Description
Among the different fiber optic techniques, Rayleigh-based distributed fiber optic sensing offers unmatched spatial resolution and accuracy. With its sub-centimeter spatial resolution and microstrain accuracy over tens of meters, this technology is ideal for precise monitoring in geotechnical and civil engineering applications.
This technique utilizes Rayleigh scattering to track environmental effects on light propagation, and the measurement is done through the spectral correlation analysis of the so-called Rayleigh signature, which is specific to each fiber and can be accounted for to track variation in the light propagation due to the environment. A first measurement of the Rayleigh signature is kept at the beginning of the monitoring campaign, and it is then used as a reference to determine the change in the strain or temperature field affecting the fiber. Still, so far, for installation where fibers were employed in harsh conditions, it has been shown only in quite favorable conditions, i.e., by using the same specific device and setup and over a short time
In this work, we investigate the enduring presence of Rayleigh's signature in optical sensing fibers installed in challenging environments. Our study demonstrates that measurements obtained from optical fibers used in adverse conditions, such as within a foundation pile and soil anchors in an unstable slope, continue to exhibit a Rayleigh signature correlating to the reference one, even after a period exceeding five years since the initial measurements were taken, and using different interrogators and setups.