APPARATUS FOR DRAWING OPTICAL FIBER PREFORM AND DRAWING USING THE SAME

摘要

PROBLEM TO BE SOLVED: To reduce the variation width of the diameter of the final gap in drawing an optical fiber preform of a large diameter (ingot) into an optical fiber preform of a small diameter. SOLUTION: This drawing apparatus sends an optical fiber preform (ingot) G of large diameter from the upper part to the lower part by an ingot feed mechanism 1, heats the preform by heaters 4 of plural vertical steps of a lower electric furnace 2 and takes-off the preform by a pulling mechanism 3 to produce an optical fiber preform P of small diameter. In this case, the height of the heater 4 at the lowest step is made shorter than the other heaters 4 and a gap is lessened so that a part required to draw is concentrically heated and parts except that part are not affected by a thermal influence.