Metal coating of fiber Bragg grating and the temperature sensing character after metallization

In this study, the fiber Bragg grating (FBG) was metallized with a nickel coat using an electroless-electro plating method. Under the optimum conditions, the surface of chemical plating and electroplating coat are smooth and compact, there is not any visible defect in the cross-section. The effects of the nickel coat on the properties of the fiber sensor were studied. With this plating method, the FBG can be well protected and its sensing properties can be changed. When the temperature is changed, a thermal stress between the metal coat and the fiber will be induced because of the thermal expansion coefficients difference. The thermal stress influence on the temperature sensing properties of the metalized FBG was analyzed, and a physical-mathematical model for FBG temperature sensing was presented. Experimental results show the mathematical model is feasible to explain the mechanism of temperature sensitivity enhancement for metalized FBG.