Distributed sensor array and method using a pulsed signal source

Abstract

A distributed sensor system using pulsed optical signals optionally produced by a short coherence length source to provide a phase difference output signal representative of conditions affecting a selected sensor. In one preferred embodiment, an array of fiber-optic sensors are organized in a ladder configuration, with the sensors positioned in spaced relation and defining the rungs of the ladder. Light pulses transmitted through the sensors are multiplexed onto a return arm of the ladder. The multiplexed signals are received by an optical fiber compensating interferometer which coherently couples portions of adjacent multiplexed light signals to produce a phase difference signal representing conditions influencing selected sensors. In other preferred embodiments, the system is configured to define a plurality of adjacent Mach-Zehnder interferometers which provide output signal pairs which coherently couple to yield a phase difference signal directly representing the environmental effects on a particular sensor. Functional equivalents of the Mach-Zehnder interferometer configurations comprise configurations including adjacent Michelson interferometers. A phase and amplitude modulation technique is disclosed for providing heterodyned output signals from the distributed sensor system.