Temperature Compensated FBG Displacement Sensor for Long-Range Applications

This letter presents an improved fiber Bragg grating (FBG) displacement sensor for long-range measurements. A mechanical transfer structure is designed and developed, which converts the displacement of a measurement wire to the elastic deflection of a sensing arm. The wavelength shift difference between two FBGs symmetrically pasted on the sensing arm is found to be proportional to the displacement. The experimental results show that this design has a displacement sensitivity of 23.80 pm/mm within a measurement range of 0-150 mm. This improved displacement sensor shows good temperature compensation with the very low temperature sensitivity of 0.076 pm/°C for a temperature range of -40-120 °C. This sensor can be utilized for long-range and high endurance displacement measurement applications in harsh industrial environment.