Practical distributed 3D hydro-acoustic localization technology for spatially heterogeneous response cables with adaptive multi-array fusion

Distributed optical fiber hydro-acoustic localization holds significant importance in underwater object detection, maritime security, and marine ecology monitoring. To address the practical challenge of spatial heterogeneity response of acoustic sensitive optical cable (ASOC), a practical distributed three-dimensional (3D) hydro-acoustic localization technology based on an adaptive multi-array fusion method is proposed in this paper. For the first time, Otsu’s method in the field of image processing is applied to the dynamic extraction of high response area of the cable. Multiple far-field detecting arrays are flexibly constructed in the digital domain with the standard far-field criterion, the azimuth conical surfaces of the target are obtained, a spatial spectral peak weight method (SSPW) is proposed for multi-array fusion and thus 3D target localization is realized. In the sea trial, four far-field arrays are constructed on a 93 m ASOC, enabling the 3D localization of a hydro-acoustic source with an average error of 6.53 m @220 m, representing a relative error of 2.97%, which verifies the feasibility of the proposed method. Further, repeated tests under varying conditions confirmed the robustness. This technology effectively solves the problem of harsh cable deployment requirements for hydro-acoustic target detection, and offers a practical distributed multi-dimensional localization method, potentially advancing the Ф-OTDR application in marine monitoring.