Discrimination of strain and temperature sensitivities based on temperature dependence of birefringence in long-period fiber gratings

Abstract

We experimentally demonstrate the simultaneous measurements of strain and temperature on the basis of the temperature dependence of birefringence in a long-period fiber grating (LPFG) fabricated with a birefringent fiber. Birefringence induces dual peak formation in LPFG corresponding to the grating's polarization state. Depending on the temperature sensitivity of birefringence in LPFG, the differences in the wavelength shift and wavelength spacing change of dual peaks with variations in strain and temperature allow accurate and simultaneous measurements of strain and temperature, respectively. The rms errors of the measured strain and temperature were 7.5 mu strain and 0.5 degrees C, respectively.