A frequency-modulated-continuous-wave laser detection system based on the four-quadrant photodetector

A frequency-modulated-continuous-wave (FMCW) laser detection system based on the four-quadrant photodetector was presented in this paper. The cross-power-spectral-density (CPSD) algorithm was introduced to remove the incoherent noise in the four-quadrant signal spectrums. Some traditional denoising methods, including the empirical mode decomposition direct wavelet thresholding method, EMD interval thresholding method, correlation-based EMD partial reconstruction, fast Fourier transform and wavelet transformation, were investigated to provide a comparison with the CPSD algorithm. Both the simulation and experiment results show a superior performance of the four-quadrant detection system using CPSD algorithm. A better signal-to-noise ratio of the target echo to smoke interference was obviously increased to 6.3 dB under the smoke interference conditions. The relative error of this detection system was reduced from 7.36 to 1.36% , and its absolute error was less than 0.15 m. Therefore, this study was helpful in improving anti-interference ability of FMCW laser detection system.