Temperature and Acoustic Impedance Simultaneous Sensing Based on FBS in Coated Optical Fiber

A novel method for simultaneous measurement of temperature and acoustic impedance based on forward Brillouin scattering (FBS) in a thin polyimide-coated G657 single-mode optical fiber is proposed. By measuring the changes of frequency shift and linewidth of the FBS spectrum corresponding to a certain transverse acoustic mode, temperature and acoustic impedance sensing can be realized with high sensitivity, high mechanical strength and relatively high accuracy. The linewidth-temperature, frequency shift-acoustic impedance and linewidth-acoustic impedance coefficients of the polyimide-coated fiber are 19.5, 5.5 and 5.9 times of those of the bare LEAF, respectively. In a proof-of-concept experiment, the thin polyimide-coated G657 is used as the sensing fiber, and the temperature and acoustic impedance measurement errors are 0.17 °C and 0.007 MRayl, respectively. The proposed FBS based sensor is expected to become a simple, accurate fiber sensor with potential advantages of durable and stable for simultaneously measuring temperature and acoustic impedance, which has great potential in many practical applications.