Discrimination of temperature and strain by combined refractive index and birefringence measurements using coherent Rayleigh sensing

Abstract

Temperature and strain discrimination is experimentally demonstrated in an elliptical-core polarization-maintaining fiber by making use of Rayleigh-based distributed birefringence measurements and the frequency shift of the correlation peak obtained by standard coherent optical time-domain reflectometry. The high sensitivity of coherent Rayleigh sensing and the very distinct behavior of birefringence makes the two quantities clearly discriminated, resulting in temperature and strain accuracies of ~ 40 mK and ~ 0.5 με, respectively, for distributed measurements with a 2 m spatial resolution.

Fully distributed pressure sensing with ultra-high-sensitivity using side-hole fibers

“…Consequently, the phase change will turn into a FS in the RS spectrum and this FS can be estimated by cross correlating the current spectrum with a reference spectrum. Based on this technique, distributed birefringence (Bi) measurement was demonstrated [8], enabling the discrimination of temperature and strain by combining the distinct temperature and strain sensitivities along orthogonal polarization axes [9]. The interrogation scheme of Φ-OTDR is relatively simple, and there is no fundamental limit on sensing distance, making it potentially a good candidate for high-quality distributed sensing applications, for instance, for DPS.…”