Photonic approach for precise and efficient distance measurement via utilization of multi-frequency broadband optical carrier-based microwave signal

Abstract

Distance measurement has received a growing demand with the development of scientific research and modern industry. However, most of the high-precision measure approaches hold stringent requirements on hardware equipment, manufacture accuracy, and operation environment. In this article, a photonic approach for distance measurement that utilizes broadband optical carrier-based microwave signal is proposed. Through switching between multiple modulation frequencies and applying the heterodyne process, a series of synthetic frequencies is constructed. Phase extraction is achieved based on all-phase fast Fourier transform (apFFT) for derivation of the distance. Moreover, we develop a phase unwrapping procedure to resolve phase ambiguity and derive the corresponding criterion for evaluation of reliability. The proposed method can realize tunable measurement range and high resolution within a relatively narrow bandwidth. Experiments verify the feasibility for distance measurement and align well with theoretical analysis. The results show good accuracy and stability with relative errors lower than 0.05%. Discussion demonstrates that apFFT is capable to suppress spectral leakage and mitigate the influence of signal truncation. As the presented approach maintains a simple configuration and competitive performance, it has great potential to become a useful tool for distance measurement in various practical applications.