| 摘要 |
PURPOSE:To obtain stable transmission characteristics without characteristic variations due to curvature, by sticking and setting a fused cladding material, made of metallic halide having lower refractivity than a bar-like material for a core has, around the material for the core. CONSTITUTION:In a long-sized container 4 to be inserted into a heating furnace 1, a cladding material 13, such as TlBr, made of alkali metal halide having lower refractivity and a lower fusion point than a bar-like material 12 for a core is contained. The container 4, after being held at a prescribed degree of vacuum by a vacuum device 9, is supplied with inert gas from a gas supply device 10 to form a prescribed gas atomosphere in it, thus setting an impurity-free state. The bar- like material 12 is dipped in a cladding material 13 and in this state, thermal supply from the heating furnance 1 is stopped to set the cladding material 13 covering the periphery of the bar-like material 12, thereby attaining adhesion to the bar-like material 12. Thus, infrared-ray optical fiber of good quality is obtained at low cost. |
