PURPOSE: To manufacture the source material of an optical fiber superior in performance by reducing a gas ejection end in diameter at the time of forming a light transmitting glass layer in the inside of a hollow quartz glass tube and eliminating voids in the process of manufacturing an optical fiber source material by the internal CVD method.
CONSTITUTION: A quartz glass tube is fixed to a glass lathe 2 and rotated. Gaseous SiCl4, POCl3, and GeCl4 are fed together with oxygen into the rotating tube 1, and the outside of the tube 1 is heated with an oxygen hydrogen burner 4. Oxidation reaction is caused by heating said gas mixture, fine glass powder is produced, attached to the inside of the tube 1, and melted to form a transparent glass layer 5. Said gas mixture is substituted for chlorine and oxygen gases, and the end of the tube 1 on the gas ejection side is reduced in the inside diameter by heating before eliminating the inner void by heating. In the course of eliminating the void, moisture and the like in the air are prevented from reversely invading into the tube through the narrowed part 21, and the obtained optical fiber source material has superior characteristics.
TSUKAMOTO MAKOTO
YUASA MITSUO
