METHOD FOR MANUFACTURING OPTICAL FIBER

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical fiber having good transmission loss characteristic by suppressing the fluctuation of the outer diameter of the optical fiber. SOLUTION: When melt spinning is performed by accommodating an optical fiber preform 2 in a furnace tube 11 of a spinning furnace 1 and heating the preform 2, the distance L1 of a clearance between the furnace tube 11 and the optical fiber preform 2 is set to be ≤25 mm, or the cross sectional area of the clearance is set to be ≤8,000 cm2. More preferably, the distance L1 of the clearance is set to be ≤25 mm, and the cross sectional area of the clearance is set to be ≤8,000 cm2. It is preferable that the distance L1 of the clearance is set to be ≥3 mm. This invention is effectively utilized when the inner diameter L2 of the furnace tube is ≥100 mm. COPYRIGHT: (C)2005,JPO&NCIPI