FURNACE FOR MANUFACTURING OPTICAL FIBER WITH DIFFERENT INLET AND OUTLET DIAMETERS

摘要

PURPOSE: A furnace for manufacturing optical fiber is provided to prevent oxidation and impurity formation of the surface of optical fibers by using a muffle tube having different inlet and outlet diameters which induce the smooth flow of inert gas in heating of optical fiber preform. CONSTITUTION: The furnace for optical fibers comprises the parts of: a furnace shell with an inlet and an outlet to which an optical fiber preform tube(100) is pierced; a graphite heating element(11) placed around the preform tube; an electrode close to the ends of heating elements; a rigid insulation canister(13), made of graphite felt, placed between graphite heating elements and shell; a muffle tube forming sleeves(15, 15') inducing inert gas to flow to the heating part for preventing the inside of the furnace from oxidizing, wherein the muffle, whose diameter at the furnace inlet is smaller than that at the furnace outlet, is inserted into a hollow of the heating element and the preform tube is passed through the muffle tube; a first flow passage(21) where the inert gas flows into an outer space of the heating element from the outside; a second flow passage(22) where the inert gas flown through the first passage flows to an inner space of the heating element; a third flow passage(23), placed between heating element and muffle tube, where the inert gas is flown into the inside of the heating element.