Wide measurement-range fiber-optic temperature sensor based on ZnO thin film

• A fiber temperature sensor with a wide measurement range 373–873 K and a resolution of ~1 °C is proposed.
• The effect of the incident light bandwidth on the absorption edge is studied for the first time.
• The theoretical measurement range can extend from 10 K to 1800 K.

Based on the spectral absorption effect of ZnO thin film, a wide measurement-range fiber optical temperature sensor with a sensitivity of 0.06 m/°C is proposed. By optimally designing the sensing head structure and using the light sources with different bandwidths (8 nm, 30 nm and 47 nm), the temperature-dependent transmission spectra from the sensor are measured and investigated experimentally. The results show that the spectral transmittance curves become smoother with the increased bandwidth of the incident light, and the red shift of the absorption edge is almost the same when the temperature is increased by 50 K. Using the annealed ZnO thin film and the optimized light source (47 nm), the temperature resolution of the designed sensor reaches approximately 1 °C in a wide temperature range 373–873 K. Besides a wide measurement range, the temperature sensor has some other advantages such as a simple optical structure, a low cost and a good stability.