Study on XPM Phenomena in Single-Core Sensing System Integrated With OTDR and MZ-Sagnac Interferometer

To resolve the deficiency of distributed fiber optic interferometer (DFOI) in detecting static signals, a single-core composite fiber optic sensing system that integrates a Mach-Zehnder (MZ) Sagnac hybrid interferometer with an optical time domain reflectometry (OTDR) system using wavelength division multiplexing technology is presented in this paper. When continuous wave (CW) light from the interferometer and high-power pulses from OTDR propagate in one fiber core, pulses from OTDR deteriorate the performance of the interferometer due to cross-phase modulation (XPM) effect on CW light. This XPM effect induces nonlinear cross-talk in interferometric signals, which is analyzed with experimental validations. Furthermore, a Wiener filtering correction method is designed to suppress the cross-talk and improve the performance of the interferometer. In experimental validations, the location error of MZ-Sagnac interferometer influenced by nonlinear cross-talk could be reduced from 9471 m to 9 m averagely through the proposed Wiener filtering correction method. The single-core composite fiber optic sensing system corrected by Wiener filtering has broad prospects in practical engineering applications.