Calibration of fiber optic strain sensors

The raw measurement signals of fiber optic sensors are typically phase changes (interferometric sensors), wavelength shifts (FBG sensors) or frequency shifts (Brillouin sensors). For strain based monitoring these raw measurement values have to converted into strain changes using appropriate conversion functions with accurate conversion parameters. We calibrate different sensor types with different gage lengths from 0.2m to 30m at our calibration facility. Key components are a motorized linear translation stage for applying controlled strain and a laser interferometer that is used as a reference measurement system. We can test different sensor types like ready to use strain transducers, strain sensor cables used for distributed sensing or even bare fiber sensors. Our results demonstrate that without calibration measurement errors of up to 20% can occur.