Characterization of Distributed Brillouin Sensors Based on Elliptical-Core Two-Mode Fiber

Distributed Brillouin sensors based on the intramodal and intermodal stimulated Brillouin scattering (SBS) of the LP01 and LP11 guided modes in an elliptical-core two-mode fiber (e-core TMF) are investigated and characterized. The strain and temperature dependence of the Brillouin frequency (nu(B)) for each intramodal and intermodal SBS is measured, and the feasibility of distributed sensors based on the e-core TMF is tested. As an application of intermodal SBS, the Brillouin optical time-domain analysis with an LP01 mode probe and LP11 mode pump waves is demonstrated, which can simultaneously measure the distribution of nu(B) and the propagation loss of the LP11 mode. The strain and temperature coefficients of the double-peak Brillouin gain spectrum observed in the intramodal SBS of the LP01 mode are separately measured for each peak by applying a Brillouin optical correlation domain analysis with a differential measurement scheme. The experimental results show that e-core TMF can be used as a robust platform for distributed Brillouin sensors with strain and temperature coefficients of nu(B) in the intramodal and intermodal SBS very close to each other, with a discrepancy less than 1%.