Miniaturized fiber Fabry-Pérot interferometer for strain sensing

A temperature-insensitive miniaturized all-fiber Fabry-Pérot interferometer strain sensor was proposed and experimentally studied. This sensor with an air cavity was made by splicing a short section of hollow-core fiber with two standard single mode fibers. The experimental results showed that these sensors have an fringe contrast exceeding 22 and 13 dB for the air cavity with a length of 167.08 and 557.11 μm, and its reflection spectrum shifts linearly to long wavelength by increasing the strain from 0 to 3000 με with a strain sensitivity of 1.8 and 1.7 pm/με, respectively. This strain sensor also showed good repeatability and long time stability, while its temperature sensitivity was only about 0.95 pm/°C in the range of 0°C-180°C for the 557.11 μm air cavity, so there is less strain-temperature cross-sensitivity. Moreover, this sensor was easy to be fabricated and there was no requirement for chemical etching, careful cleaving, and special fusion. It may be potentially used for strain sensing applications with high resolution and miniaturized size.