Axial force analysis using half-etched FBG sensor

Abstract

Half etched fiber Bragg grating (HEFBG) is designed and studied by spectral properties under applied axial force. To design the HEFBG, a half-length of a given FBG is thinned down to 12μm diameter through the chemical corrosion with hydrofluoric acid. Under an applied axial force, the Bragg wavelengths due to etched and unetched parts of the HEFBG encounter different peak shifts and sensitivity. The peak-to-peak differences due to various axial forces are determined by analysing the spectral responses captured by an optical spectrum analyser (OSA). Theoretically and experimentally, it is observed that the peak-to-peak differences are a linear function of applied force. Using HEFBG as sensor probe, axial force sensitivity of 1.96 nm/N and resolution of 0.010 N are achieved over the range of applied force 0.20 N −2.50 N.