| 摘要 |
PURPOSE:To obtain a rod-like preform for optical transmission lines having improved transmission characteristic, by providing the second quartz glass tube in a rotating quartz glass tube in introducing a raw material gas for forming glass into the quartz glass tube and oxidatively reacting the raw material gas by heat of a plasma flame generated in the quartz glass tube. CONSTITUTION:A gaseous raw material 5 for forming glass is introduced from one end to the other of a quartz glass tube 1 rotating on the central axis as an axis. A plasma flame is generated in the quartz glass tube 1 by high-frequency energy (high-frequency coil 3) supplied from the outside of the quartz glass tube 1. The raw material is oxidatively reacted by heat of the plasma flame to give glass, which is hen deposited on the inner surface of the quartz glass tube 1 and afford the aimed rod-like preform for optical transmission lines. In the above-mentioned construction, th second quartz glass tube 2 is placed in the quartz glass tube 1 to generate the plasma flame in the second quartz glass tube 2. |
