Single-ended chaotic Brillouin dynamic grating based distributed decoupled measurement of temperature and strain

To address the practical limitations of conventional double-ended Brillouin dynamic grating (BDG) distributed fiber sensing systems, such as complex cabling, difficult data extraction, and loss of sensing upon fiber breakage, a single-ended chaotic BDG distributed fiber sensing system is proposed. In this system, two chaotic pump beams with a frequency difference are co-injected from the same end into the slow axis of a polarization-maintaining fiber (PMF) to interact and excite a chaotic BDG. A probe signal is simultaneously launched into the fast axis of the PMF, and both the temperature and the strain information are obtained by demodulating the Brillouin frequency shift (BFS) and birefringence frequency shift (bireFS). The generated chaotic BDG exhibits a single, stable and controllable profile, whose grating length is determined by the inherently short coherence length of the chaotic laser. Since all operations are performed from one fiber end, this proposed single-ended configuration enables independent generation and detection of the BDG while maintaining high spatial resolution, thereby achieving decoupled distributed measurements of temperature and strain. Experimental results demonstrate a spatial resolution of 2.0 cm over a 50 m sensing fiber, with temperature and strain measurement accuracies of 0.6 ℃ and 14 με, respectively.