High accuracy pressure and temperature simultaneous measurement based on forward Brillouin scattering in highly nonlinear fiber

An original method for high accuracy pressure and temperature simultaneous sensing is proposed, which is based on forward Brillouin scattering (FBS) spectra induced by high-order radial and torsional-radial acoustic modes in highly nonlinear fiber (HNLF). Firstly, a novel method for selecting suitable sensing fiber with a high FBS gain coefficient is proposed, and an HNLF is selected for high accuracy sensing, where the FBS spectra induced by high-order torsional-radial and radial acoustic modes have high sensitivities while maintaining relatively high signal-to-noise ratios. The frequency shifts of the FBS spectra induced by two types of acoustic modes are linearly related to pressure and temperature, and different acoustic modes have different frequency shift coefficients. Then, based on these new characteristics, we propose a simultaneous pressure and temperature measurement method based on FBS spectra induced by high-order radial and torsional-radial acoustic modes. In a proof-of-concept experiment, the high measurement accuracy is achieved with low measurement uncertainties of 0.08 MPa for pressure and 0.07 °C for temperature. The proposed method of using FBS spectra induced by high-order radial and torsional-radial acoustic modes provides a new perspective for high-precision multi-parameter measurement.