Optical fiber for delivering optical energy to or from a work object

• US 20050265678A1
• Filed: 05/02/2005
• Published: 12/01/2005
• Est. Priority Date: 05/03/2004
• Status: Active Grant

• Current Assignee: Nufern (Coherent Corp.)
• Original Assignee: Nufern (Coherent Corp.)
• Inventors: Tankala, Kanishka, Manyam, Upendra H., Seifert, Martin
• Granted Patent: US 7,317,857 B2
• Time in Patent Office: Days
• US Class Current: 385/127
• CPC Class Codes: G02B 6/02033 Core or cladding made from organic material, e.g. polymeric material G02B1/04 takes precedence
• CPC Class Codes: G02B 6/02038 with core or cladding having graded refractive index
• CPC Class Codes: G02B 6/0288 Multimode fibre, e.g. graded index core for compensating modal dispersion
• CPC Class Codes: G02B 6/03611 Highest index adjacent to central axis region, e.g. annular core, coaxial ring, centreline depression affecting waveguiding
• CPC Class Codes: G02B 6/0365 arranged - - +
• CPC Class Codes: G02B 6/14 Mode converters

Abstract

An optical fiber can include a glass core that is multimode at a selected wavelength and that comprises an index of refraction and a diameter D_core, a glass cladding disposed about said glass core, said glass cladding comprising an outer diameter D_cladding and a first index of refraction that is less than said index of refraction of said core, and a second cladding disposed about said glass cladding, said second cladding comprising an optically cured polymer, said polymer comprising an index of refraction that is less than said first index of refraction. In certain embodiments, the fiber can include various other features. For example, [D_cladding/D_core]² can be no greater than 1.5; the polymer can have a modulus of no greater than 100 MPa; the core can include means for affecting the power distribution amongst modes propagated by the core, such as by having a non circular outer perimeter; the core can support at least 100 modes at the selected wavelength; D_core can be at least 250 microns; the fiber can include a region disposed about the second cladding, and the region can comprise a polymer comprising an index of refraction that is greater than the index of refraction of said core. The fiber can be used, for example, for delivering light having the selected wavelength to or from a work object.

Claims

1. An improved optical fiber for delivering light having a selected wavelength to or from a work object, comprising;

a glass core that is multimode at the selected wavelength, said core comprising an index of refraction and a diameter D_core;

a glass cladding disposed about said glass core, said glass cladding comprising an outer diameter D_cladding and a first index of refraction that is less than said index of refraction of said core, where [D_cladding/D_core]² is no greater than 1.5, and wherein if one or both of said diameters D_core and D_cladding have a maximum and a minimum value, the maximum value is used in the foregoing formula; and

a second cladding disposed about said glass cladding, said second cladding comprising an optically cured polymer, said polymer comprising an index of refraction that is less than said first index of refraction and having a modulus of no greater than 100 MPa.

2. The optical fiber of claim 1 wherein said modulus is no greater than 50 MPa.

3. The optical fiber of claim 1 wherein said modulus is no greater than 10 MPa.

4. The optical fiber of claim 1 comprising a region surrounding said second cladding, said region comprising a selected polymer comprising an index of refraction that is greater than said index of refraction of said optically cured polymer.

5. The optical fiber of claim 4 wherein said selected polymer comprises a modulus that is no less than 500 MPa.

6. The optical fiber of claim 1 wherein said core consists essentially of silica glass.

7. The optical fiber of claim 1 wherein D_core is at least 250 microns.

8. The optical fiber of claim 1 wherein said core and said cladding are drawn from a preform.

9. An improved high power optical fiber for delivering light having a selected wavelength to or from a work object, comprising:

a glass core comprising silica, said glass core being multimode to the extent that it can support at least 100 modes at the selected wavelength, said core comprising an index of refraction and a diameter D_core that is at least 250 microns;

a glass cladding disposed about said glass core, said glass cladding comprising silica, said cladding comprising an index of refraction that is less than said index of refraction of said core;

a second cladding disposed about said glass cladding, said second cladding comprising an optically curable polymer, said optically cured polymer comprising an index of refraction that is less than said first index of refraction and having a modulus of no greater than 100 MPa.

a region disposed about said second cladding, said region comprising a polymer comprising an index of refraction that is greater than said index of refraction of said core.

10. The optical fiber of claim 9 wherein said fiber comprises an index of refraction profile of said core relative to said cladding, said index of refraction profile comprising a step index of refraction profile.

11. The optical fiber of claim 9 wherein said glass cladding further comprises a diameter D_cladding, where [D_cladding/D_core]² is no greater than 1.5, wherein if one or both of said diameters D_core and D_cladding have a maximum and a minimum value, the maximum value is used in the foregoing formula.

