Extended, flexible, spatially weighted fiber optic interferometric

Abstract

A fiber optic hydrophone is formed as a single interferometer having widely separated interferometer segments formed in each of a pair of optical fibers. The interferometer segments are designed to allow averaging of the effects of local noise sources over a broad area in order to increase the acoustic signal-to-noise ratio. The interferometer segments also allow deployment of the hydrophone around sharp bends. A first optical fiber is formed into a plurality of spatially separated outer coils. A second optical fiber is formed into a plurality of inner coils corresponding to the outer coils. The inner and outer coils are preferably arranged in concentric pairs to form a plurality of sensor segments. A plurality of spacers is arranged such that a spacer is between successive sensor segments. The spacers are formed to guide the outer and inner optical fibers between successive sensor segments such that changes in the physical parameter between the sensor segments produce no phase difference between optical signals guided by the outer and inner fibers. The outer and inner coils are preferably arranged for exposure to the parameter such that changes in the parameter at each sensor segment produce opposite phase changes between the optical signals in the outer coils and the corresponding outer coil.