| 摘要 |
PURPOSE:To uniformize the diameter of a drawn optical fiber by practically equalizing the clearance between a furnace core tube and a preform to the clearance between the furnace core tube and a pipe, heating and melting the lower end of the preform, and drawing an optical fiber. CONSTITUTION:The pipe 6 is made of the same material as that of the furnace core tube 3, and heated by the radiant heat from the furnace core tube 3 to almost the same temp. In addition, since the clearance between the preform 1 and the furnace core tube 3 is almost equalized to the clearance between the pipe 6 and the furnace core tube 3, an eddy current of gaseous nitrogen is not caused. Accordingly, the gaseous nitrogen shown by the arrow A1 is kept at a uniform temp. and forms a stabilized current, and hence nonuniformity is not caused even in the gas current shown by the arrow A2. In addition, even when the drawing stage proceeds and the preform 1 is shortened, the preform 1 and the pipe 6 are simultaneously moved by a slider 9, and an eddy current, etc., are not caused. |
