High-Resolution Simultaneous Measurement of Strain and Temperature Using π-Phase-Shifted FBG in Polarization Maintaining Fiber

We present a high-resolution simultaneous strain and temperature measurement scheme using π-phase-shifted fiber Bragg grating written in PANDA-type polarization maintaining fiber. Two optical parameters, the Bragg frequency and the birefringence-introduced frequency difference, are measured to perform the discrimination of strain and temperature. A double-sideband interrogation method together with a cross-feedback technique is introduced, which significantly reduces the measurement error in birefringence-introduced frequency difference, and hence improves the sensing resolution of strain and temperature. In the demonstration experiment, simultaneous measurement of strain and temperature with resolutions of 0.018 με and 0.0014 °C respectively is realized.