Static phase change in a fiber optic coil hydrophone.

For low acoustic frequencies, the acoustooptic interaction in a fiber optic interferometric coil hydrophone has been modeled on assumptions of hydrostatic and radial stress. However, an inherent ambiguity exists in the way by which the correct model has been chosen. It is established through unambiguous experimental determination of the sign of the induced static phase change that the hydrostatic model alone is valid. The method involves the use of a phase modulator constructed by bonding an optical fiber onto a piezoelectric PVF(2) film. Theoretical considerations which also favor the hydrostatic model are presented.