Patent ID: 8718430

Claim:
A double clad optical fiber having a waveguide core, an inner waveguide cladding around the core having an inner cladding refractive index, and an outer waveguide cladding around the inner cladding having an outer cladding refractive index lower than the inner cladding refractive index, and a jacket around the outer waveguide cladding having a jacket refractive index, the optical fiber having a portion extending along its length along which the outer waveguide cladding and the jacket are absent, the portion having corresponding faces of the outer waveguide cladding at two lengthwisely opposite ends of the portion, and having a sealant extending along the entire length of the portion, the sealant impeding lengthwise diffusion of environmental water through both faces, into the outer waveguide cladding.