| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical transmission tube which is widened in an opening angle (photodetecting angle), is reduced in the critical angle and is improved improve transmission performance. SOLUTION: The optical transmission tube having a transparent clad of a refractive index lower than the refractive index of a transparent solid core 1 around the core is constituted by forming a solid coating layer 2 so as to enclose the core, interposing an air layer 3 over substantially the entire length of the core between the core and the coating layer and forming the air layer 3 as a clad. The coating layer described above is formed of transparent material having the refractive index smaller than the refractive index of the core. |
