SNR improvement in time-expanded phase-sensitive OTDR using Nyquist zone averaging.

A recent advancement in distributed sensing known as the time-expanded phase-sensitive optical time-domain reflectometry (TE Φ-OTDR) addresses the trade-off between spatial resolution and detection bandwidth, enabling centimeter-scale resolution alongside RF detection bandwidth in the order of MHz. To date, TE Φ-OTDR approaches extract the fiber response from the first Nyquist zone (NZ). In this Letter, we propose a post-processing strategy to enhance the SNR by spectrally averaging different NZs. By evaluating 200 NZs, we have improved the average SNR of the traces by 23.56 dB compared to the standard demodulation scheme without degrading the acoustic sampling and the spatial resolution.