DAS Over Multimode Fibers With Reduced Fading by Coherent Averaging of Spatial Modes

We investigate the performance of distributed acoustic sensing over multi-mode fibers based on heterodyne phase-sensitive optical time-domain reflectometry. report a mathematical model describing relation between phase variation and applied strain in presence propagation that supports feasibility measurements fibers. also propose novel coherent averaging method achieves up to three-fold reduction noise floor compared state-of-the-art methods.