Abstract
A new phase-reading detection method for signal processing in optical interferometric sensors is proposed and demonstrated. This method is based on a laser diode frequency modulated by a triangular waveform and time gating techniques. In our method, information on the optical phase can be extracted either from the beat frequency itself or the phase of the beat signal. The former would be used for displacement of the order of many wavelengths while the latter allows measurement in the subnanometer range. Detection of optical phase change as small as 2.0 × 10 -5 rad/√Hz with excellent linearity is demonstrated. Other useful applications of this technique are also briefly discussed.