| 摘要 |
PURPOSE:To suppress the formation of bubbles by heating and degassing a purified powder formed body in vacuum, exposing the body to He gas to impregnate the body with He and then sintering the body in an atmosphere contg. He. CONSTITUTION:The Sin2 powder having <=1 mum particle diameter as the starting material is hydrostatically formed into a powder formed body of specified shape. The body is heat-treated in a Cl2 atmosphere to remove water and impurities and purified. The powder formed body (soot 6) is set in a furnace core tube 7, a gas treating furnace 8 is heated, a shutter 10 is closed, and the tube is evacuated to a high vacuum from an exhaust valve 11. He is then introduced from a first gas inlet 12 to fill the soot 6 with He, the shutter 10 is opened, and the supply of He from the inlet 12 is stopped. Subsequently, He is introduced from a second gas inlet 13, the soot 6 is slowly lowered into a sintering furnace 9 at a specified temp. and sintered, and an optical fiber preform free of bubbles is obtained. |
