Design and finite element analysis of an elliptic-cylinder fiber optic structurally stable underwater mandrel hydrophone having composite foaming layer

Air-backed fiber optic mandrel hydrophones are being used in typical remotely interrogated phase interferometric sensor arrays for underwater acoustic surveillance applications. This paper is focused on the design of a new air-backed large-aperture composite mandrel hydrophone having a metallic inner tube and a composite foaming layer. A comprehensive set of hydrophone cases were selected and analyzed using finite element analysis (FEA) with varying geometric and material mechanical parameters. Using FEA, we evaluated strain distributions and natural frequency, computed pressure sensitivity and achieved optimum hydrophone configurations, having an omnidirectional directivity pattern. Its elliptic-cylinder streamlined shape with structural stability even up to 400 m depth of operation makes it well suited for submarine sonar flank arrays. The vital requirements of waterproof underwater packaging, customized fabrication details and the concept of easy array realization are also addressed.