SHUTTER DEVICE OF HEATING FURNACE OF OPTICAL FIBER PREFORM

摘要

PURPOSE: To produce an optical fiber preform having high quality by suppressing the infiltration of air as far as possible at the time of carrying out an operation to make the fiber transparent. CONSTITUTION: This shutter device has first shutters 2 which close the apertures on both top and bottom ends of a heating furnace 1 and second shutters 3 which are disposed on the side outer than these first shutters 2. The apertures on both top and bottom ends of the heating furnace 1 are closed by the first shutters 2 and the second shutters 3 are closed in the state of holding the first shutters 2 open in the heating furnace 1 in which the air is substituted with an inert gas at the time of substituting the air filled 10 the heating furnace 1 with the specific inert gas prior to the heating operation of the furnace 1.