Development of high performance distributed acoustic sensors based on Rayleigh backscattering

Distributed optical fiber sensing is a thriving research field that is finding practical applications in a variety of different fields including processes at extreme temperatures, security and civil engineering. The monitoring of dynamic perturbations, usually defined in the literature as distributed acoustic sensing (DAS), can be realized with excellent performance exploiting Rayleigh backscattering both in time and frequency domain. Devices implementing Rayleigh-based DAS are already commercially available. In this thesis the results of my three-year research are presented, reporting the development of high performance distributed acoustic sensors based on Rayleigh backscattering, and their applications. The research has focused on improving the spatial resolution of the chirped-pulse phase-sensitive optical time-domain reflectometer and on developing a novel algorithm to realize real distributed acoustic sensing with high spatial resolution and high acoustic bandwidth for the optical frequency-domain reflectometer (OFDR). Finally the early results of a measurement campaign performed in collaboration with the European Organization for Nuclear Research (CERN), where distributed optical fiber sensors were used to monitor superconducting lines and magnets, are presented and discussed.