MULTI-CLADDING FIBER

• US 20110081123A1
• Filed: 01/17/2008
• Published: 04/07/2011
• Est. Priority Date: 01/17/2008
• Status: Active Grant

• Current Assignee: Institut national d'optique
• Original Assignee: Institut national d'optique
• Inventors: Pare, Claude, Zheng, Huimin, Laperle, Pierre, Crotrau, Andre
• Granted Patent: US 8,731,358 B2
• Time in Patent Office: Days
• US Class Current: 385/124
• CPC Class Codes: G02B 6/02023 Based on higher order modes, i.e. propagating modes other than the LP01 or HE11 fundamental mode mode converters G02B6/14
• CPC Class Codes: G02B 6/03644 arranged - + -
• CPC Class Codes: G02B 6/03661 having 4 layers only
• CPC Class Codes: H01S 3/06729 Peculiar transverse fibre profile

Abstract

Multi-cladding optical fibers to be used in the context of fiber amplifiers and fiber lasers are described herein. Embodiments of optical fibers include a rare-earth doped core into which the signal field is to be amplified. The doped core is surrounded by multiple claddings that guide the pump field to be absorbed by the reactive core material. The first cladding has a depressed refractive index to improve high-order mode bending losses without incurring significant fundamental mode bending losses.

Claims

1. A multi-cladding optical fiber including:

a longitudinal core having at least a portion thereof that is rare-earth doped;

the core having a core refractive index;

a first cladding surrounding the longitudinal core;

the first cladding having a first cladding refractive index lower than the core refractive index;

a second cladding surrounding the first cladding;

the second cladding having a second cladding refractive index higher than the first cladding refractive index; and

an external cladding surrounding the second cladding.

2. The multi-cladding optical fiber of claim 1, wherein the longitudinal core and the first cladding have a generally circular cross-section.

3. The multi-cladding optical fiber of claim 2, wherein the second and external claddings have a non-circular cross-section.

4. The multi-cladding optical fiber of claim 1, wherein the longitudinal core and the first cladding have a generally oval cross-section.

5. The multi-cladding optical fiber of claim 4, wherein the second and external claddings have a generally circular cross-section.

6. The multi-cladding optical fiber of claim 1, wherein the longitudinal core is offset with respect to a longitudinal axis of the optical fiber.

7. The multi-cladding optical fiber of claim 1, wherein the external cladding has an external cladding refractive index lower than the second cladding refractive index.

8. The multi-cladding optical fiber of claim 7, further comprising at least one intermediate cladding surrounding the second cladding and being surrounded by the external cladding.

9. The multi-cladding optical fiber of claim 8, wherein the at least one intermediate cladding has an intermediate cladding refractive index lower than the second cladding refractive index and higher than the external cladding refractive index.

10. The multi-cladding optical fiber of claim 8, wherein the at least one intermediate cladding has a non-circular cross-section.

11. The multi-cladding optical fiber of claim 1, wherein the core comprises an element selected from the group consisting of silica, aluminum, germanium, phosphorus, boron and fluorine.

12. The multi-cladding optical fiber of claim 1, wherein the rare-earth dopant comprises an element selected from the group consisting of ytterbium, erbium, neodymium, thulium and praseodymium.

13. The multi-cladding optical fiber of claim 1, wherein the first and second claddings independently comprise an element selected from the group consisting of silica, aluminum, germanium, phosphorus, boron and fluorine.

14. The multi-cladding optical fiber of claim 1, wherein the external cladding includes a low refractive index polymer.

15. The multi-cladding optical fiber of claim 8, wherein the at least one intermediate cladding comprises an element selected from the group consisting of glass and low refractive index polymers.

16. The multi-cladding optical fiber of claim 1, wherein the core refractive index has a generally uniform profile.

17. The multi-cladding optical fiber of claim 1, wherein the core refractive index has a generally graded profile.

18. The multi-cladding optical fiber of claim 1, wherein the core refractive index has a generally parabolic profile.

19. The multi-cladding optical fiber of claim 1, wherein the core is configured as to be polarization maintaining.