| 摘要 |
PURPOSE:To obtain a base material for an optical fiber having a low OH group concn. and causing a small loss by manufacturing porous base material of low bulk density by the VAD method, presintering the base material at a temp. at which it is not converted into transparent glass in an inert gas, and converting the presintered body into transparent glass by finish sintering. CONSTITUTION:Starting materials and fuels such as SiCl4, GeCl4, POCl3, Ar, H2 and O2 are fed to an uprighted burner 1 and burned, and fine oxide particles formed by hydrolysis are deposited on the tip of a quartz rod target 19 above the burner 1 to grow a porous base material 7 of 0.2g/cc bulk density. The base material 7 is presintered at 1,000-1,250 deg.C at which it is not converted into transparent glass in an inert gas such as He in a carbon core tube 22. The presintered body is converted into transparent glass by finish sintering at a temp. above the presintering temp. in an inert gas to obtain the desired base material for an optical fiber. |
