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 LP
₀₁
and LP
₁₁
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 (ν
_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 LP
₀₁
mode probe and LP
₁₁
mode pump waves is demonstrated, which can simultaneously measure the distribution of ν
_B
and the propagation loss of the LP
₁₁
mode. The strain and temperature coefficients of the double-peak Brillouin gain spectrum observed in the intramodal SBS of the LP
₁₁
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 ν
_B
in the intramodal and intermodal SBS very close to each other, with a discrepancy less than 1%.