OPTICAL FIBER AND ITS PRODUCTION

摘要

PURPOSE: To obtain an optical fiber restrained from increasing transmission loss over a long period due to hydrogen diffusion by providing a specific silica glass layer as the outermost layer of the clad portion of a quartz-based single mode fiber followed by forming a carbon film thereon. CONSTITUTION: This optical fiber has a silica glass layer as the outermost layer of the clad portion and a carbon film outside the layer. The silica glass layer contains at least one element, except Si and O, selected from Al, B and P, each belonging to groups other than group XIV in the periodic table and differing in valence from Si and has a thickness >=0.5 times the radius of the fiber. This optical fiber is obtained by using a glass preformed material which is made by sintering a glass fine particle build-up body 4 with a diameter of 100mm prepared by depositing glass fine particles on a starting rod composed of chore portion consisting of GeO2 -contg. SiO2 and clad portion of SiO2 so as to be 1mmHg in the partial pressure of AlCl3 as an additive element (compound) in a sintering oven where a heater 1 having the AlCl3 inside is brought to 100 deg.C.