Supersensitive sensors based on multicore optical fibres

In this work, we demonstrate the use of particularly characterised multicore optical fibres (MCFs) to devise compact, compellingly simple, ultrasensitive interferometric sensors which are capable of sensing single or multiple physical parameters. Generally, our devices operate in reflection mode and consist of a few centimetres of MCF fusion spliced to standard single-mode optical fibre (SMF). The tools and instrumentation needed to fabricate our devices are a conventional fibre cleaver and a fusion splicing machine. We demonstrate a highly-sensitive bending sensor (inclinometer) with a MCF with three strongly coupled cores which is capable of distinguishing multiple bending or inclination orientations, and also a force sensor based on MCF with seven coupled cores. In both cases the devices are interrogated with a low-power LED and a miniature spectrum analyser. Bending or force on the MCF induces drastic changes of the supermodes, their excitation, and consequently, on the reflected spectrum (interference pattern).