Highly sensitive balloon-like fiber interferometer based on GO nanomaterial coated for humidity measurement

Abstract

A highly sensitive balloon-like fiber interferometer based on Graphene Oxide (GO) nanomaterial coated for humidity measurement is proposed in this paper. The Mach-Zehnder interferometer (MZI) is formed by bending single-mode optical fiber. Then GO nanomaterials, which are sensitive to environmental humidity, are coated in the sensing region of the balloon-like fiber interferometer by physical deposition method. When ambient environmental relative humidity (RH) changes, GO nanomaterials will interact with water molecules, thus changing the refractive index (RI) around the sensing region of the balloon-like fiber interferometer, resulting in the shift of resonant wavelength. The measurement of different RH in the environment can be realized by evaluating the spectral drift. By comparing the RH sensitivity of the balloon-like fiber structure with different sensitive lengths, it can be found that the RH sensitivity of the balloon-like fiber structure is enhanced with the increase of the sensitive length. The experimental results of thickness optimization show that when the thickness of GO nanomaterial coating is about 250 nm, the sensitivity of 0.449 nm/%RH with a linearity of 0.992 can be achieved in the range of low humidity (less than 50 %RH). The response time and recovery time are about 4.8 s and 7.8 s. Moreover, the temperature sensitivity of the sensing structure with 250 nm GO nanomaterial is 0.102 nm/°C. Compared with the sensing structure without GO nanomaterial, the cross-influence of temperature can be effectively reduced by GO nanomaterial coating, so as to be better applied to humidity measurement. The balloon-like fiber sensors coated with GO nanomaterial possess good repeatability and stability, and offer broad application prospects for RH monitoring such as in the fields of biochemistry and medicine in the future.