Real-time phase demodulation method for heterodyne Φ-OTDR using single-sideband spectrum interception and rotated-vector-sum

To meet the real-time requirements of phase-sensitive optical time-domain reflectometry (Φ-OTDR) applications in practical scenarios, accelerating the Rayleigh backscattering (RBS) phase demodulation is necessary. Here, we propose what we believe to be a novel phase demodulation scheme, single-sideband spectrum interception and rotated-vector-sum (SSB-SI-RVS). Theoretical analysis proves that this scheme can reduce the computational burden effectively, which is determined by the scaling factor, i.e., the ratio of the main lobe width to the RBS sampling frequency. In addition, this novel method has been implemented on a graphics processing unit (GPU) platform to realize real-time phase demodulation. The performance metrics of the proposed scheme, including signal-to-noise ratio (SNR), noise floor, and spatial resolution, were validated in the experiments. Meanwhile, the real-time rate of the proposed SSB-SI-RVS method exceeds theoretical requirements by 3.6 times. Finally, a series of tests confirms that the proposed method improves the average real-time rate by over 6.41 dB compared to other prevailing methods, i.e., digital I/Q and Hilbert transform, maintaining comparable key performance metrics. The method presented here provides a straightforward yet effective approach to realizing real-time Φ-OTDR to meet the practical requirements of on-site and long-term applications, such as downhole monitoring in the oil and gas industry.