PURPOSE: Glass is deposited by vapor-phase chemical reaction using SiCl4 and GeCl4 and a low-volatile vaporized substance with higher refractive index than GeO2 is fed into the innermost part to produce a parent material for optical fiber free from dip-formation.
CONSTITUTION: SiCl4 in the tank 1 is vaporized by bubbling it with O2 fed from pipe 4 and fed from pipe 5 into the rotating quartz glass tube 11, and simultaneously the tube 11 is heated with oxyhydrogen flame burner 12 from outside to deposite synthetic glass for SiO2 clad by vapor-phase chemical reac tion. Then, the dopant of GeCl4 is vaporized from the tank 2 and mixed to deposite synthetic glass for the core 15. Then, in the formation of the innermost part 16, a metal halide which forms an oxide of lower volatile than GeO2 and has a refractive index equal to or higher than GeO2 is vaporized and fed into the vapor-phase chemical reaction system 10 by 5W15wt% as a refractive index compensator. Thus, a parent material free from dip formation in the core is obtained.
NISHIMURA MASAO
IINO AKIRA
KAMIYA TAMOTSU
