Temperature insensitive fiber optical displacement sensors based on double fiber Bragg gratings

A temperature insensitive fiber optical displacement sensor based on double Bragg gratings is presented and experimentally demonstrated. The sensor is constructed by a trapezoid slid block and two isosceles cantilevered beams, and two fiber Bragg gratings (FBG) that are glued on the two beams. The displacement can be measured by interrogating the wavelength difference of the two FBGs, and the temperature dependence is greatly reduced. Experimental results show that a displacement sensitivity of 120 pm/mm and a temperature dependence of 2.1 pm/°C are achieved.