Optical fiber having reduced defect density

1. An optical fiber for delivering optical energy including a selected wavelength to or from a work object, comprising:

a multimode glass core comprising a diameter of at least 250 microns, said core having an index of refraction;

a polymer cladding having a thickness and contactingly surrounding a glass portion of said fiber so as to define an interface between said glass portion and said polymer cladding, said polymer cladding comprising a first index of refraction that is less than said index of refraction; and

wherein said fiber comprises a density of less than 0.25 non-conforming regions having a diameter of 25 microns or greater per millimeter of length along said fiber, each of said non-conforming regions being a region visible to the human eye under an optical microscope and having at least a portion thereof within a selected distance of said interface, said distance being less than or equal to said thickness of said polymer cladding, said optical microscope having a total magnification of about 200.

2. The optical fiber of claim 1 wherein said density is less than 0.1 non-conforming regions per millimeter of length along said fiber.

3. The optical fiber of claim 1 wherein said density is less than 0.05 non-conforming regions per millimeter of length along said fiber.

4. The optical fiber of claim 1 wherein said density is less than 0.25 non-conforming regions having a diameter of 10 microns or greater per millimeter of length along said fiber.

5. The optical fiber of claim 1 wherein said polymer cladding comprises a hard polymer.

6. The optical fiber of claim 1 wherein said polymer cladding comprises one of an HCS and a TECS material.

7. The optical fiber of claim 1 comprising another cladding disposed about said core, said another cladding comprising a second index of refraction that is less than said index of refraction and greater than said first index of refraction, and wherein said polymer cladding is disposed about said another cladding.

8. The optical fiber of claim 7 wherein said core comprises a diameter D core and wherein said another cladding 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.

9. An optical fiber for delivering optical energy including a selected wavelength to or from a work object, comprising:

a multimode glass core comprising a diameter of at least 250 microns, said core comprising an index of refraction;

a polymer cladding contactingly surrounding a glass portion of said fiber, said polymer cladding comprising a first index of refraction that is less than said index of refraction; and

wherein said polymer cladding is applied to at least a part of said fiber in at least a class 1000 environment; and

wherein said polymer cladding has a thickness and forms an interface with said glass portion of said fiber, and wherein said fiber comprises a density of less than 0.25 non-conforming regions having a diameter of 25 microns or greater per millimeter of length along said fiber, each of said non-conforming regions being a region visible to the human eye under an optical microscope and having at least a portion thereof within a selected distance of said interface, said distance being less than or equal to said thickness of said polymer cladding, said optical microscope having a total magnification of about 200.

10. A method of delivering light to or from a work object, comprising:

providing a source of optical energy;

providing an optical fiber comprising a glass core having a diameter of at least 250 microns and an index of refraction, a polymer cladding contactingly surrounding a glass portion of the optical fiber so as to form an interface between the polymer cladding and the glass portion, the polymer cladding comprising a first index of refraction that is less than the index of refraction, wherein the optical fiber comprises a density of less than 0.25 non-conforming regions having a diameter of 25 microns or greater per millimeter of length along the optical fiber, each of the non-conforming regions being a region visible to the human eye under a microscope and having at least a portion thereof within a selected distance of the interface, the distance being less than or equal to the thickness of the polymer cladding, the optical microscope having a magnification of about 200; and

receiving with the optical fiber optical energy from the source and guiding the optical energy with the optical fiber, wherein the optical energy comprises at least one of 1) pulses each comprising a peak power of at least 10 kW, 2) an average power of at least 50 Watts, or 3) an average power density of at least 2.9 kW/cm 2 .

11. The method of claim 10 wherein the optical energy comprises the pulses having a peak power of at least 10 kW.

12. The method of claim 10 wherein the optical energy comprises the average power of at least 50 Watts.

13. The method of claim 10 wherein the optical energy comprises the average power density of at least 2.9 kW.

14. The method of claim 10 wherein the density is less than 0.1 non-conforming regions per millimeter.