METHOD FOR MANUFACTURING RAW MATERIAL OF OPTICAL FIBER

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing a raw material of optical fiber whose difference of specific refractive indexes of a longer direction is uniform. SOLUTION: A difference of specific refractive indexes of optical fiber processed from a raw material 5 of optical fiber is inversely proportional to the change of speed of pulling up. In making use of a relation of the inversely proportion, a raw material of optical fiber whose difference of the specific refractive indexes of a longer direction is uniform is made by the feedback controlling a quantity of dopant which changes the refractive index of the optical fiber.