Barbell optical fiber and method of making the same

Patent metadata

Field	Value
Publication number	US-9322988-B2
Application number	US-201314395698-A
Country	US
Kind code	B2
Filing date	May 13, 2013
Priority date	May 11, 2012
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

High aspect ratio core optical fiber designs, which could be semi-guiding, including a core region having a first refractive index and a high aspect ratio elongated cross-section along a slow axis direction, are described. An internal cladding having a second refractive index sandwiches the core and acts as a fast-axis signal cladding. The core has an edge region at both of its short edges that is in contract with edge-cladding regions having a barbell shape. The refractive index of the core regions, the refractive index of the internal claddings, and the refractive index of the edge-cladding regions, are selected so as to maximize the optical power of a lowest-order mode propagating in the fiber core, and to minimize the optical power of the next-order modes in the fiber core. A process to fabricate such a high aspect ratio core fiber is also provided.

First claim

What is claimed is:

1. A method of making a high aspect ratio core optical fiber preform, comprising:
forming a near-net rectangular shape core region of a first composition and having an elongated cross-section with a wide slow-axis dimension and a narrow fast-axis direction;
forming a pair of near-net shape cladding elements having a second composition;
disposing the pair of near-net shape cladding elements adjacent to each slow-axis edge of the core region to form a pair of edge-cladding regions, the combination exhibiting a barbell configuration; and
surrounding the combination of the near-net rectangular shape core region and the pair of near-net shape cladding elements with an outer cladding of a third composition.

2. The method of claim 1 wherein the second composition is different from the first composition.

3. The method of claim 1 wherein the second composition is the same as the first composition, forming a semi-guiding high aspect ratio core optical fiber preform.

4. The method of claim 1 wherein at least one of the pair of near-net shape cladding elements comprises a solid rod.

5. The method of claim 1 wherein at least one of the pair of near-net shape cladding elements comprises an array of rods.

6. The method of claim 1 wherein one or more of the near-net shapes are formed by one or more of the processing techniques including: sol-gel processing, outside vapor deposition (OVD), inside vapor deposition (IVD), vapor axial deposition (VAD), planar soot deposition (PSD), and combinations thereof.

7. The method of claim 1 wherein the composition of one or more of the near-net shapes may be achieved through a doping process comprising one or more of sol-gel doping, molecular stuffing, solution doping and vapor doping.

8. A fiber formed in accordance with the method of claim 1 by drawing down the high aspect ratio core optical fiber preform.

9. A method of making a high aspect ratio core optical fiber preform comprising:
providing an outer mold;
inserting an inner mold within an opening in the outer mold, the inner mold exhibiting a barbell configuration including a near-net rectangular shape having an elongated cross-section with a wide slow axis dimension and a narrow fast axis direction with a pair of near-net shapes adjacent to each fast axis edge of the near-net rectangular shape;
placing cladding material of a first composition in open areas between the outer mold and the inner mold;
removing the inner mold;
inserting a near-net rectangular shape core region of a second composition, and having an elongated cross-section with a wide slow axis dimension and a narrow fast axis direction, in the opening created by removing the inner mold; and
inserting a pair of near-net shape elements having a third composition at opposing end terminations of the slow-axis edges of the near-net rectangular shape core region, forming a pair of edge-cladding regions.

10. The method of claim 9 wherein the step of inserting a pair of near-net shape elements includes the step of inserting a pair of rods.

11. The method of claim 10 wherein the pair of rods comprise a pair of fused-silica rods.

12. The method as defined in claim 10 wherein the pair of rods exhibit a cross-section shape selected from the group consisting of: circular, elliptical and rectangular.

13. The method of claim 9 wherein the step of inserting a pair of near-net shape elements consists of:
disposing porous glass in open areas between the cladding material and the near-net rectangular core region; and
consolidating the porous glass to form a pair of edge-cladding regions.

14. The method of claim 9 wherein the step of inserting a pair of near-net shape elements consists of:
disposing silica granules in open areas between the cladding material and the near-net rectangular core region; and
consolidating the silica granules to form a pair of edge-cladding regions.

15. An optical fiber made according to the method of claim 9 by drawing down the high aspect ratio core optical fiber preform.

16. A method of making a high aspect ratio core optical fiber preform, comprising:
providing a first half of a clam shell mold structure, the first half formed of a first composition and including central longitudinal region and opposing semi-circular regions extending longitudinally along either side thereof;
disposing a near-net rectangular shape core region on the central longitudinal region, the near-net rectangular shape core region of a second composition and having an elongated cross-section with a wide slow axis dimension and a narrow fast axis direction;
disposing a pair of near-net shape cladding elements of a third composition within each semi-circular region such that the near-net shape cladding elements contacts the near-net rectangular shape core region; and
covering with a second half of the clam shell mold structure, the second half of the clam shell mold formed of the first composition and including semi-circular regions for encasing the pair of near-net shape cladding elements, the combination of the first and second halves of the clam shell mold forming a cladding region for the high aspect ratio core optical fiber preform.

17. An optical fiber formed in accordance with the method of claim 16 by drawing down the high aspect ratio core optical fiber preform.

18. A high aspect ratio core optical fiber exhibiting a barbell configuration comprising:
a near-net rectangular shape core region of a first composition, the core region having an elongated cross-section with a wide slow axis dimension and a narrow fast axis direction;
a pair of near-net shape cladding regions having a second composition, the pair of near-net shape cladding regions disposed adjacent to each fast axis edge of the core so as to contact the edges of the core region, the combination exhibiting a barbell configuration; and
an outer cladding of a third composition disposed to surround the barbell configuration, the third composition being different from the first composition.

19. A high aspect ratio core optical fiber as defined in claim 18 wherein the near-net rectangular core region comprises silica.

20. A high aspect ratio core optical fiber as defined in claim 19 wherein at least a central portion of the core region is doped.

21. A high aspect ratio core optical fiber as defined in claim 19 wherein the core region is doped with an optical gain material selected from the group consisting of: Er, Yb, Tm.

22. A high aspect ratio core optical fiber as defined in claim 21 wherein the edge-cladding regions comprise a pair of glass rods.

23. A barbell-structure optical fiber, comprising:
a high aspect ratio core region having an elongated cross-section with a wide slow-axis dimension and a narrow fast-axis dimension, wherein the core region has a substantially rectangular shape in cross-section including a width and a height defining an aspect ratio of width to height, the core region having an aspect ratio at least 10:1, and the core region having a first refractive index;
an inner cladding region positioned in contact with and sandwiching the core region, the inner cladding having a second refractive index lower than the first refractive index;
an outer cladding region arranged to surround the inner cladding, the outer cladding region having a third refractive index lower than the second refractive index; and
a first edge-cladding region and a second edge-cladding region, the first edge-cladd

Assignees

• Ofs Fitel Llc
• Raytheon Co

Inventors

• Digiovanni David J
• Trevor Dennis J
• Rockwell David A
• Shkunov Vladimir V

Classifications

• H01S3/0672

  Non-uniform radial doping · CPC title

• H01S3/1698

  rare earth · CPC title

• H01S3/08045

  Single-mode emission · CPC title

• G02B6/028 Primary

  with core or cladding having graded refractive index {(G02B6/02033, G02B6/02295 take precedence)} · CPC title

• C03B2203/12

  Non-circular or non-elliptical cross-section, e.g. planar core · CPC title