Combined Sagnac and intermodal interferences for discrimination of strain and temperature variations

A fiber sensor capable of discriminating the strain and temperature variations is presented and fully investigated. Its simple configuration is a Sagnac interferometer containing only one piece of high birefringence few-mode fiber and a polarization controller in the loop arm. The Sagnac and intermodal interferences are generated simultaneously. Based on the combined interferences, it is possible to decouple the strain and temperature changes by monitoring the wavelength and power of one localized peak originating from the intermodal interference in the spectral response of the Sagnac interferometer.