Geotechnical Effects on Fiber Optic Distributed Acoustic Sensing Performance

Distributed Acoustic Sensing (DAS) is a fiber optic sensing system used for vibration monitoring. This study investigates the effects that soil type, temperature, moisture content, time, and loading have on DAS performance. Impact testing was performed along a buried fiber optic array for over one year to induce a DAS response, which was evaluated using Signal-to-Noise Ratio (SNR). The results indicate that portions of the array in gravel consistently out-perform portions of the array in other soil types. Neither soil moisture nor temperature appear to have a significant effect on SNR. An increase in ground surface load was observed to increase SNR. A significant change in performance occurred while testing paused from March 2020 to August 2020 due to the Covid-19 pandemic. The observed changes highlight how DAS could be used for infrastructure monitoring, where such changes could possibly prompt a localized site inspection. Performance of a decade-old portion of the DAS array remained consistent and strong, suggesting that DAS has long-term viability.