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

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.