| 摘要 |
PURPOSE:To obtain the titled preform easily and continuously, by intermittently controlling the deposition of glass soot for stress-imparting part and the deposition of glass soot for clad, thereby alternately forming the preform for stress- imparting part and the preform for clad. CONSTITUTION:A preform 30 for core is formed at one end of a rotating supporting rod by VAD process, and a preform 32 for an intermediate layer is formed to the circumference of the core preform. Thereafter, the glass soot for the stress-imparting part and the glass soot for the clad are deposited on the preform 32 for the intermediate layer using the torch 26 for the stress-imparting part and the torch 28 for the clad. Both torches are placed on the same plane perpendicular to the axis of the supporting rod making a definite angle (e.g. 90 deg.) to the axis of the supporting rod. The deposition of the soot is paused intermittently during the one revolution of the supporting rod in a manner to deposit the glass soot having the same composition to the parts symmetrical around the supporting rod. The preforms 36A, 36B for the stress-imparting part and the preforms 38A, 38B for the clad are formed alternately. |
