Simultaneous optical fibre strain and temperature measurements in a hybrid distributed sensor based on Rayleigh and Raman scattering

A new type of sensor for simultaneous measurements of strain and temperature changes in an optical fibre is proposed. Its operation builds on the use of Raman optical time-domain reflectometry and wavelength-tunable quasi-monochromatic Rayleigh reflectometry implemented using a microelectromechanical filter (MEMS). The sensor configuration includes independent Raman and Rayleigh scattering channels. Our experiments have demonstrated that, at a sensing fibre length near 8 km, spatial resolution of 1 - 2 m, and measurement time of 10 min, the noise level (standard deviation) is 1.1 μϵ (μm m−1) for the measured tension change (at small temperature deviations) and 0.04 °C for the measured temperature change, which allows for effective sensing of mechanical and temperature influences with improved accuracy.