| 摘要 |
PURPOSE:To reduce insertion loss and to obtain uniform branching characteristics by composing an optical branching and coupling element of a branch-shaped internal layer which extends in the axial directions of pleural optical fibers and an external layer covering it, and decreasing the refractive index from the internal layer successively. CONSTITUTION:This element consists of the internal layer 13 which connects the optical fibers 10-12, an intermediate layer 14 formed at its outer periphery, an external layer 15 formed at the outer peripheries of the fibers 10-12, and matching layers 16-18 provided between the fibers 10-12 and layer 13. The refractive index of the layer 14 is between the refractive indexes of the layers 13 and 15. In this constitution, even if there is interface mismatching between the layers 13 and 14 and light is transmitted through the light 14, the light is reflected totally by the interface between the layers 14 and 15, so the light is propagated in the layer 13 again. Thus, the light loss is reduced. Further, the layers 16-18 are provided to reduce the coupling loss between the optical fibers and optical branching and coupling element and then reduce the light loss. Consequently, the uniformity of light output between output ports becomes superior. |
