Discriminative strain and temperature sensing using a ring-hyperbolic tangent fiber sensor

Brillouin fiber sensors have demonstrated strong capability in discriminative and high-sensitivity multiparameter measurements. In this study, we proposed and numerically investigated novel ring core fiber-based stimulated Brillouin scattering for the simultaneous measurement of temperature and strain. The novel fiber, referred to as ring hyperbolic tangent (R-HTAN) fiber, is characterized by a shape parameter (α) that controls the optical refractive index and longitudinal acoustic velocity profiles. Numerical modal simulations indicated that the Brillouin gain spectrum contained multiple widely spaced and high-gain peaks, which were attributed to the strong interaction between the optical linearly polarized mode (i.e., LP_0,1 as a pump wave) and multiple high-order longitudinal acoustic modes. The designed R-HTAN fiber enabled the discriminative sensing of temperature and strain with levels that clearly surpassed values recently reported in the literature. In case of straight R-HTAN fiber (α = 0), the maximum C(α=0)T and C(α=0)ε are 1.928 MHz/ ^∘C and 0.087 MHz, respectively. In case of graded R-HTAN fiber (α = 1), the maximum C(α=1)T and C(α=1)ε are 1.872 MHz/ ^∘C and 0.0842 MHz/μɛ, respectively. The errors associated with temperature measurements (maximum δT_(α=0) = 0.0846 ^∘C and maximum δT_(α=1) = 7.4184 ^∘C) and strain measurements (maximum δɛ_(α=0) = 0.7250 μɛ and maximum δɛ_(α=1) = 7.4184 μɛ) demonstrated that the proposed fiber could be a promising candidate for next-generation Brillouin sensing systems for enabling temperature and strain discrimination.