Near-field target localisation based on the distributed acoustic sensing optical fibre in shallow water

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.