PRODUCTION OF OPTICAL FIBER AND ITS PREFORM

摘要

PURPOSE:To keep the difference in the refractive index between the core and clad at >=0.3% and to reduce the Reyleigh scattering loss by forming the optical fiber with the SiO2 core having the GeO2 content reduced to less than a specified value and the SiO2 clad contg. a specified amt. of F. CONSTITUTION:A porous glass layer consisting of SiO2 glass fine particles is deposited around the SiO2 core glass rod contg. <=2mol% GeO2 by flame hydrolysis or thermal oxidation to obtain a porous glass preform. The preform is then heat-treated at 1200-1400 deg.C in the He atmosphere contg. >=1.0% F ion. The preform is heated at 1600-1700 deg.C in the He atmosphere alone while the partial pressure of He in the atmosphere is made higher than that in the preform, and vitrified.