| 摘要 |
PURPOSE:To obtain an efficient small-sized optical directional coupler having simple constitution by diffracting an incident light or an exit light when this light passes an acoustooptic deflecting element. CONSTITUTION:The light emitted from a semiconductor laser LD is converted to parallel rays of light by a SELFOC lens SL and is made incident on a triangular prism PR at an angle psi2=78.6-90 deg.. Though this light is made incident on an acoustooptic deflecting element AOD after being refracted on a face 1, the element AOD is not driven by a signal source DR because a switch SW is turned off, and the incident light is made incident on a fiber FB to be measured through a lens LS1 as the light of the 0th order as it is. The light from the fiber FB is subjected to Fresnel reflection on the end face of the fiber and goes reverse in the fiber FB and is converted to parallel rays of light again by the lens LS1 and is made incident on the acoustooptic deflecting element AOD from the reverse direction. Since the element AOD is not driven yet, the light passes it as it is and is returned to the light source LD through the triangular prism PR.
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