Load Measurement Based on Forward Stimulated Brillouin Scattering in Photonic Crystal Fiber

We propose and demonstrate a novel optical fiber transverse load sensor based on forward stimulated Brillouin scattering (FSBS) in photonic crystal fiber (PCF), where a dual-wavelength Sagnac loop is employed for the activation and observation of FSBS. Due to the unique geometry of PCF that contains many air holes, transverse load that is applied to the PCF gives rise to the linewidth variations of the corresponding radial acoustic modes
$(\boldsymbol{R}_{0,m})$
induced FSBS spectrum. Highly linear dependence between the linewidth of specific
$\boldsymbol{R}_{0,m}$
induced FSBS spectrum and the applied transverse load has been experimentally verified. For proof of concept,
$\boldsymbol{R}_{0,5}$
acoustic mode induced FSBS spectrum is selected for measurement, and the calibrated linewidth linearity with respect to load is 1.7455 KHz/g. The proposed scheme shows immense potential for application in engineering measurements.