| 摘要 |
PURPOSE:To make the production of an intended base material for optical fibers possible in the stage of production of a base raw material for optical fibers that generates double refraction in the core part by forming a thin film of glass on the inside wall of a quartz glass tube then reducing the pressure in the tube down to the pressure below the atmospheric pressure and melt sticking the tube by heating thereby making the tube solid. CONSTITUTION:A quartz glass tube 1 of 5-50mm. outside diameter and 0.3-5mm. thickness is prepared as a base material 1 for optical fibers, and a thin film 2 of glass for formation of the clad of optical fibers and a thin film 3 of glass for formation of the core are formed by a chemical deposition method on the inside wall of said tube. Silica glass contg. B2O3 of a softening point lower than that of the softening point of quartz glass is used for the film 2 and glass of a softening point higher than that of the film 2 is used for the film 3. Such tube is heated with a burner 4 to melt stick the end part, after which the inside is evacuated and the burner 4 is moved to make the tube solid with the films 2, 3, whereby the tube is formed to the base material having an elliptical shape in section wherein the outside circumference attains C2/a>=200/(100-r)-1 where the rate of ellipse is r, the minor axis diameter of the elliptical shape C2 and the diameter of the core formed a. |
