Interference fading suppression for φ-OTDR based on non-uniform bandwidth allocation

Interference fading is a ubiquitous phenomenon in phase-sensitive optical time-domain reflectometry (φ-OTDR) fiber sensing systems. The spectrum extraction and remix (SERM) have been verified an effective approach to overcome this impairment. However, the conventional SERM usually uses equally spectrum slicing to improve the signal-to-noise ratio (SNR) and thus degrading the spatial resolution. In this paper, we propose an interference fading suppression scheme integrating non-uniform bandwidth allocation and non-dominated sorting genetic algorithm II (NSGA-II) multi-objective optimization. The proposed method adaptively tunes the extraction bandwidths for the main lobe and side lobe regions according to the energy distribution of probe pulses, thereby preserving effective signal energy while suppressing noise. Compared with traditional uniform-bandwidth SERM, the proposed method can achieve 3.57 dB to 8.37 dB improvement in SNR while maintaining the same spatial resolution without modifying the system architecture. The average standard deviation of differential phase is reduced from 0.218 rad to 0.045 rad, and interference fading is almost eliminated. This method effectively alleviates the inherent trade-off between SNR and spatial resolution in SERM and provides a practical solution for high-precision distributed acoustic sensing.