OPTICAL FIBER DRAWING METHOD AND DRAWING FURNACE

摘要

PURPOSE: To obtain an optical fiber drawing method capable of decreasing the fluctuations in the outside diameter of an optical fiber and an optical fiber drawing furnace capable of realizing this drawing method. CONSTITUTION: This optical fiber drawing furnace includes a furnace core tube 14 into which a preform 13 for the optical fiber is fed from an opening 23 at the top end and from the bottom end of which the optical fiber 22 is led out, an inert gas supplying means which passes an inert gas from the opening 23 at the top end of this furnace core tube 14 toward the bottom end, a heater 15 which encloses the bottom end of the preform 13 for the optical fiber across the furnace core tube 14 and melts this preform by heating, and a furnace body 12 which holds this heater 15 and the furnace core tube 14. The furnace core tube 14 has a cylindrical part 24 which exists upper than the position opposite to the part fused by heating of the preform 13 for the optical fiber and has a specified bore corresponding to the outside diameter size of the perform 13 for the optical fiber and tapered cylindrical parts 25, 26 which exist on the lower side of this cylindrical part 24 and have the bore made smaller nearer the lower side.