12. The optical fiber of claim 9 wherein D_core is at least 500 microns.

13. An improved optical fiber for the delivery of optical energy to or from a work object, comprising:

a multimode core, said core comprising a diameter D_core;

a cladding disposed about said core, said cladding further comprising an outer diameter D_cladding, where [D_cladding/D_core]2 is no greater than 1.5, and where if one or both of said diameters and D_core and D_cladding have a maximum and a minimum value, the maximum value is used in the foregoing formula; and

wherein said core comprises a non circular outer perimeter.

14. The optical fiber of claim 13 wherein said core consists essentially of silica.

15. The optical fiber of claim 13 wherein said core comprises a step index of refraction profile.

16. The optical fiber of claim 13 wherein a majority of the length of said outer perimeter conforms to a circle having a substantially constant radius.

17. The optical fiber of claim 13 wherein said cladding comprises a polymer.

18. The optical fiber of claim 13 wherein said cladding comprises a glass.

19. The optical fiber of claim 13 wherein said cladding comprises an index of refraction, said fiber further comprising a second cladding disposed about said cladding, said second cladding comprising a second index of refraction that is less than said first index of refraction.

20. The optical fiber of claim 13 wherein said outer perimeter comprises at least one inwardly oriented section.

21. The optical fiber of claim 13 wherein said outer perimeter comprises at least one straight section.

22. The optical fiber of claim 13 wherein said outer perimeter comprises an outwardly curved section having a first radius of curvature and another outwardly curved section having a second radius of curvature that is different than said first radius of curvature.

23. An improved optical fiber for the delivery of optical energy to or from a work object, comprising:

a multimode core, said core comprising a diameter D_core;

a cladding disposed about said core, said cladding further comprising an outer diameter D_cladding, where [D_cladding/D_core]² is no greater than 1.5, and where if one or both of said diameters and D_core and D_cladding have a maximum and a minimum value, the maximum value is used in the foregoing formula; and

wherein said core comprises means for affecting the power distribution amongst modes propagated by said core of said fiber.

24. The optical fiber of claim 23 wherein said means comprises at least one region of said core comprising an index of refraction that is different than the index of refraction of at least a portion of the core contacting said region.

25. The optical fiber of claim 23 wherein said means comprises the outer perimeter of said core being non-circular.

26. The optical fiber of claim 23 wherein said core has an outer perimeter and wherein said means comprises at least one inwardly oriented section of said outer perimeter of said core.

27. The optical fiber of claim 23 wherein said core comprises an outer perimeter, and wherein at least the majority of the length of said outer perimeter conforms to a circle having a substantially constant radius.

28. The optical fiber of claim 23 wherein said means comprises said core having at least one region comprising an index of refraction that is different than the index of refraction of at least a portion of the core contacting said region.

29. The optical fiber of claim 28 wherein said optical fiber extends along a longitudinal axis, and where said at least one region extends along said longitudinal axis.

30. The optical fiber of claim 28 wherein said at least one region comprises a void.

31. The optical fiber of claim 28 wherein said at least one region comprises a plurality of regions that are not coextensive with said core along the longitudinal direction.

32. The optical fiber of claim 23 wherein said means comprises said core having an inner region comprising a first index of refraction and a second region disposed about said inner region, said second region comprising a second index of refraction that is greater than said first index of refraction.

34. The optical fiber of claim 23 wherein said means comprises said core having a generally concave index of refraction profile.

33. The optical fiber of claim 33 wherein said inner region comprises a diameter and wherein said outer region comprises an outermost diameter, and wherein said diameter is greater than the difference between said outermost diameter and said diameter.

35. An improved optical fiber for the delivery of optical energy to or from a work object, comprising:

a multimode core, said core comprising a diameter D_core;

a cladding disposed about said core, said cladding further comprising an outer diameter D_cladding, where [D_cladding/D_core]² is no greater than 1.5, and where if one or both of said diameters and D_core and D_cladding have a maximum and a minimum value, the maximum value is used in the foregoing formula;

said core comprising an inner region comprising a first index of refraction and a second region disposed about said inner region, said second region comprising a second index of refraction that is greater than said index of refraction of said inner region by a selected amount; and

wherein said cladding comprises an index of refraction that is less than said first and second indices of refraction.

36. An improved optical fiber for the delivery of optical energy to or from a work object, comprising:

a multimode core for propagating light having selected operating wavelength, said core supporting at least 200 modes at said operating wavelength;

said core comprising an inner region comprising a first index of refraction and a second region disposed about said inner region, said second region comprising a second index of refraction that is greater than said index of refraction of said inner region by a selected amount; and

a cladding disposed about said core, said cladding comprising an index of refraction that is less than said first and second indices of refraction.