| 摘要 |
PURPOSE:To readily obtain the subject air bubble-free glass preform for an optical fiber by forming a porous glass layer of pure silica on the outer periphery of a pure silica glass rod or tube in advance, making a porous glass layer doped with GeO2 on the outer periphery thereof and heating the resultant layered glass for making it transparent. CONSTITUTION:Oxygen gas and hydrogen gas are supplied to an oxyhydrogen flame burner 2 to form an oxyhydrogen flame and a gaseous raw material (e.g. SiCl4) of glass is supplied to the central part of the burner 2. Silica fine particles are generated by flame hydrolysis and a porous glass layer 3 of pure silica is formed on the outer periphery of a pure silica glass rod or pipe 1. A porous glass layer 4 doped with germanium oxide is then formed on the outer periphery of the resultant porous glass layer 3 and the obtained layered glass is subsequently heated and made transparent, thus obtaining the objective glass preform for an optical fiber. By using the above-mentioned method, generation of foams accompanying vaporization of germanium in the process for formation of the transparent glass can be prevented. |
