| 摘要 |
PURPOSE:To obtain an optical fiber which can be exposed to a high-temperature environment for a long period without increasing the transmission loss caused by the hydroxyl group, by melt-spinning an optical fiber preform having a specific hydroxyl group-content in a specific atmosphere, and coating the fiber with a metal. CONSTITUTION:An anhydrous glass preform 9 is attached in the preform-feeing zone 4, and the lower end of the preform is positioned to the level of the heater 1b. Molten metal 10 such as aluminum, indium, etc. is supplied from the molten metal reservior 8 to the crucible 7. High-purity dried argon gas or helium gas which may contain a small amount of dry halogen gas, is introduced through the gas inlet 5 into the apparatus. The end part of the glass preform 9 is melted by the heater 1b, and the spun optical fiber 11 is introduced continuously into the crucible 7 containing the molten metal to obtain the objective metal-coated optical fiber 12. Since the inner space of the apparatus is shielded completely from the outer atmosphere, and is supplied with dry gas or dry halogen-containing gas, the atmosphere in the apparatus is maintained to the perfect anhydrous state or the dehydrated state by the halogen gas. |
