Multiplexed optical fibre Fabry-Perot sensors for strain metrology

The authors demonstrate that several optical fiber Fabry-Perot sensors can be multiplexed in series for axial strain monitoring at each individual sensor. White light interferometry was employed using the laser-referenced Michelson interferometer of a standard Fourier transform spectrometer as a receiving (interrogating) interferometer. The primary aim was to demonstrate that at least six fibre Fabry-Perot transducer interferometers (sensors) can be multiplexed in series provided that each sensor has a unique optical cavity length within the multiplex. The resulting differing optical path differences at each fibre Fabry-Perot sensor give rise to sharp correlation features (side-bursts) at unique positions in the time domain as observed in the interferogram. An optical cavity length change due to an axial strain perturbation is observed as a change in the position in the time-domain of the side-burst feature associated with the fibre Fabry-Perot sensor. This paper demonstrates that multiplexed strain metrology in the quasi-static regime using fibre Fabry-Perot sensors is possible with a measurement range of typically 0 to 4000 microstrain and a strain resolution of better than 10 microstrain.