Efficient Phase Demodulation of Optical Carrier-Based Microwave Interferometry for High-Precision Dynamic Distance Measurement

We propose a technique to achieve high-speed and high-precision distance measurement via phase demodulation of broadband optical carrier-based microwave interferometry (OCMI). An in-phase and quadrature (I/Q) processing scheme is designed and incorporated to measure the phase shift induced by target distance. The results could be efficiently derived from a minimum of one pair of detected outputs with immunity to power fluctuations. To extend the non-ambiguous measurement range while maintaining high resolution, a multifrequency-based phase unwrapping procedure is implemented. In the meantime, a driving module is utilized to effectively amplify and stabilize the signal. Experiments were carried out to evaluate the feasibility and performance of the proposed OCMI distance measurement method, which exhibits good accuracy, stability, and reliability. The maximum residual error is found to be 0.084 mm and the relative error is less than 2 × 10
⁻⁴
. Moreover, the method is capable to perform thousands of measurements within a few seconds, thus the OCMI-based dynamic target tracking has been achieved.