Optical fiber, optical fiber preform and method of fabricating same

摘要

An optical fiber capable of suppressing an increase of a transmission loss after exposure of the optical fiber to hydrogen or deuterium is provided. The optical fiber has a core region (1), an inner cladding region (2) surrounding the core region, a trench region (3) surrounding the inner cladding region, an outer cladding region (4) surrounding the trench region, and a refractive index varying region arranged between the inner cladding region and the trench region, the refractive index varying region (10) having a refractive index gradually increasing from the trench region to the inner cladding region.