| 摘要 |
PURPOSE:To carry out completely the hot fusion of a core glass rod to a clad glass rod and obtain a product of stable characteristics in the titled method for drawing the core glass rod placed in the clad glass rod while hot fusing both, by keeping the vacuum degree of a clearance between both within a specific range. CONSTITUTION:A core rod 1 having a smaller outside diameter than the inside diameter of a clad glass tube 2 is placed in the clad glass tube 2, and both are fed from above into a heating furnace 4 for spinning, softened by heat, fused, joined and drawn downward to mold a fiber 3 having a given outside diameter. The rod 1 is fused to a dummy rod 5 having about the same diameter as that of the rod 1, and the tube 2 is also fused to a dummy tube 6. Thus, the rod 1 and tube 2 are mounted to a holding tool 7 through the rod 5 and tube 6. In the process, the pressure of a clearance part 13 between the rods 1 and 5 and the tubes 2 and 6 is reduced to -100--600mm.Hg through a gas discharge channel 12 communicating to a tube mounting hole (7A) provided on the holding tool 7. |
