PURPOSE: To manufacture a preform for an optical fiber contg. F by forming an SiO2-base hollow cylindrical porous glass body by a VAD method and by making it transparent by sintering in an atmosphere contg. F.
CONSTITUTION: The porous glass body 1 of SiO2 is deposited on the outside of a core rod 2 of quartz glass or ceramics such as Al2O3 or SiC with a burner 3 while slowly pulling up the rod 2 in a VAD apparatus. After pulling out the rod 2, the resulting hollow porous glass body 1 is sintered in an apparatus 4 provided with a heater 5. At this time, an He-base gaseous mixture contg. F-base gas is fed to the apparatus 4 from the inlet 6, and the He-base gaseous mixture contg. no F-base gas is introduced into the hollow of the glass body 1 from an introducing hole 8. The preform for an optical fiber contg. no F in the central region and having a concn. distribution of F in the peripheral part can be easily manufactured.
TANAKA GOUTAROU
KIYOUDOU TSUNEHISA
KANAMORI HIROO
MIZUTANI FUTOSHI
