METHODS FOR PRODUCING OPTICAL FIBER AND PREFORM

摘要

Methods for producing an optical fiber and a preform in which a composite matrix formed by inserting a core rod into a quartz glass tube for clad is placed in the vertical direction and the lower end part thereof is thermally fused and dripped to integrate the core rod and the quartz glass tube and to start drawing, characterized in that the quartz glass tube and the core rod are secured while aligning the lower end part with the quartz glass tube and in that the outer circumference and inner circumference of the lower end part of the quartz glass tube are circular, the outside diameter is tapered, as a whole, toward its tip, the amount of misalignment of the center of the circle of the average outside diameter of the circular cross sections of the tapered portion with the straight body section of the quartz glass tube is not larger than 1% of the outside diameter of the straight body section, and the difference between the maximum thickness and minimum thickness of each circular cross section is not larger than 1.5% of the average thickness, and such a quartz glass tube is used.