Fiber optic sensor for hydrostatic pressure and temperature measurement in riverbanks monitoring

An optical fibre sensor for the simultaneous measurement of hydrostatic pressure and temperature in soil embankments is presented. It exploits the differential strain induced on a fibre in a dual-chamber case, constituting the sensor body. The strain, either induced by the pressure or by the temperature, is optically measured by means of coherent frequency domain reflectometry and variations induced by the two physical phenomena are discriminated because of the different behavior of the two chambers. Characterization of the sensor is presented and discussed. The prototype shows promising performance: temperature and pressure sensitivities are approximately -7 GHz/°C and -3.2 GHz/kPa respectively, with accuracies of 0.5 °C and 0.3 kPa.