STORAGE OF POROUS PREFORM FOR OPTICAL FIBER

摘要

PURPOSE:To prevent generation of clouding in sintering and vitrification process and to improve the yield of preform for optical fiber, by storing a porous preform in an atmosphere having a humidity below a specific level during the period from the preparation of a porous preform by vapor axial deposition process to the sintering and vitrification step. CONSTITUTION:A feed gas such as SiCl4 or GeCl4 is supplied together with oxygen and hydrogen to a torch 3 and is hydrolyzed in an oxyhydrogen flame to form soot of an oxide, which is deposited on the tip end of a rotating quartz rod 4 used as a target. The quartz rod 4 is pulled up under deposition of soot to obtain a porous preform 5. The storage of the porous preform 5 during the period from the preparation of the porous preform 5 to the sintering and vitrification step is carried out in an environment having a relative humidity of <=50%. The stored preform 5 is sintered and vitrified to obtain an optical fiber preform preventing the occurrence of clouding phenomenon caused by water adsorbed in the glass during storage.