Predicted Performance of a Heterodyne Detector with a Fiber Optic Coil Hydrophone

In recent years, much attention has been focused on the application of fiber optics to underwater acoustic detection. In this regard, a hydrophone may be constructed of coiled optical fiber. Ultimately, it would be desirable to have only fiber optic elements and cables in the wet end of a towed array system. However, lead fibers are also susceptible to acoustic modulation, introducing grave ambiguities in the detection process. In this paper, a heterodyne detection system, devised at General Electric, which will eliminate the problems associated with stray signals induced in the lead fibers, is analyzed for use in a towed array.