Optical fiber having a bragg grating formed in its cladding

An optical waveguide comprising:

• a core formed of silica that is substantially free of dopants;
• an inner cladding being disposed about the core, the inner cladding including an index-lowering dopant, wherein the refractive index of the inner cladding is lower than the refractive index of the core;
• an outer cladding being disposed about the inner cladding, wherein the refractive index of the outer cladding is greater than the refractive index of the inner cladding;
• and
• a grating being disposed only in the inner cladding.

A method for providing an optical waveguide including a Bragg grating disposed only in a cladding of the optical waveguide, the method comprising:

• a) providing an optical waveguide including a core disposed within the cladding, the core being formed of silica that is substantially free of dopants;
• b) doping a portion of the cladding with an index-lowering dopant;
• c) doping a length of the portion of the cladding with a photosensitizing dopant;
• and
• d) forming a Bragg grating only in a portion of cladding that is doped with the photosensitizing dopant.

A method for providing an optical waveguide including a Bragg grating disposed only in a cladding of the optical waveguide, the method comprising:

• a) providing an optical waveguide including a core disposed within the cladding, the core being formed of silica that is substantially free of dopants;
• b) doping a portion of the cladding with an index-lowering dopant;
• c) photosensitizing a length of the portion of the cladding;
• and
• d) forming a Bragg grating only in a portion of cladding that is doped with the photosensitizing dopant.