SMFs With a Ge/F Co-Doped Inner Core for SBS-Based Discriminative Sensing of Temperature and Strain

Three-layered single mode fibers with a GeO
₂
and F co-doped inner core are proposed. Stimulated Brillouin scattering properties in the fibers are investigated for the discriminative sensing of strain and temperature. The optical properties of the proposed fibers are designed to be well compatible with those of the widely used standard single mode fibers. The acoustic properties, including effective acoustic velocity, Brillouin frequency shifts, and peak Brillouin gain efficiencies of the first three acoustic modes, are numerically calculated and elaborately analyzed under different structural and doping parameters. The co-doped fibers with three different structural and doping parameters are chosen for simultaneous sensing of temperature and strain because of their capability of supporting two comparable peaks, which can be easily identified and distinguished in the Brillouin gain spectrum. The sensing properties of the fibers are estimated and discussed. The temperature and strain sensitivities as well as the temperature and strain errors are calculated to be comparable to those of the few mode fibers and multimode fibers.