OPTICAL FIBER DRAWING METHOD AND DRAWING FURNACE

摘要

PROBLEM TO BE SOLVED: To provide an optical fiber drawing method which is capable of suppressing the fluctuation in its diameter and a an optical fiber drawing furnace used for the same. SOLUTION: This optical fiber drawing furnace is provided with a furnace core tube 12 to which the preform 13 for the optical fiber is supplied, a carbon heater 15 which encloses this furnace core tube 12 and an upper chamber 20 which is connected to the top end of the furnace core tube 12 and houses the preform 13 for the optical fiber. The furnace described above has an auxiliary heater 25 which encloses a preform housing cylinder 21 and a heater moving device 33 which drives this auxiliary heater 25 to a heating position in proximity or contact with this preform housing cylinder 21 and a heat radiating position parting from the preform housing cylinder 21. Heat radiation is promoted without heating the preform housing cylinder 21 when the top end of the preform 13 for the optical fiber exists in the heating region in the upper part of the upper chamber 20.