| 摘要 |
<p>A heating furnace in which a porous glass material for optical fiber, which consists of fine quartz glass particles, is heat-treated in a fluoride-containing gaseous atmosphere so as to add fluorine thereto and make it transparent and obtain a glass material for optical fiber. This heating furnace is constituted of heating elements and a furnace core tube provided on the inner side of the heating elements so as to isolate the heating atmosphere and heating elements from each other, and is characterized in that at least the inner layer of the furnace core tube is formed of high-purity carbon.</p> |
