The distributed acoustic sensing optical fibre (DASF) is widely used for target detection and localisation on land as well as underwater optical fibre safety monitoring. To extend it to near-field target localisation in shallow water, DASF based on phase-sensitive optical time-domain reflectometry (Phi-OTDR) is used to receive near-field target signals. Given that the acoustic wavefront in the near field is spherical, the localisation method is based on the near-field localisation principle. The feasibility and accuracy of Phi-OTDR based on DASF for effectively locating near-field targets in shallow water are validated through simulations and practical experiments. Furthermore, the first experiment for applying DASF based on Phi-OTDR to near-field target localisation in shallow water is conducted, laying the theoretical and experimental groundwork for its improved application to un-derwater target detection.
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