UWFBG Enhanced Distributed Dual-Parameter Sensing System Based on Laser Phase Noise Compensation and Variational Mode Decomposition

Traditional distributed optical fiber sensing (DOFS) systems are typically confined to single-parameter measurement. While incorporating multiple scattering mechanisms has emerged as a viable method for achieving multi-parameter sensing, challenges remain in developing cost-effective interrogation techniques that balance simplicity with high performance. In this work, we present an enhanced distributed dual-parameter sensing system integrated with variational mode decomposition (VMD) algorithm to decouple dynamic vibration signals from quasi-static strain and temperature variations. To enable full-channel laser phase noise compensation (LPNC), the system employs a combination of an auxiliary interferometer and an orthogonal chirp division multiplexing (OCDM) technique. The effectiveness of this LPNC–OCDM–VMD configuration is demonstrated through both experimental validation and numerical simulations. In the proof-of-concept experiments, the system achieves a vibration sensitivity of 0.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$p\epsilon/\sqrt{Hz}$</tex-math></inline-formula> in the 500-2500 Hz range and temperature resolution of 0.012°C over an 1100-m ultra-weak fiber Bragg grating (UWFBG) array with 20-m spacing. Notably, the proposed approach improves the signal-to-noise ratio (SNR) by more than 20 dB over the entire bandwidth compared with conventional phase-sensitive optical time domain reflectometry (ϕ-OTDR) interrogation using single-frequency pulses.