Optical lock-in detection technique for coherent detection applications

摘要

An optical lock-in detection technique and circuit for coherent applications employing a photo-detector having a symmetric I-V curve is presented. The detection circuit includes a photo-detector operating as an optical lock-in amplifier, and a modulation source. The technique and circuit are used for coherent detection applications such as the determination of the frequency of modulation of an optical signal or the determination of the presence of an optical signal at a specified frequency. The technique and circuit are also used with one or more charge coupled devices in imaging applications.