| 摘要 |
PROBLEM TO BE SOLVED: To attain welding high in welding strength and without the inner diameter being decreased by chamfering the inner-diameter end of a dummy tube and/or a quartz glass tube on the welding face side before the quartz glass tube for an optical fiber preform is welded to the dummy tube and then welding both tubes. SOLUTION: A core glass rod for a preform is inserted into a quartz glass tube for the preform, heated and fused together. In this case, a dummy tube is connected since the quartz glass tube is expensive. An end of the dummy tube is welded to both ends of the quartz glass tube by an oxyhydrogen burner, a propane-oxygen burner or the like. The dummy tube with the inner diameter equal to or larger than that of the quartz glass tube and the wall thickness thinner than that of the quartz glass tube is used. The inner-diameter ends of both need to be chamfered when the inner diameters are identical, and only the smaller-inner-diameter tube is chamfered when the difference in inner diameter is large. Chamfering is preferably controlled to <=30% of the wall thickness of >=2 mm tube. A large-sized optical fiber preform is produced in this way. |
