| 摘要 |
PURPOSE:To obtain an optical fiber having circular circumference, wherein at least a part of the core or the clad has a desired ellipticity, with a simple step, by evacuating the preform prepared by forming a thin glass film to the inner surface of a glass tube and melting the tube during the drawing process of the preform. CONSTITUTION:The cock 3 is opened and the cock 6 is closed, and the reaction gas is passed through the rotatably mounted glass tube 2 to the exhausting apparatus 9. During the above procedure, the heating burner 8 is transferred reciprocally along the tube 2 to form a thin glass film to the inner surface of the tube 2. The tube 2 is then molten to obtain a solid preform rod, which is heated and drawn to obtain an optical fiber. Prior to the melting of the tube 2, the cock 3 is closed, the outlet-side of the tube is molten and sealed, and the burner is moved slowly while introducing clean Ar gas, etc. to one opening of the T-branch attached to the inlet for the reaction gas and exhausting from the other opening to effect the evacuation of the tube 2. The tube 2 is heated and molten by this process to obtain a preform. The optical fiber obtained from the preform thus prepared is composed of a core 11, a clad 12, and a jacket 13 having elliptical circumference. |
