Athermal fibre Bragg grating strain gauge with metal coating in measurement of thermal expansion coefficient

This study presents an athermal strain gauge based on fibre Bragg grating (FBG) in measuring thermal expansion coefficient of a low expansion nickel alloy block for demonstration. In order to design an athermal fibre Bragg grating strain gauge, the metal coating is electroless plated onto an optical fibre to function as a thermal compensator. Therefore, the Bragg wavelength will not shift with the ambient temperature change, and only shift regarding to the mechanical strain onto FBG. In measuring the thermal expansion coefficient of a low expansion nickel alloy block, data are in good agreement between the tests by using the athermal FBG and resistance strain gauge techniques. As a result, the athermal strain gauge based on FBG is demonstrated and feasible for the future applications.