A method for distributed sensing of temperature, strain and weight formations employing the acoustic velocity and bulk modulus of fused silica

Abstract

This investigation presents a novel method for simultaneous measurements of temperature, strain and weight formations depending on Brillouin scattering mechanism exploiting the relations between these measurands and both the acoustic velocity and Bulk modulus of fused silica. To this end, a distributed sensing model has been constructed and the linear and polynomial equations related to the temperature and strain dependencies and sensitivities of acoustic velocity and Bulk modulus have been obtained. Furthermore, utilizing weights suspended at the end of the fiber in the sensing rig used in the model, strain formations occurring along the sensing fiber have been analyzed and second-order formula between strain and weight has been derived. Therefore, about 1 g change of the weight causes ~11 mu epsilon strain variation along the sensing fiber. For weight variations in the range of 0 - 1000 g, weight dependencies of the acoustic velocity and Bulk modulus have been achieved as 0.21 m/s (g)(-1) and 5.77 MPa (g)(-1), respectively. Moreover, weight sensitivities of the acoustic velocity and Bulk modulus in the same range of the weight variations have been computed as ~ -5.76 x 10(-7)%(g)(-1) and ~ -1.11 x 10(-6)%(g)(-1) for the spatial resolution of 1.55 m, respectively.