Optical fiber, optical fiber preform, and method for manufacturing optical fiber preform

摘要

An improved method for manufacturing an optical fiber preform uses the CVD method in which a portion of or the whole of the optical fiber preform is formed by depositing glass on the inner wall of the starting tube. The method comprises a first step of depositing glass on the inner wall of the starting tube and collapsing the starting tube so that a silica rod is formed; a second step of removing the starting tube surrounding the silica rod or removing the starting tube and a part of synthetic glass; and a third step of depositing glass on an outer periphery of the silica rod obtained in the second step. By setting the refractive index of the cladding to be less than that of pure silica using the present method, an optical fiber having an extremely low transmission loss may be obtained.