Study of temperature sensing performance of bimetallic layer MFBG

Abstract

To improve the strength and performance of FBG (fiber Bragg grating), they are often encapsulated and protected or surface metallized. In this paper, based on the thermoelastic theory of J.M.C. Duhamel and F.E. Neumann, a thermal sensitivity model for bimetallic layer MFBG (metalized FBG) is established, and the thermal sensitivity performance parameters are analyzed for MFBG with single metal layers and those with Ni and Ti bimetallic layers deposited on the surface. The thermal sensitivity coefficient of the MFBG gradually stabilizes as the thickness of the metal coating increases. To verify the rationality of the theoretical model, Ni-Ti MFBG (double-layer MFBG with Ni as the outer metal and Ti as the inner metal) were prepared by magnetron sputtering with electroplating for thickening, and the plating process and formulation were optimized. The thermal sensing performance experiments of Ni-Ti MFBG and ordinary bare FBG were conducted together. The metallization of FBG can improve the temperature sensitivity of FBG, and the relative error between the experimental data and the theoretical value is less than 5 %. When h1 (the thickness of the inner metal layer) = 1 µm, h2 (the thickness of the outer metal layer) keeps increasing, the change trend of the temperature sensitivity of Ni-Ti-MFBG is consistent with the conclusion reached in the theory, which strongly proves the validity and reasonableness of the established bimetallic layer MFBG thermal sensing model, and the results of this paper have good theoretical guidance significance for the research on the connection between FBG and electromechanical components.