Hollow Microsphere Fabry–Perot Cavity for Sensing Applications

Two different sensing structures based on a hollow microsphere Fabry-Perot cavity are proposed. The hollow spheroidal cavities are fabricated resorting only to fusion splicing. The first structure is based on a hollow microsphere located at the fiber end and works as a probe sensor. The structure was subjected to lateral load pressure and presents a sensitivity of 1.56 ± 0.01 nm/N. The second proposed sensor relies on an in-line hollow microsphere. The sensing structure allows the detection of lateral loading, with a sensitivity of 2.62 ± 0.02 nm/N, as well as strain detection, with a sensitivity of 4.66 ± 0.03 pm/με. The two proposed sensors present similar response when subjected to temperature and have low thermal sensitivity.