| 摘要 |
PURPOSE:To suppress transmission loss and to permit easy working by coating a core with a coating material via the spacing intervened therebetween and making said spacing larger that the wavelength of the light to be used. CONSTITUTION:An optical fiber is formed of a core 10 consisting of a crystalline material and a coating material 11 consisting of a crystalline material having less absorption in the wavelength region to be used. The refractive index of the material 11 is lower than the refractive index of the core 10 and the core 10 is coated with a coating material 11 via a spacing 13 intervened therebetween, which spacing 13 is made larger than the wavelength of the light. A crystalline material such as thallium halide, silver halide or alkali halide is used for the core 10 and the clad 11. Such crystalline optical fiber is easily workable as the lower dimensional accuracy in working is allowed by the spacing 13 provided between the core 10 and the material 11. Since the coating 11 absorbs less light, there is substantially no absorption loss at the contact surface between the core 10 and the material 11 and the increase in the transmission loss is suppressed low even if the fiber is used bent. Measure for protection is made by providing a layer 12 having low light transmittability without spoiling the transmission characteristic. |
