| 摘要 |
PURPOSE:To manufacture a quartz glass tube having high strength and suitable as a raw material of an optical fiber, by heating a quartz glass tube at or above the softening temperature, and at the same time, reducing the environmental pressure, thereby removing the bubbles contained in the glass tube. CONSTITUTION:The quartz glass tube 1 is heated with the heating device 3 at a high temperature above the softening point, e.g. at 1,600-1,700 deg.C, and the environmental atmosphere 2 is evacuated with the vacuum pump 4, etc. to decrease the pressure. The small bubbles contained in the glass tube 1 are expanded by the procedure, and released from the glass tube by the large buoyant force of the bubbles. A quartz glass tube having high strength can be manufactured by this process. |
