METHOD FOR MANUFACTURING CORE GLASS PREFORM FOR OPTICAL FIBER

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing a core glass preform for an optical fiber restrained from reattaching of a dopant on an outer periphery of a porous preform wherein the unevenness of a concentration distribution is little, capable of controllingαpower and hardly generating a crack. SOLUTION: The method for manufacturing the core glass preform for an optical fiber is that the porous preform 1 is formed: a 1st burner 5 blows glass raw material gas, dopant raw material gas and combustion gas upward to a rotating quartz seed rod 2; a glass fine particle produced by flame hydrolysis reaction is deposited in axial direction while forming a porous glass preform 1; the preform 1 is dehydrated, sintered and vitrified into transparent glass. Wherein the angle made by a central axis Z1 of the 1st burner 5 and the axial line Y of the porous glass preform is made to be <=10 deg..