| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and an apparatus capable of preventing characteristic deterioration of optical fibers caused by generated OH groups in optical preforms inserted in a heating furnace and stably manufacturing glass wire materials having high quality. SOLUTION: In drawing process which makes glass preforms to glass wire materials, the specific humidity of peripheral atmosphere of glass preforms 1 inserted in the heating furnace 10 is held in 0.05 g/kg or less. Thereby, H<SB>2</SB>O or OH group of peripheral atmosphere of the glass preform 1 is prevented from dissolving and diffusing in the glass preform inside part during a heating process, and the residual OH amount of the manufactured optical fibers can be reduced. An inert gas is introduced to the heating furnace 10 and/or purge boxes 13, 18, and by controlling the introductory flow amount, the internal pressure of the heating furnace 10 is held higher than the external pressure not to flow the external gas into the heating furnace 10. COPYRIGHT: (C)2004,JPO |
