Instantaneous frequency extraction of highly nonstationary optical interferometric signal using Reassigned Smoothed Pseudo Wigner Ville Distribution

Abstract

Instantaneous frequency (IF) of optical interferometric signal often carries information on various physical parameters such as velocity, strain and displacement. We propose smoothed Pseudo Wigner-Ville distribution method for extracting IF of highly non-stationary polynomial frequency modulated (FM) fringe signal. Cohen class signal representation is followed and time and frequency resolutions are independently optimized using separable kernel. Reassignment technique is further applied for sharpening of the spectrogram with these optimized kernels that improves accuracy in IF significantly. Quadratic FM along with strong nonlinear IF based fringe signal is considered for showing the efficacy of proposed method. Results are compared with that of existing Polynomial Wigner Ville Distribution method and Continuous Wavelet Transform (CWT) based approach and found to be more accurate in proposed technique. Finally fringe signal generated by varying the length of one of the legs of Michelson interferometer has been used to validate the proposed method experimentally.