| 摘要 |
PURPOSE:To manufacture a deformation-proof optical fiber having good dimensional accuracy by a procedure in which a raw material rod is inserted into a jacket tube and then the jacket tube is heated while applying a stress to the rod in the direction of the portion to be heated. CONSTITUTION:The raw material rod 1 is inserted concentrically into the jacket tube 2, and a ring heating element 3 to melt the jacket tube 2 is provided separately from and concentrically with the jacket tube 2. The jacket tube 2 is heated up to its softening and processing temperature (approx. 1,500-1,600 deg.C for quartz tube) by the ring heating element 3 while applying a stress (usually approx. 200g) to the rod 1 in the direction of the portion to be heated of the jacket tube 2, whereby an optical fiber raw material with good dimensional accuracy can be obtained while preventing the deforming move of the rod 1. Also, in case where the jacket tube 2 is evacuated by connecting a holder 5 to a vacuum pump 6, the deforming move of the rod 1 becomes noticeable usually but can be prevented by increasing a stress to apply to the rod 1 by the said method. |
