Codes: H01S 3/06716 Fibre compositions per se C03C13/04or doping with active elements lasing materials in general H01S3/14
• CPC Class Codes: H01S 3/06729 Peculiar transverse fibre profile
• CPC Class Codes: H01S 3/06733 Fibre having more than one cladding
• CPC Class Codes: H01S 3/06741 Photonic crystal fibre, i.e. the fibre having a photonic bandgap
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence

Abstract

Various types of holey fiber provide optical propagation. In various embodiments, for example, a large core holey fiber comprises a cladding region formed by large holes arranged in few layers. The number of layers or rows of holes about the large core can be used to coarse tune the leakage losses of the fundamental and higher modes of a signal, thereby allowing the non-fundamental modes to be substantially eliminated by leakage over a given length of fiber. Fine tuning of leakage losses can be performed by adjusting the hole dimension and/or the hole spacing to yield a desired operation with a desired leakage loss of the fundamental mode. Resulting holely fibers have a large hole dimension and spacing, and thus a large core, when compared to traditional fibers and conventional fibers that propagate a single mode. Other loss mechanisms, such as bend loss and modal spacing can be utilized for selected modes of operation of holey fibers. Other embodiments are also provided.

Claims

1. An optical fiber amplifier comprising:

an optical gain fiber for propagating a single mode, said optical gain fiber providing optical gain, said optical gain fiber comprising;

(i) a cladding region comprising a plurality of cladding features disposed in a matrix, said plurality of cladding features having an average spacing, Λ

, and an average size, d; and

(ii) a core region surrounded by said cladding region, said plurality of cladding features substantially confining propagation of said single mode to said core region, said plurality of cladding features having (i) sufficient average spacing, Λ

, to provide an increased effective core size, 2ρ

, and (ii) a sufficient average size, d, to provide substantial confinement of light within said core region,

wherein an inner portion of said cladding region defines said core region, said inner portion comprises a first plurality of said plurality of cladding features, and said average size, d, of said first plurality of cladding features is greater than about 60% of said average spacing, Λ

, of said first plurality of cladding features.

2. The optical fiber amplifier of claim 1,

wherein said average size, d, of said first plurality of cladding features is substantially equal to said average spacing, Λ

, of said plurality of cladding features.

3. The optical fiber amplifier of claim 1, further comprising a resonant cavity formed by at least partially reflective surfaces.

4. The optical fiber amplifier of claim 3, wherein said optical gain fiber is within said resonant cavity.

5. The optical fiber amplifier of claim 1, further comprising an optical pump source optically coupled to said optical gain fiber to provide pumping thereto.

6. The optical fiber amplifier of claim 5, further comprising an optical signal source optically coupled to said optical gain fiber to provide an optical signal thereto.

7. The optical fiber amplifier of claim 1, wherein said optical gain fiber comprises an outer cladding disposed about the cladding region, said outer cladding comprising a plurality of holes, such that said optical gain fiber is configured as a double clad optical gain fiber.

8. The optical fiber amplifier of claim 7, wherein said plurality of holes in said outer cladding is arranged in a hexagonal shape.

9. The optical fiber amplifier of claim 1, wherein said matrix comprises a first material having a first refractive index, and at least a portion of said cladding features comprise a second material having a second refractive index that is less than the first refractive index, said second material comprising a gas, a mixture of gases, or a glass.

10. The optical fiber amplifier of claim 1, wherein a V number of said optical gain fiber is greater than about 2.4 and up to about 10.

11. The optical fiber amplifier of claim 1, wherein said optical gain fiber supports multiple modes and is configured to propagate a single-mode input signal through said optical gain fiber, wherein said cladding region and said core region yield an effective refractive index for each of said fundamental and higher order modes, said effective refractive index of said fundamental mode and said effective refractive index of said higher order modes having a difference that is larger than about 0.001 such that mode coupling between said fundamental mode and said higher order modes is substantially reduced.

12. The optical fiber amplifier of claim 11, wherein said optical gain fiber is bent with a bending radius less than about 10 cm, and said effective refractive index of said fundamental mode and said effective refractive index of said higher order modes have a difference that is larger than about 0.005.

13. The optical fiber amplifier of claim 1, wherein said average size, d, of said first plurality of cladding features is greater than about 70% of said average spacing, Λ

, of said first plurality of cladding features.

14. The optical fiber amplifier of claim 1, wherein said average size, d, of said first plurality of cladding features is greater than about 80% of said average spacing, Λ

, of said first plurality of cladding features.

15. The optical fiber amplifier of claim 1, wherein said average size, d, of said first plurality of cladding features is greater than about 85% of said average spacing, Λ

, of said first plurality of cladding features.

16. The optical fiber amplifier of claim 1, wherein said average size, d, of said first plurality of cladding features is greater than about 90% of said average spacing, Λ

, of said first plurality of cladding features.

17. The optical fiber amplifier of claim 1, wherein said average size, d, of said first plurality of cladding features is greater than about 95% of said average spacing, Λ

, of said first plurality of cladding features.

18. The optical fiber amplifier of claim 1, wherein said first plurality of cladding features comprises one layer of cladding features.

19. The optical fiber amplifier of claim 1, wherein said plurality of cladding features comprises no more than four layers of cladding features, and said first plurality of cladding features comprises a first layer of said no more than four layers of cladding features, said f irst layer closest to said core region.

20. The optical fiber amplifier of claim 1, wherein said average size, d, of said first plurality of cladding features is at least 15 μ

m.

21. The optical fiber amplifier of claim 1, wherein said spacing, Λ

, of said first plurality of cladding features is at least 15 μ

m.

22. The optical fiber amplifier of claim 1, wherein said effective core size 2ρ

is at least 25 μ

m.

23. The optical fiber amplifier of claim 1, wherein the plurality of cladding features is affanged in a plurality of rows, N, and wherein a number of rows N is less than 4.