A finite element analysis of an interferometric optical fiber hydrophone

This paper investigates the influence of structural parameters on the performance of an optical fiber wound mandrel hydrophone by using the finite element method (FEM). A hydrophone should exhibit the highest possible sensitivity, the widest possible flat frequency response, and an omni-directional sensitivity pattern within the frequency range. The parameters studied included the mandrel geometry, the thickness of the molding coated over the fiber, and the material properties of the constituent parts of the hydrophone. The analysis results showed that the pressure sensitivity of a hydrophone increases in relation to the length of the mandrel and the thickness of the molding. A higher pressure-sensitivity also requires a mandrel or molding material with a relatively low Young’s modulus and Poisson’s ratio. On the other hand, the flat frequency response of a hydrophone increases when either the mandrel length is shortened or the mandrel material is hardened. The omni-directional characteristic is also improved with a shorter mandrel. Therefore, a hydrophone with the best performance must balance the tradeoff between the geometrical and material parameters. The analysis discussion is focused on a representative specification of a frequency range of up to 5 kHz.