| 摘要 |
PROBLEM TO BE SOLVED: To produce a silica glass preform for a transparent vitrified fiber in a single process by a powder shaping method without needing a porous-body- producing process, a dehydrating and transparently vitrifying process and a few other processes. SOLUTION: This is a method for producing a preform 9 for an optical fiber by forming clad layers on the peripheries of a single or plural cores, etc. In the method, one or plural silica glass bars 2 for forming cores, etc., are inserted into an outer cylinder 1 made of silica glass, and a powdery material mainly containing silica is filled between the outer cylinder 1 and the silica glass bars 2 to form a silica-powder-filled body 10. The silica-powder-filled body 10 is serially heated and fused in the direction of the shaft by zone fusing while keeping a powder-body-filled region in a reduced pressure atmosphere, and the fused material is drawn to produce the objective preform 9 for an optical fiber. |
