| 摘要 |
PURPOSE:To keep the clearance between the outer diameter of an optical fiber preform and the inner diameter of an optical fiber preform insertion port at a desired value by adjusting the size of the insertion port of a drawing furnace in accordance with the difference from the outer diameter of the optical fiber preform. CONSTITUTION:The outer diameter of the optical fiber preform 3 is measured by an outer diameter measuring device 14 set directly above an inner diameter- variable upper seal 13 in the optical fiber producing device. The measurement signal is given to a controller 15, an upper seal driving mechanism 16 is driven under the guidance of the controller 15, and the inner diameter of the optical fiber preform insertion port 9 of the upper seal 13 is controlled in accordance with the inner diameter of the preform 3 to obtain a desired clearance. Consequently, the furnace pressure is kept constant at all times, the damage of the furnace is prevented, and the outer diameter of the optical fiber is stably uniformized over its entire length. |
