A study of the temperature sensitivity of fiber Bragg gratings after metallization

Abstract

In order to embed fiber sensors into metal material, the fiber sensors must be protected.Experiments using electroless plating of a nickel-clad fiber Bragg grating (FBG) have beencarried out four times in order to learn its temperature sensitivity and the relationshipbetween temperature sensitivity and plating thickness. In each experiment, the platingthickness and the corresponding temperature sensitivity were measured, thus achieving thetemperature sensitivities of nickel-clad FBG with different plating thickness. A techniquefor FBG surface electroless plating is proposed. The strains and stresses on thenickel-clad FBG under varied temperature are analysed. The theoretical model of thetemperature sensitivity of nickel-clad FBG is deduced. The relationship betweentemperature sensitivity and plating thickness of nickel-clad FBG is analysed in theoryand verified by experiment. When plating thicknesses are 1.42, 4.26, 15.625 and38.35 µm,the temperature sensitivities of FBG, with a wavelength of 1544.06 nm, are 12.1354, 14.3092, 17.9334and 19.6499 pm °C−1 in theory and the experimental results are 12.09, 13.83, 17.48 and19.605 pm °C−1. The results of theoretical analysis match those from experiments. The hysteresis ofthe wave-shift is discussed with hysteresis disappearing after heat treatment.