Optomechanical fiber sensor for temperature and strain measurement based on broadband Brillouin amplification

Forward Brillouin scattering (FBS) in optical fibers is an optomechanical phenomenon that arises from photon-phonon interactions between optical waves and guided transverse acoustic modes. It has attracted increasing attention thanks to its ability to sense the surrounding environment. This mechanism enables multi-parameter measurements by leveraging the distinct responses (such as resonant frequency and linewidth variations across different acoustic modes) to ambient changes. Effective detection of FBS spectra, traditionally relies on fiber interferometers that convert acoustic-induced phase modulations into intensity signals. Although effective for demodulation, such methods suffer from two main limitations: the requirement of long fiber lengths (typically tens of meters) to accumulate sufficient phase modulation, as well as high optical power-based strong signal amplitudes to achieve adequate signal-to-noise ratios (SNR) for high-precision sensing. To overcome these challenges, we propose a broadband Brillouin amplification scheme that uses multiple Brillouin pump lines to amplify targeted different acoustic modes, enabling for high-precision simultaneous strain and temperature sensing in centimeter-scale along standard single mode fibers. Experimental results demonstrate that this scheme significantly enhances the SNR of weak FBS signals over a broader operating bandwidth, allowing high-precision dual-parameter measurements with minimum errors of 0.11°C for temperature and 25 με for strain.