Weak Coherent Light Interference Heterodyne Detection Based on Time-Domain Signal Analysis

Abstract

Weak coherent light interference heterodyne detection is the theoretical basis for fiber optic gyroscopes, optical coherence tomography, and optical time-domain reflectometers. Classical statistical optics provides the signal model for weak coherent light interference. However, this theory does not describe signal acquisition and nonpolarization, which are significant in the analysis of heterodyne detection frequency, coherent length, and polarization mode dispersion (PMD). Consequently, it has difficulty solving signal processing problems related to coherent frequency and length analysis. This article proposed a time-domain signal analysis method. The approach can describe the practical signal acquisition and the polarized direction interference and accurately obtain coherent frequency and length on weak coherent light interference heterodyne detection signals by integrating the interference signals of monochromatic light within the linewidth of weak coherent light. We obtained the final mode of the signals using MATLAB. We established an experimental system to validate the practical value of the approach in signal processing. The average deviation between the experimental and theoretical coherent frequency and length is 120.6 Hz/0.48% and −0.0072 μm/−0.06%, respectively. Compared with existing theory, the proposed method is advantageous for describing detector acquisition and has practical value in heterodyne detection analysis. The proposed method can be widely applied to the systems based on weak coherent interference.