Weak coherent light interference heterodyne detection of transparent glass plate

We used a weak coherent light source with a central wavelength of 840 nm and a full width at half maximum (FWHM) of 25.429 nm to generate the weak coherent light. A 50:50 fiber coupler split the weak coherent light and directed it toward the optical delay line and simulated sample. A photodetector finally detected the optical signals. A transparent glass plate simulated the sample and generated the weak coherent interference heterodyne detector signal.