| 摘要 |
PURPOSE:To obtain an optical fiber material contg. small OH groups, by lining soot inside a quartz tube by the CVD method, blocking one end of the tube, and heating the tube with its inside pressure reduced. CONSTITUTION:Soot is lined on the inside of the quartz tube 1 by the CVD method, and one end 3a of the lined tube 2 is collapsed by heating it to form a blocked part 4 at the end of the tube 1. It is heated to remove water content, the inside is evacuated to make the inside pressure smaller than the outside one, and the side of the other end 3b of the lined tube 2 is blocked. Then, the tube 1 is collapsed by said pressure difference and by heating it with a heating source 7, such as a burner, moved in the arrow direction while leaving a gas holding part 6. Since this method allows no drying gas to pass through the tube, and prevents invasion of water, and since the pressure is controlled with the part 6, the obtained optical fiber material has small transmission loss. |
