| 摘要 |
PROBLEM TO BE SOLVED: To provide the production of the precursor provided with a quartz glass section which is doped with a low concn. of fluorine so as to enhance uniformity of the fluorine doping with respect to the growth direction of glass soot. SOLUTION: In this production, at the tip of a starting material glass rod 300 in a soot deposition vessel 400, a gaseous raw material, a combustion gas and a carrier gas are supplied to a burner 510 for depositing a core and also, a raw material gas, a combustion gas, a carrier gas and a gas for fluorine doping are supplied to a burner 520 for depositing a cladding to form porous glass soot consisting of core glass soot 100 and cladding glass soot 200. At this time, the supply amount of the gas for fluorine doping is increased with the growth of glass soot while keeping supply amounts of the other gases constant. Then, the resulting soot is subjected to dehydration treatment and transparentization treatment to produce the objective precursor of an optical fiber glass preform. |
