| 摘要 |
PROBLEM TO BE SOLVED: To enable the production of an optical fiber that is reduced in OH group content and is excellent in light-transmission characteristics by placing glass starting materials or porous glass material formed by depositing fine glass particles and heavy water in a pressure and heating vessel, heating them until the vessel is saturated with the water vapor under pressure and continuing the heating in an inert gas atmosphere containing heavy water. SOLUTION: Raw materials for glass or a porous glass soot body formulated to a desired composition 9 and heavy water in an amount of 3-10wt.% based on the porous soot body are charged in a crucible 8 and they are mixed. Then, the crucible is placed in a pressure and heating vessel 12 having a heater 11 embedded therein and heated at the temperature that can saturate the vessel 12 with the steam under the pressure of about 5-10kgf/cm<2> (at 150-240 deg.C) for more than 2 days. Then, the glass raw materials or porous glass soot 9 in the crucible 8 is dried, taken out of the pressure vessel 12, transferred to another heating furnace and heated in an inert gas atmosphere or the same containing heavy water at 500-1,000 deg.C for more than 2 hours. |
