A quasi-distributed optical fiber sensor

Abstract

Quasi-distributed optical fiber sensors using multiple frequency shifters (FS) in a two-mode elliptical core fiber (TMECF) are presented. The sensing measurand is the phase shift between the two propagating modes in the fiber. In the present experimental configuration, four FS provide three independent sensing regions along a single TMECF. The authors construct one sensor in each region to measure localized strain and/or bending simultaneously. Cross talk between the sensors is theoretically and experimentally evaluated. Measurements were carried out using a computer system that allows a real-time data acquisition and display. The measured strain and bending sensitivity for the TMECF used is Sstrain=(101+or-5) degree (phase shift)/m epsilon and Sbending=(0.75+or-0.01) degree (phase shift)/degree (bending). The cross talk between the sensors is around -20 dB.