Subject of study. The paper presents the results of mathematical and experimental investigations of optical schemes for eliminating polarization fading in a coherent optical reflectometer. Aim of study. The aim is to increase the range and reduce the measurement error of the coherent reflectometer. In addition, its stability with respect to polarization fading, arising during the interference of a local oscillator signal and Rayleigh scattering, was improved by applying various coherent detection schemes. Method. For the theoretical investigation of various optical schemes of the receiving stage of a coherent reflectometer intended to eliminate polarization fading, a mathematical model was developed to estimate the average radiation power registered by the photodetector and its standard deviation under a random polarization state of the detected Rayleigh scattering. The selected scheme was experimentally verified using an operating prototype of the device. Main results. The results of mathematical modeling show that the scheme with polarization diversity using two polarization beam splitters and balanced photodetectors provides the highest efficiency in suppressing polarization fading. Experimental verification of the selected scheme in an operating coherent reflectometer shows that the polarization-diversity scheme effectively eliminates polarization fading and reduces the spread of the recorded reflectograms. Practical significance. The obtained results provide theoretical justification for the choice of an optical scheme for a coherent optical reflectometer. The results of the experimental investigation of the selected scheme demonstrate its effectiveness in eliminating polarization fading.
Ushanov et al. (2025) studied this question.