| 摘要 |
PURPOSE:To prevent the deposition of foreign material originated from a furnace core tube material on a preform during the drawing of a preform in a furnace core tube by inserting an upper and a lower quartz tubes concentrically into a furnace core tube and passing an inert gas between the quartz tube and the furnace core tube. CONSTITUTION:A quartz tube 2 is concentrically inserted into a carbon furnace core tube forming a gap of about 5mm along the inner wall of the furnace core tube 3 of a heating apparatus. The quartz tube 2 is divided into the upper section and the lower section to form a slit between both sections. An optical fiber preform 1 is inserted into the furnace of the heating furnace and an inert gas is passed through the gap between the inner wall of the furnace core tube 3 and the quartz tube 2 and blasted into the furnace through the slit between the sections. The preform 1 is heated with a carbon heater 4 through the furnace core tube 3 to effect the melting and drawing of the preform. The outer circumference of the preform 1 at the drawing part is maintained in an inert atmosphere together with the inner wall of the furnace core tube 3. Accordingly, the oxidation of the carbon material can be prevented to keep the preform 1 from the deposition of oxidized carbon fine particles. |
