Expanding the sensing capabilities of forward Brillouin scattering in optical fibers by exploiting the differential response of radial and torsional-radial acoustic modes

The capabilities of optical fiber sensing based on forward Brillouin scattering (FBS) can be extended by exploiting the differential response to fiber perturbations of radial and torsional-radial acoustic modes. Radial and a subfamily of torsional-radial modes present a different sensitivity to changes of temperature and strain. By combining experimental measurements of the resonance frequencies of the different acoustic modes, we obtain (1) the Poison ratio of the optical fiber with an accuracy better than 1‰, and its temperature and strain responses, and (2), we demonstrate simultaneous and discriminative measurements of strain and temperature with accuracy better than 25 με and 0.2 °C, respectively.