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Quasi-distributed optical fiber sensors using multiple frequency shifters

Quasi-distributed optical fiber sensors using multiple frequency shifters (FSs) in two-mode elliptical core fiber (TMECF) are presented. Sensing measurand is the phase shift between the two propagating modes in the fiber. In the present experimental configuration, four FSs provide three independent sensing regions along a single TMECF. We construct one sensor in each region to measure localized strain and/or bending simultaneously. Cross talk among the sensors is theoretical and experimentally evaluated. Measurements were carried out using a computer system that allows a real time data acquisition and display.