초록 ▼

In a soot-deposition container, raw material gas and at the tip of a starting glass rod, combustion gas, and carrier gas are supplied to a core-depositing burner and raw material gas, combustion gas, carrier gas, and gas for doping of fluorine are supplied to a cladding-depositing burner, thereby fo

In a soot-deposition container, raw material gas and at the tip of a starting glass rod, combustion gas, and carrier gas are supplied to a core-depositing burner and raw material gas, combustion gas, carrier gas, and gas for doping of fluorine are supplied to a cladding-depositing burner, thereby forming porous glass soot comprised of glass soot for core and glass soot for cladding. With growth of soot, the supply amount of the fluorine-doping gas is increased while supply amounts of the other gases are kept constant. Next, dehydration process and transparentizing process of soot are carried out to obtain a glass preform for optical fiber. Fabricated in this way is the glass preform for optical fiber having the silica glass portion doped with low-concentration fluorine with high uniformity in the growth direction.

대표청구항 ▼

[ What is claimed is:] [1.] A method of fabricating a glass preform for optical glass fibers having a silica glass portion doped with fluorine by vapor phase axial deposition, comprising the steps of:(a) introducing a glass raw material gas and a fluorine compound gas into an oxyhydrogen flame;(b) d

[ What is claimed is:] [1.] A method of fabricating a glass preform for optical glass fibers having a silica glass portion doped with fluorine by vapor phase axial deposition, comprising the steps of:(a) introducing a glass raw material gas and a fluorine compound gas into an oxyhydrogen flame;(b) depositing fine glass particles in a direction of a target axis by flame hydrolysis;(c) growing a deposit body of said fine glass particles in said direction of the target axis, wherein a period of growth of said deposit body of the fine glass particles further comprises a period during which an initial flow rate of said fluorine compound gas (V.sub.1) introduced into said oxyhydrogen flame is monotonically and linearly increased to a final flow rate of said fluorine compound gas (V.sub.2); and(d) heating to transparentize said deposit body of said fine glass particles.