Multiplexed optical fibre strain sensing using cross-correlation of subcarrier interferometric spectra

A novel technique for evaluating strain in multiple long-length sections of optical fibre is described. Sections defined by reflective markers are interrogated with subcarrier interferometry. Path-length changes are monitored using cross-correlation. A resolution of 35 µm has been obtained over 5 m sensing sections, together with inter-section crosstalk levels below -45 dB.