Multilayer metal-coated fiber Bragg grating for high-temperature sensing

In this study, a copper coating was deposited on the surface of a fiber Bragg grating (FBG) via electroplating. We compared the temperature responses of the uncoated and copper -coated FBGs from 20 degrees C to 1000 degrees C. Under high -temperature conditions, copper diffused into the FBG to form copper crystals, and the copper coating gradually underwent high -temperature oxidation. This reduced the sensitivity and spectral consistency of the copper -coated FBG. A multilayer metal -coated FBG was prepared with an inner layer of nickel, outer layer of gold, and copper layer in the middle. The multilayer FBG exhibited a temperature sensitivity of 23.1-23.53 pm/ degrees C. Furthermore, it showed the coating -enhancement effect and good linearity after multiple thermal cycles. The multilayer metal -coated FBG not only shows high -temperature sensitization but also solves the problem of bare FBGs being extremely fragile after experiencing high temperatures. This study provides a feasible solution for the application of FBGs in extremely high -temperature environments.