Spectrum ameliorative optical fiber temperature sensor based on hollow-core fiber and inner zinc oxide film

•This paper proposes an effective method of improving output spectrum of HCF-based sensors by coating ZnO film on inwall.•The thin ZnO film can increase the extinction ratio and reduce the transmission loss of this sensor distinctly.•The length of sensing area is only 6 mm.•The proposed sensor can realize high temperature measurement up to 460 °C.

The conventional optical fiber sensors based on hollow-core fiber (HCF) are suitable for high-temperature measurement. However, the limit effect of HCF's air core on transmission light is weak and thus result in a large transmission loss. Therefore, this paper proposed and demonstrated a spectrum ameliorative optical fiber temperature sensor based on HCF and inner zinc oxide (ZnO) film. The HCF's inwall is coated with a layer of thin ZnO film to enhance the limitation on the transmission light and improve the output spectrum. Experimental results show that the extinction ratio of transmission spectrum increase about 5 dB and the spectral pattern is more smooth and uniform. This method of coating film on the HCF's inwall to improve output spectrum is effective. The proposed sensor can realize high temperature measurement up to 460 °C.