| 摘要 |
PURPOSE:To integrate effectively an optical by-pass circuit and make it small in size and inexpensive, by forming input and output ports for a multiple mode fiber and input and output ports for a light emitting element and a photodetector. CONSTITUTION:Two Fresnel zone plates F1 and F2 whose center positions are close to each other are formed on the rear face of a light-transmissive substrate S. These Fresnel zone plates F1 and F2 have the same optical characteristics to constitute a two-focus reflective focusing optical system. On the front face of the substrate S, first optical input/output ports M11, M22, M21, and M12 for up and down lines are positioned optically by Fresnel zone plates F1 and F2 and are provided, and second optical input/output ports R1, T1, R2, and T2 for a repeating circuit are provided as ports for up and down lines. The multi- mode optical signal is supported effectively by the two-focus reflective focusing optical system constituted of two Fresnel zone plates F1 and F2. |
