Self-Filtering High-Resolution Dual-Sapphire-Fiber-Based High-Temperature Sensor

We present a self-filtering and high-resolution sapphire fiber sensor based on an extrinsic Fabry-Pérot interferometer for high-temperature sensing. The sensor has a high fringe visibility and signal-to-noise ratio. Two well-polished sapphire fibers are aligned side by side to realize shunting transmission between the background light and the interference signal. Heterogeneous fiber splicing between the sapphire fiber and the multimode silica fiber is realized for long-distance transmission of signals. A C-plane double-sided polished sapphire wafer is mounted perpendicularly to the tip of sapphire fibers as the Fabry-Pérot cavity. The crosstalk noise from input light caused by heterogeneous fiber splicing and fiber tip reflection is filtered out to reach a higher signal quality. A series of comparison experiments from 100 to 1080 °C were carried out for the difference in characteristics between self-filtering sensors and traditional sapphire fiber Fabry-Pérot sensors. The self-filtering sensor's fringe visibility was above 43.96%, and its signal-to-noise ratio was above 20.14 dB. The temperature resolution of the self-filtering sensor was better than 0.25 °C.