Simultaneous measurement of temperature and pressure based on forward Brillouin scattering in double-coated optical fiber

A novel method for simultaneous measurement of temperature and pressure based on forward Brillouin scattering (FBS) in double-coated optical fiber is proposed. A new phenomenon, which is the linear relationship between frequency shift of the FBS spectra induced by radial acoustic modes and pressure surrounding the sensing fiber, is theoretically analyzed and experimentally verified. Another new interesting feature is observed that the frequency shift-pressure coefficients of different radial acoustic modes are different. Based on the phenomena that different radial acoustic modes have different frequency shift-temperature and frequency shift-pressure coefficients, we propose a brand-new method to achieve the simultaneous measurement of temperature and pressure by using the frequency shift information of two FBS scattering peaks. In a proof-of-concept experiment, a double-coated single-mode fiber is used as the sensing fiber, and the temperature and pressure measurement errors are 0.13 °C and 0.05 MPa, respectively. The proposed method is expected to become a simple, accurate, durable and stable sensing method for simultaneously measuring temperature and pressure, which has great potential in many practical applications.