High-performance humidity sensor based on a micro-nano fiber Bragg grating coated with graphene oxide

A high-performance relative humidity (RH) sensor based on a micro-nano fiber Bragg grating (MFBG) coated with a graphene oxide (GO) film is fabricated with a chemical corrosion technique and optically driven deposition method. The diameter of MFBG is corroded to about 12 µm. GO film with the thickness of about 2.5 µm is uniformly coated on the MFBG surface. The change of RH results in the change of refractive index (RI) of GO film, that is, the change of effective RI of MFBG, which will at last result in the shift of reflected wavelength. The experimental results show that there is a good linear relationship between the wavelength shift of MFBG and RH changes in the RH range of 20% to 80% at constant temperature. The sensitivity is 17.361 pm/RH% and the linear correlation coefficient is 99.89%. In order to eliminate the impact of temperature cross sensitivity, the relative measurement is adopted and similar results are obtained. The average response and recovery times are measured to be about 3.2 s and 8.3 s, respectively. The sensor has the advantages of long stability, reversibility, quick response and simple structure. With such high performance, it can be used in widespread potential fields, such as biology, chemical processing and food processing.