Optical fiber preform, method of producing optical fiber preform, and glass rod for producing optical fiber preform

摘要

A method of producing an optical fiber preform by heating a glass preform that has a glass rod and a silica glass porous body and includes a valid portion and invalid portions, comprising: heating the glass preform while moving the glass preform along its axial direction relative to a heater; stopping the relative movement or decreasing a speed of the relative movement when an invalid portion positioned at a tail end reaches a vicinity of the heater; heating the invalid portion for a predetermined time while maintaining a temperature at which the silica glass porous body can be vitrified; decreasing the heating temperature to a temperature determined by adding 200°C to an annealing point of a silica glass; and removing the glass preform to the outside of the heating furnace without increasing the heating temperature to the temperature at which the silica glass porous body is vitrified.