A small displacement sensor with simple beam based on fiber bragg grating

A small fiber Bragg grating (FBG) displacement sensor with sizes of 30mm x 4mm x 3mm is presented to measure displacements in narrow spaces. Its design is based on the linear relationship between the strain and deflection of the sensing element which converts displacement signals into strain signals of FBG by using a simply supported beam, so the measured strain of the sensing element by FBG can be used to express the displacement of the detected object surface. The temperature disturbance of FBG is solved by the means of differential strain of two FBGs which are stuck on the upper and bottom sui-faces of the sensing element, respectively. The calibration results showed that the displacement sensitivity is 4.73nm/mm in a full 1mm range, the linearity of the sensor is less than 1%, and the temperature stability is less than 1% in a range from 20 degrees C to 60 degrees C.