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Distributed optical fiber sensors with the capability of dynamic temperature and strain discrimination can be used for various applications, including perimeter security, structural health monitoring, and seismic sensing, as they can access the tolerance of the structures and sites to natural hazards, such as earthquakes, fires, and overflows. Here, we propose a hybrid Brillouin/Rayleigh sensing system that combines distributed phase matching measurement via Brillouin dynamic grating and inhomogeneity-induced Rayleigh scatting in polarization-maintaining fiber. Due to the high birefringence of polarization-maintaining fibers imposed by the stress-rods, the detection of Brillouin dynamic gratings results in opposite signs of spectral shifts under the changed temperature and strain, giving a high discrimination accuracy. In addition, the usage of a single chirped probe pulse signal allows a single end detection system for Rayleigh of the probe wave and idler wave from stimulated Brillouin scattering enhanced four-wave mixing, which simplified the sensing system significantly. Driven by the high spatial resolution ability of distributed phase matching measurement without phonon lifetime limitation, an intensity-based analysis approach for Rayleigh traces is carried out to resolve the external perturbation applied in a short section that is smaller than the spatial distinctness associated pulse width. In the proof-of-concept experiments, a simultaneous strain and temperature variation within a 40 cm fiber section are successfully discriminated with noise equivalent discrimination errors for strain and temperature of 112.2 nɛ and 10.9 m °C. The spatial resolution here is 2 m, and the maximum system’s sampling rate is up to 100 kHz without average, corresponding to the sensing distance of 1 km.
Wang et al. (Tue,) studied this question.