Distributed stress and temperature sensing based on Rayleigh scattering of low-coherence light

摘要

A novel arrangement for fiber optic distributed stress and temperature sensing based on the Rayleigh scattering spectra correlation method is proposed. The principal feature of the arrangement is usage of low-coherence light in probe pulses, which ensures a wide dynamic range for measurements at moderate sensitivity. Such a characteristic corresponds to performance specifications for infrastructure monitoring systems. A theory of optical time domain reflectometry for arbitrary coherence light is developed describing the contrast in reflectograms and Rayleigh scattering spectra properties. The experimental setup uses a wideband source of light pulses and an electronically controlled micro-electro-mechanical system optical filter for wavelength tuning. Temperature change experiments show root mean square (RMS) noise levels of 0.13 degrees C, 0.24 degrees C and 0.3 degrees C for fiber lengths of 2 km, 8 km and 25 km, respectively, at a spatial resolution of about 1 m (for 10 min data collection). As much as 2000 mu strain dynamic range is demonstrated in the stress measurement experiment while the noise level (RMS error) is estimated to be 2 mu strain. Our experimental results are compared with the theory and a satisfactory match is demonstrated.