Temperature sensitivity improvement in Bragg grating optical fiber coated by magnetron sputtering technique

In this work, our aim was to design and test a silver-coated fiber Bragg grating (FBG) sensor for temperature sensing applications. An FBG of 125 µm diameter was coated with silver by magnetron sputtering technique. Three coating thicknesses of 10, 20, and 30 nm were prepared and examined. Scanning electron microscopy (SEM) images confirmed the improvement in the roughness of fiber peel when the coating level is increased. The samples were analyzed at moderate ambient temperatures of 20, 60, and 100 °C to evaluate the temperature sensitivity in this range. The results indicated that the Bragg wavelength shift increased with silver coating thickness, and the highest sensitivity (Δ𝜆𝐵/𝑇) was 0.076 nm/°C for the 30 nm silver-coated fiber. Hence, the temperature sensitivity improves as the silver coating thickness increases.