| 摘要 |
PURPOSE:To prevent the deterioration of an SiC film on a furnace core tube and to stably produce a base material for optical fiber for a long period by subjecting a base material composed of porous glass to heat treatment in the presense of a gaseous mixture of inert gas and silicon halide, in a furnace core tube made of carbon coated with SiC film, and then to heat treatment in the presence of specific fluorine compound. CONSTITUTION:A gaseous mixture 17 of inert gas and silicon halide, (or a gaseous mixture prepared by further adding halogen series gas to both gases mentioned above), is introduced into a furnace core tube 12 made of carbon coated with SiC film 19 (19: carbon-base material) and a base material 11 composed of porous glass is subjected to dehydration and high purification treatment. Subsequently, a fluorine compound 17 prepared by mixing Si2F6 and/or Si3F8 with SiF4 is introduced into the furnace core tube 12 and fluorine addition treatment is applied to the above base material 11 composed of porous glass after the above dehydration and high purification treatment, followed by transparent vitrification treatment. |
