METHOD AND APPARATUS FOR DIRECT DETECTION OF SIGNALS FROM A DIFFERENTIAL DELAY HETERODYNE INTERFEROMETRIC SYSTEM

摘要

A direct detection method and apparatus for a fiber optic acoustic sensor array systems using an in line Michelson sensor TDM array and an interferometric section having two acousto-optic modulators that produce optical pulses that are frequency shifted with respect to each other. Direct detection is accomplished according to the equation: I(t) = A + B cos[f1 - f2 + 2p (f1 - f2) t], with the phase shift difference f1 - f2 between two paths containing the acoustic phase information and the frequency f1 - f2 being the difference between the RF frequencies for the two acousto-optic modulators.