| 摘要 |
PURPOSE:To obtain optical fiber which is stable for a long time hardly causing increase of transmission loss even if it is placed in the atmosphere of H2 by pretreating a preform rod by heating it in the atmosphere of gaseous halogen at lower temp. than spinning temp. and spinning the preform rod thereafter. CONSTITUTION:Gaseous halogen (e.g. fluorine) along or a gaseous mixture 8 consisting of >=50vol% gaseous halogen and inert gas (e.g. Ar) is fed to a pretreating furnace 2 as atmosphere gas, and the gas is heated by a heater 6 to ca. 450-1,600 deg.C which is lower than the spinning temp. A preform rod 1 of quartz base provided at least with core part is inserted into the pretreating furnace 2 at low speed condition, and the preform rod 1 is pretreated by heating. Next, the preform rod 1 is introduced into a spinning furnace 3 and inert gas 9 is supplied thereto, and the rod is melted by heating at ca. 2,000 deg.C with a heater 7 and spun. Thus, aimed optical fiber 12 is prepd. |
