Optical fiber with variable absorption

Patent metadata

Field	Value
Publication number	US-11175449-B2
Application number	US-201916657070-A
Country	US
Kind code	B2
Filing date	Oct 18, 2019
Priority date	Jan 2, 2019
Publication date	Nov 16, 2021
Grant date	Nov 16, 2021

Abstract

An optical fiber may comprise a core doped with one or more active ions to guide signal light from an input end of the optical fiber to an output end of the optical fiber, a cladding surrounding the core to guide pump light from the input end of the optical fiber to the output end of the optical fiber, and one or more inserts formed in the cladding surrounding the core. Each of the one or more inserts may have a geometry (e.g., a cross-sectional size, a helical pitch, and/or the like) that varies along a longitudinal length of the optical fiber, which may cause an absorption of the pump light to be modulated along the longitudinal length of the optical fiber.

First claim

What is claimed is:

1. An optical fiber, comprising:
a core doped with one or more active ions to guide signal light from an input end of the optical fiber to an output end of the optical fiber;
an outer cladding surrounding an inner cladding;
the inner cladding surrounding the core to guide pump light from the input end of the optical fiber to the output end of the optical fiber; and
one or more inserts in the inner cladding,
wherein each of the one or more inserts has a geometry that varies along a longitudinal length of the optical fiber,
wherein each of the one or more inserts is offset from the core, and
wherein the geometry of the one or more inserts is varied along the longitudinal length of the optical fiber to cause an absorption of the pump light to be modulated along the longitudinal length of the optical fiber.

2. The optical fiber of claim 1 , wherein the geometry of the one or more inserts that varies along the longitudinal length of the optical fiber comprises a cross-sectional size of the one or more inserts that increases from the input end to the output end of the optical fiber.

3. The optical fiber of claim 2 , wherein the cross-sectional size of the one or more inserts increases from the input end to the output end of the optical fiber to cause a pump scrambling rate to increase from the input end of the optical fiber to the output end of the optical fiber and thereby cause the absorption of the pump light to increase along the longitudinal length of the optical fiber.

4. The optical fiber of claim 3 , wherein the pump scrambling rate depends on a positioning of the one or more inserts relative to one or more of the core or a perimeter of the inner cladding.

5. The optical fiber of claim 1 , wherein at least one insert of the one or more inserts has a first refractive index, wherein the inner cladding has a second refractive index, wherein the first refractive index is higher than the second refractive index, and wherein a cross-sectional size of the at least one insert decreases from the input end to the output end of the optical fiber.

6. The optical fiber of claim 5 , wherein the first refractive index being higher than the second refractive index causes the pump light to be trapped in the at least one insert, and wherein the cross-sectional size of the at least one insert decreases from the input end to the output end of the optical fiber to cause the trapped pump light to be released downstream from the input end of the optical fiber and into the inner cladding along the longitudinal length of the optical fiber.

7. The optical fiber of claim 1 , wherein the optical fiber is to be pumped at multiple locations along the longitudinal length of the optical fiber, and wherein the geometry of the one or more inserts varies along the longitudinal length of the optical fiber to provide a decrease in the absorption of the pump light in one or more regions that are proximal to the multiple locations.

8. The optical fiber of claim 1 , wherein the geometry of the one or more inserts that varies along the longitudinal length of the optical fiber comprises a helical pitch that varies along the longitudinal length of the optical fiber.

9. The optical fiber of claim 1 , wherein the one or more inserts have a first refractive index that differs from a second refractive index of the inner cladding.

10. The optical fiber of claim 1 , wherein the one or more inserts comprise one or more cavities that contain one or more of a solid, a liquid, or a gas.

11. A method of forming an optical fiber, comprising:
providing a core doped with one or more active ions to guide signal light from an input end of the optical fiber to an output end of the optical fiber;
providing an inner cladding surrounding the core to guide pump light from the input end of the optical fiber to the output end of the optical fiber;
providing an outer cladding surrounding the inner cladding; and
providing one or more inserts in the inner cladding,
wherein each of the one or more inserts has a geometry that varies along a longitudinal length of the optical fiber,
wherein each of the one or more inserts is offset from the core, and
wherein the geometry of the one or more inserts is varied along the longitudinal length of the optical fiber to cause an absorption of the pump light to be modulated along the longitudinal length of the optical fiber.

12. The method of claim 11 , wherein the geometry of the one or more inserts that varies along the longitudinal length of the optical fiber comprises a cross-sectional size of the one or more inserts that increases from the input end to the output end of the optical fiber.

13. The method of claim 12 , wherein the cross-sectional size of the one or more inserts increases from the input end to the output end of the optical fiber to cause a pump scrambling rate to increase from the input end of the optical fiber to the output end of the optical fiber and thereby cause the absorption of the pump light to increase along the longitudinal length of the optical fiber.

14. The method of claim 13 , wherein the pump scrambling rate depends on a positioning of the one or more inserts relative to one or more of the core or a perimeter of the inner cladding.

15. The method of claim 11 , wherein at least one insert of the one or more inserts has a first refractive index, wherein the inner cladding has a second refractive index, wherein the first refractive index is higher than the second refractive index, and wherein a cross-sectional size of the at least one insert decreases from the input end to the output end of the optical fiber.

16. The method of claim 15 , wherein the first refractive index being higher than the second refractive index causes the pump light to be trapped in the at least one insert, and wherein the cross-sectional size of the at least one insert decreases from the input end to the output end of the optical fiber to cause the trapped pump light to be released downstream from the input end of the optical fiber and into the inner cladding along the longitudinal length of the optical fiber.

17. The method of claim 11 , wherein the optical fiber is to be pumped at multiple locations along the longitudinal length of the optical fiber, and wherein the geometry of the one or more inserts varies along the longitudinal length of the optical fiber to provide a decrease in the absorption of the pump light in one or more regions that are proximal to the multiple locations.

18. The method of claim 11 , wherein the geometry of the one or more inserts that varies along the longitudinal length of the optical fiber comprises a helical pitch that varies along the longitudinal length of the optical fiber.

19. The method of claim 11 , wherein the one or more inserts have a first refractive index that differs from a second refractive index of the inner cladding.

20. An optical fiber, comprising:
a core doped with one or more active ions to guide signal light from an input end of the optical fiber to an output end of the optical fiber;
a cladding surrounding the core to guide pump light from the input end of the optical fiber to the output end of the optical fiber; and
one or more inserts in the cladding,
wherein each of the one or more inserts has a geometry that varies along a longitudinal length of the optical fiber,
wherein the geometry of the one or more inserts is varied along the longitudinal length of the optical fiber to cause an absorption of the pump light to be modulated along the longitudinal lengt

Assignees

• Lumentum Operations Llc

Inventors

• Petit Vincent
• Muendel Martin H

Classifications

• H01S3/06745

  Tapering of the fibre, core or active region · CPC title

• G02B6/02376 Primary

  Longitudinal variation along fibre axis direction, e.g. tapered holes · CPC title

• G02B6/03672

  arranged - - + - · CPC title

• G02B6/03694 Primary

  Multiple layers differing in properties other than the refractive index, e.g. attenuation, diffusion, stress properties · CPC title

• H01S3/06708

  Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering (optical fibres as passive waveguides G02B6/02) · CPC title