Temperature and Axial Strain High-Accuracy Measurement Based on Forward-Brillouin-Scattering Direct Detection Structure

In this study, a novel temperature and axial strain simultaneous measurement method based on forward-Brillouin-scattering (FBS) direct detection structure is proposed and verified by experiments. The sensing mechanism exploits acousto-optic interactions that generate transverse acoustic waves through torsional-radial acoustic modes, which exhibit strong FBS signals and narrow spectral linewidths. By using the distinct temperature and axial strain dependencies of the FBS resonance peaks, two such modes are selected from the spectrum to form a sensitivity matrix, enabling decoupled dual-parameter measurement. Comparative experiments demonstrate that the proposed direct-detection scheme achieves superior measurement accuracy over the conventional Sagnac loop (SL) configuration, alongside a significantly simplified optical architecture. Experimental results validate the high performance of the system, achieving measurement uncertainties as low as 0.11 °C in temperature and 11 με in axial strain, derived from frequency shifts of the selected torsional–radial acoustic modes. The FBS direct detection structure, designed for simultaneous measurement of temperature and axial strain, holds broad application prospects in fields such as mechanical engineering, aerospace engineering, civil engineering, and environmental monitoring.