A FINITE-ELEMENT ANALYSIS OF AN INTERFEROMETRIC OPTICAL-FIBER HYDROPHONE

This paper investigates the influence of structural parameters on the performance of an optical tiber wound mandrel hydrophone by using the finite element method (FEM). A hydrophone should exhibit the highest p ossible sensitivity, the widest possible flat frequency response, and an omni-directional sensitivity pattern within the frequency range. Th e parameters studied included the mandrel geometry, the thickness of t he molding coated over the fiber, and the material properties of the c onstituent parts of the hydrophone. The analysis results showed that t he pressure sensitivity of a hydrophone increases in relation to the l ength of the mandrel and the thickness of the molding. A higher pressu re-sensitivity also requires a mandrel or molding material with a rela tively low Young's modulus and Poisson's ratio. On the other hand, the flat frequency response of a hydrophone increases when either the man drel length is shortened or the mandrel material is hardened. The omni -directional characteristic is also improved with a shorter mandrel. T herefore, a hydrophone with the best performance must balance the trad eoff between the geometrical and material parameters. The analysis dis cussion is focused on a representative specification of a frequency ra nge of up to 5 kHz. (C) 1998 Acoustical Society of America.