Process and apparatus for manufacturing a glass preform for optical fibres by drawing a preform

摘要

In the manufacture of a glass optical fiber preform with excellent accuracyof outer diameter, made by drawing an ingot of synthetic quartz to a rod, outer diameter measuring devices (67) and (68) measure the outer diameters at least at two positions (A,B) in the draw furnace, preferably that of the cone (2) (in the draw-down 3 one) and rod (3) drawn from the ingot (1), and the drawing speed is controlled based on the measured values. An apparatus for carrying out the method is also disclosed. Further disclosed is also an apparatus that finishes the rod into truly round form without any curve having rotary holding means (13) and (14) that hold the rod (3), resulting from the heating and drawing of the ingot (1), rotating it in synchronization with the rotation of the ingot (1), a comparison means (18) that outputs a signal after comparing the outer diameter of the cone (2) as measured by the outer diameter measuring device (11) with that of the referential circle, a control means (19) that controls the rotational amount of the rotating means (10), and a control means (20) that controls the rotational amount of the rotary holding means (13) and (14). <IMAGE>