Dual-parameter fiber sensor based on mode-division demultiplexing BOTDR system

We present and experimentally validate a neoteric and cost-effective dual-parameter distributed fiber sensor based on a Brillouin optical time-domain reflectometry in a general four-mode graded-index few-mode fiber. The spontaneous Brillouin scattering signals of different modes in the sensing fiber can be obtained simultaneously by a low-loss mode selective photonic lantern, on account of the difference of mode refractive indexes of different modes. By characterizing and evaluating the Brillouin scattering spectrum widths and the Brillouin frequency shift to temperature and strain sensitivities of different modes, the performance of the dual-parameter distributed sensor can be optimized. The proposed sensor achieves reliable differentiation of temperature and strain on a 1 km general four-mode graded-index few-mode fiber, with the temperature and strain accuracy of 1.6 °C and 39.2 με, respectively.