Physics-Based Performance Optimization of Fiber Optic Interferometric Hydrophone with Push-Pull Mandrel Structure

The influence of the parameters of the elastic mandrel on the performance of fiber optic interferometric hydrophone with push-pull structure comprised of two concentric cylindrical shells is investigated through systematic solid mechanical analysis. The structural and material parameters considered include the Young's modulus, Poisson ratio, the thickness, length, and outer radius of the elastic tube. The result shows that a higher sensitivity of the push-pull fiber optic hydrophone can be obtained with a lower Young's modulus and Poisson ratio, and a thinner wall, larger radius, and longer length of the elastic tube, accompanied by a lower fundamental resonant frequency. Therefore, obtaining an optimal performance of the push-pull fiber optic hydrophone often entails a tradeoff between material properties and geometric parameters. A family of prototypical fiber optic hydrophones with different structural parameters are fabricated and examined experimentally, corroborating the results of solid mechanical (finite element method) analysis, among which the push-pull fiber optic hydrophone with the optimal parameters has demonstrated notably improved acoustic frequency response characteristics and a reduced minimum detectable pressure.