| 摘要 |
PURPOSE:To detect immediately the occurrence of disconnection in the light incidence side, by propagating the scattered light, which is reflected at a breaking point when an optical fiber is broken, to the light incidence side while reflecting this light on the boundary face between the first clad layer and the second clad layer and detecting the light. CONSTITUTION:An optical fiber 1 consists of a center core 2 having a refractive index n1, the first clad layer 3 having a refractive index n2, the second clad layer having a refractive index n3, and a protection coating layer 5, and n1> n2>n3 is satisfied. The light from a light source 6 is made incident to the center core 2 of the optical fiber 1 and is propagated to the light exit side. If the optical fiber 1 is broken on the way, the light propagated in the center core 2 is subjected to Fresnel reflection at a breaking point 10, and the scattered light is propagated to the light incidence side while being reflected on the boundary face between clad layer 3 and 4 and is detected in the position of a notched part 9 by a photodetector 8. |
