Fiber Fabry-Perot Interferometer for Curvature Sensing

A curvature sensor based on a Fabry-Perot (FP) interferometer is proposed. A capillary silica tube is fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity lengths were developed and subjected to curvature and temperature. The FP sensor with longer cavity shows three distinct operating regions for curvature measurement. Namely, a linear response is shown for an intermediate curvature radius range, presenting a maximum sensitivity of 55.62 pm/m-1. When subjected to temperature, the sensing head produces a similar response for different curvature radius, with a sensitivity varying from 0.84 to 0.89 pm/˚C – this results in a small cross-sensitivity to temperature when the FP sensor is subjected to curvature. The FP cavity with shorter length presents low sensitivity to curvature.