Large core holey fibers

• US 10,197,727 B2
• Filed: 04/11/2017
• Issued: 02/05/2019
• Est. Priority Date: 01/16/2004
• Status: Active Grant

• 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): Mooney, Michael
• Application Number:
  US15/485,025
• Publication Number:
  US 20170343731A1
• Time in Patent Office: 665 Days
• Field of Search: 385123-124, 385126-128, 3593411, 3593413
• 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

Holey fibers provide optical propagation. In various embodiments, 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 spacing to yield a desired operation with a desired leakage loss of the fundamental mode. Resulting holey 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.

Claims

1. An optical fiber for propagating a fundamental mode of said optical fiber, said optical fiber comprising:

a cladding region comprising a plurality of cladding features disposed in a matrix, said plurality of cladding features having an average spacing, A, and an average size, d, said plurality of cladding features being substantially arranged in a plurality of rows, N; and

a core region surrounded by said cladding region, wherein said core region is formed in an area where a center hole and at least a first layer of holes would otherwise be located in the matrix, wherein an effective core size of said core region is at least about 30 micrometers and less than about 150 micrometers,

wherein said optical fiber is configured to propagate the fundamental mode substantially in the fundamental mode for the length of the fiber.

2. The optical fiber of claim 1, wherein said core region is formed in the area where the center hole and the first row of holes would otherwise be located in the matrix.

3. The optical fiber of claim 1, wherein said core region is formed in the area where the center hole and the first and second rows of holes would otherwise be located in the matrix.

4. The optical fiber of claim 1, wherein the optical fiber is configured to propagate the fundamental mode at a wavelength, λ

, and λ

/Λ

is less than or equal to about 0.3.

5. The optical fiber of claim 1, wherein said cladding features comprise a material that is a gas, a mixture of gases, or a glass.

6. The optical fiber of claim 1, wherein said core region has a refractive index that is uniform to within about 0.001 as measured across a lateral cross-section that is perpendicular to a longitudinal direction of the fiber length.

7. The optical fiber of claim 1, wherein a V number of the optical fiber is greater than about 2.4.

8. The optical fiber of claim 1, further comprising dopants that provide gain.

9. The optical fiber of claim 1, wherein said core region comprises a doped region, said optical fiber further comprising an outer cladding having a plurality of holes.

10. The optical fiber of claim 1, wherein said cladding region includes a first and second set of cladding features, said first set of cladding features arranged to support propagation of at least the fundamental mode and said second set of cladding features arranged to support propagation of multiple modes for pump propagation.

11. A cladding pumped fiber amplifier or cladding pumped fiber laser, comprising:

the optical fiber of claim 1; and

a pump source optically connected to said optical fiber.

12. The optical fiber of claim 1, wherein said plurality of cladding features are asymmetric.

13. The optical fiber of claim 12, wherein said plurality of cladding features have two-fold symmetry so as to maintain polarization of light propagating through said core region.

14. The optical fiber 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 first or second material comprising a gas, a mixture of gases, or a glass.

15. The optical fiber of claim 1, wherein said plurality of cladding features include a first plurality of larger size features separated from each other by a distance, s1, and a second plurality of smaller size features separated from each other by a distance s2.

16. The optical fiber of claim 15, wherein said distance, s1 is approximately equal to said distance s2.

17. The optical fiber of claim 1, wherein said average size, d, said average spacing, Λ

, and said plurality of rows N have values that provide a leakage loss for said fundamental mode that is below about 1 dB and a leakage loss for higher order modes that is above about 20 dB.

18. The optical fiber of claim 1, further comprising at least one mode filter configured to suppress higher order modes by introducing substantially greater loss to said higher order modes than to said fundamental mode, such that said fundamental mode dominates while said higher order modes are quenched.

19. The optical fiber of claim 18, wherein said at least one mode filter comprises a filter selected from the group consisting of a bent optical fiber, an optical fiber with gain profiling, an optical fiber with loss profiling, and a tapered fiber.