A Temperature-independent Lateral Force Sensor using a Pair of FBGs

A novel arc-shaped FBG (fiber Bragg grating) lateral force sensor is developed with a pair of FBGs embedded symmetrically in an elastic bending beam. The FBG pair is produced with peak wavelength separation of about 0.4 nm. The FBG with shorter wavelength is located above the neutral layer and another with longer wavelength below the neutral layer. As a result, the two peak wavelengths of the FBG pair move apart with lateral force applied but move together in the same direction when surrounding temperature varies, both in a linear manner. A module with such structure has been studied both theoretically and experimentally, which proved that proper calibration makes such arc-shaped FBG sensor capable of simultaneous measurement of both temperature and lateral force. A very low temperature-dependency of only 0.04 pm/degC across the temperature range from 35degC to 82degC has been achieved, which makes it suitable for dynamic lateral force measurement even when the environmental temperature varies.