Abstract
We demonstrate simultaneous strain and temperature sensing based on hybrid Raman and Brillouin scattering with enhanced performance thanks to the combined use of standard Fabry-Perot lasers in conjunction with optical pulse coding techniques. The combination of both techniques allows for an improvement of ~8.7 dB in temperature resolution and ~3 dB in strain resolution, with respect to standard distributed feedback lasers, as confirmed by experiments, resulting in a final temperature / strain resolution of ~0.27K / ~30microepsilon over 25-km sensing fiber range, avoiding the use of optical amplification and wavelength averaging techniques.
Highlights
Optical-fiber distributed sensors provide a photonic-based enabling technology which encompasses a growing variety of applications, from structural-health monitoring, to leakage and deformation detection in pipelines, boreholes and power cables, from landslide warning to fire detection in reservoirs and tunnels [1]
For the hybrid sensing techniques that are based on combined Raman–Brillouin scattering, spontaneous Raman scattering (SpRS), which does not depend on strain, is exploited to directly infer the fiber temperature profile
This power level in narrowband sources is higher than nonlinear threshold level, allowing us to demonstrate the feasibility of using FP lasers with pulse coding to improve hybrid sensor performance
Summary
Optical-fiber distributed sensors provide a photonic-based enabling technology which encompasses a growing variety of applications, from structural-health monitoring, to leakage and deformation detection in pipelines, boreholes and power cables, from landslide warning to fire detection in reservoirs and tunnels [1]. A great part of distributed optical fiber sensors enables strain or temperature measurements. Those sensors allowing for simultaneous strain and temperature measurements are mostly based either on Brillouin scattering effect [2,3] or on combined Raman–Brillouin scattering effects [4], typically in conjunction with interrogating techniques based on optical time domain reflectometry (OTDR). For the hybrid sensing techniques that are based on combined Raman–Brillouin scattering, spontaneous Raman scattering (SpRS), which does not depend on strain, is exploited to directly infer the fiber temperature profile. In order to provide temperature-independent strain estimation, the temperature profile obtained from SpRS is used in BFS calibration
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