MANUFACTURE OF OPTICAL FIBER PREFORM

摘要

PURPOSE:To manufacture an optical fiber preform having uniform refractive index distribution and excellent transmission characteristics, by blasting SiCl4 gas containing GeCl4 through the plural nozzles of a concentric multiple tube burner controlling the feeding rate of GeCl4 through each nozzle to different levels from each other. CONSTITUTION:A raw material gas SiCl4 containing a large amount of a dopant GeCl4 is blasted through the central nozzle of a concentric multiple tube burner, and an SiCl4 gas containing a small amount of GeCl4 is blasted through the ring nozzle (forming the second layer). A combustible gas is burnt to synthesize glass fine powder by the flame hydrolysis. The powder is transferred and deposited to the starting material rod, and successively grown along the axial direction to obtain the objective optical fiber preform. The refractive index distribution parameter can be controlled by controlling the ratio of the amount of the added GeCl4 per unit volume of the raw material gas supplied from the central nozzle to that of the GeCl4 in the gas supplied from the ring nozzle.