| 摘要 |
PURPOSE:To produce the optical fiber which has a long life and less losses by combining a high-purity carbon core tube coated with a gas impermeable film and a pressing mechanism so as to exhibit a specific effect. CONSTITUTION:A porous glass base material 1 is mounted to a rotatable and vertically movable shaft 2 and a heating element 4 made of carbon, etc., is provided in an electric furnace 3. The carbon furnace core tube 5 internally inserted into the furnace 3 consists of an upper cap 14 and a cylindrical part 15 and the surface thereof is coated with SiC. The cylindrical part 15 of the core tube 5 is divided, from the upper part, to 15-1, 15-2, 15-3, 15-4, 15-5 and a gas supply port 6 supplies gas to the core tube 5. The cylindrical part 15 of the furnace core tube is fixed to the flange part of 15-1 by a support 7 and the 15-5 part is pressed by a plate 6 and an air cylinder 9. Since the plate 8 and the air cylinder 9 are in point contact with each other, the axial pressing force of the core tube 5 is uniform in the circumferential direction. An air pressure is supplied via a reducing valve 10, a valve 11, a speed controller 12, an air reservoir 13 to the air cylinder 9.
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