High Spatial Resolution Sensing of Temperature and Strain Without Cross Sensitivity Based on Chaotic Brillouin Dynamic Grating

A distributed fiber-optic sensing system based on chaotic Brillouin dynamic grating (BDG) without cross sensitivity of temperature and strain is proposed and experimentally demonstrated. The chaotic BDG is stimulated by interaction of two chaotic pump beams with a certain frequency difference along the slow axis of polarization-maintaining fiber (PMF) and detected by the continuous probe light along the fast axis. The generated chaotic BDG has the characteristic of single, permanent, and localized grating. The grating length is determined by the low-coherence length of the chaotic laser, which ensures that the spatial resolution of the chaotic BDG sensing system can reach the centimeter scale. Two parameters, i.e., Brillouin frequency shift (BFS) and birefringence frequency shift (BireFS), are measured to achieve the temperature and strain simultaneous discrimination. In the experiment, a 2.3-cm spatial resolution noncross-sensitivity measurement was demonstrated over a 100-m long PMF, where temperature and strain discriminative accuracy can reach 0.3 °C and $11 \mu \varepsilon $ , respectively.