| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method for an optical fiber preform that can suppress length-directional variation in external diameter of the optical fiber preform small.SOLUTION: In a process of drawing a transparent glass preform 9 comprising a core 7 and an inner layer clad 8, the external diameter of the transparent glass preform 9 is made continuously large in a length direction. In a process of obtaining a porous glass preform 17 which has a porous glass body 16 formed at an outer peripheral part of the transparent glass preform 9, the porous glass body 16 is so formed that glass fine particles are relatively large in deposition amount and bulk density on the side where the external diameter of the transparent glass preform 9 is large. In a process of sintering the porous glass body 16, a lower side of a second porous glass preform 17, having a small external diameter, of the transparent glass preform 9 is inserted first into a heating space of a heater while the porous glass preform is suspended and supported perpendicularly. |
