| 摘要 |
PURPOSE:To obtain the titled device for wiredrawing an optical fiber base material capable of uniformizing the outer diameter of the spun optical fiber and capable of obtaining an optical fiber having an excellent light transmission characteristic by almost uniformizing the area of the cross section at right angles to the wiredrawing direction of an annular clearance between the inner wall of a heating furnace and the optical fiber base material and the optical fiber. CONSTITUTION:The inner wall of a radiation cylinder 6 is funneled along the molten part from the optical fiber base material 4. The cross-sectional area at right angles to the wiredrawing direction of the clearance 13a between the base material 4 and the inner wall of the cylinder 6 at its upper end part, the clearance 13b between the molten part of the base material 4 and the inner wall of the cylinder 6 funneled after the molten part, and the clearance between the spun part of the optical fiber 12 and the inner wall 6 surrounding the fiber are almost equalized from the optical fiber base material inlet 5a to the outlet 5b. Consequently, the variations in the flow velocities of an inert gas due to the variations in the cross-sectional areas of the clearance parts 13a-13c are prevented, and the generation of the turbulent flow of the inert gas at the spinning part is prevented. Accordingly, the variance in the temp. distribution at the molten part of the base material 4 is prevented, and the optical fiber 12 having uniform outer diameter can be spun. |
