The sensor is constructed so this path difference is a sensitive function of the measurand of interest. In the case of a fiber optic hydrophone, the sensor is constructed so this path length difference is affected by acoustic pressure. The sensor output, is therefore an intensity which depends sinusoidally on the measurand. This intensity output is transmitted back to the dry end of the system, where an electronic demodulator linearizes it, producing a voltage proportional to the interferometer fringe phase. General Description Litton can produce arrays of fiber-optic acoustic sensors for a variety of applications.
Arrays can contain hundreds of channels.
They are configured as planar arrays molded to be conformal with any desired mounting platform, or as linear arrays in hoses or thinline cables that can be reeled over small diameter winches. Present arrays are configured primarily for underwater hydrophones. Fiber optic geophones and accelerometers are employed in land-based systems and some marine sea floor applications. The arrays themselves comprise only passive fiber-optic elements, and contain no electronics. The data are transmitted on a few single mode fibers, over distances of up to several tens of kilometers.