Fabry–Perot interferometric humidity sensor based on PVA-GQDs composite film

To develop compact and sensitive humidity sensors for environmental monitoring and industrial applications, a fiber-optic Fabry–Perot interferometric humidity sensor based on PVA-GQDs composite film is proposed. The device consists of two polished fiber ceramic ferrules assembled in a ceramic split sleeve, with a humidity-sensitive PVA or PVA-GQDs coating on one ferrule end face. Experimental results show that the PVA-GQDs sensor achieves sensitivities of −1.1174 and −1.8188nm/%RH in the humidity ranges of 32%–50% RH and 50%–60% RH, respectively, which are higher than those of the pure PVA sensor. Moreover, it reduces temperature cross-sensitivity by 91.5% and exhibits a minimum standard error of 0.01655% RH. The proposed sensor provides a simple fabrication method, a compact structure, and a stable humidity response.