| 摘要 |
PURPOSE:To minimize the influence of a heating furnace on an upper dummy rod and to effectively utilize a deposited soot. CONSTITUTION:A deposited soot l supported with a dummy rod at least at the upper end is slowly inserted into a heating furnace 14 to convert the soot into a transparent glass. In the above process for the production of an optical fiber preform, a cooling gas medium is introduced into the inside or outer circumference of the furnace core pipe 15 of the heating furnace 14 for the deposited soot 1 at a position slightly above the center of the soot to convert the soot into a transparent glass while preventing the temperature increase of the region near the upper part of the deposited soot 1 inserted into the furnace. The deposited soot 1 can be inserted into the heating furnace until the part near the upper end of the deposited soot l is deeply inserted into the core part of the heating region 16 to enable the effective production of a transparent glass even from the damaged part of the upper dummy rod 2a and from the soot part having effective outer diameter near the upper end of the deposited soot 1. |
