| 摘要 |
PURPOSE:To obtain an optical fiber preform having excellent characteristics, preventing the formation of bubbles at the glass interface and the intrusion of moisture into the preform, by preheating a glass rod with a flame containing chlorine or its compound, and depositing a glass layer to the circumference. CONSTITUTION:The glass rod 6 ascending slowly under rotation is preheated at a high temperature by a flame containing chlorine (compound) which does not form a glass raw material, e.g. SOCl2, etc. using a preheating burner 3. Glass soot formed by the vapor-phase reaction, i.e. flame hydrolysis reaction by the glass-forming burners 4, 5 is deposited to the outer circumference of the preheated glass rod 6 to form a porous glass layer 7. Since the glass rod 6 is preheated, the glass soot can be deposited firmly to the rod. Thereafter, the glass layer 7 is converted to a transparent glass layer by the thermal treatment in an electrical furnace (1,400 deg.C) in a mixed atmosphere consisting of e.g. H and a small amount of SOCl2. |
