PRODUCTION OF BASE MATERIAL FOR OPTICAL FIBER

摘要

PURPOSE:To produce the titled base material excellent in quality in a short time, by feeding sol obtained by hydrolyzing both high-purity silica powder and silicon alkoxide around a specified gel-like molded form, removing water and a solvent and thereafter calcining it. CONSTITUTION:A gel-like molded form is obtained by adding both water of 0.5-2.0 times mol. for alkoxy group and acid of 0-0.5 times mol. for water or alkali of 0-1.0 time mol. thereafter to the mixture of silicon alkoxide and germanium alkoxide having 0.03-0.91 Ge/Si atomic ratio and hydrolyzing the obtained mixture at 0-100 deg.C to form gel. Then the above-mentioned molded body is arranged in the center of a large cylindrical vessel to form a core part and sol obtained by hydrolyzing the mixture of silicon alkoxide and high- purity silica powder having 0.1-10mum particle diameter of 0.5-5 times weight is fed arround it to allow the sol to gel and thereafter supercritical fluid (e.g. CO2) is fed under the supercritical conditions and a molded form having a porous cladding layer is obtained by removing water and a solvent. Then this molded form is calcined at >=700 deg.C in the dry atmosphere.