Design, Fabrication, Characterization, and Application of an Ultra-High Temperature 6H-SiC Sapphire Fiber Optic Vibration Sensor

Abstract

A 6H-SiC Sapphire fiber optic vibration sensor that can work at 1200 °C was designed, fabricated and tested in this paper. A sapphire fiber and a 6H-SiC vibration-sensitive element constituted the Fabry-Perot resonant cavity. The laser was input via the sapphire fiber, enabling the vibration signal to be converted to an optical signal through the Fabry-Perot cavity, and the vibration parameters were obtained by optical demodulation. The vibration-sensitive element consisted of a cantilever structure, whose structure parameters were determined by the combination of theoretical analysis and simulation. A nanosecond laser was employed to fabricate the 6H-SiC vibration-sensitive element to improve the processing efficiency and simplicity. The sensor was tested from room temperature to 1200 °C. The results showed that its frequency measurement sensitivity remains 0.9997 Hz/Hz from room temperature to 1200 °C, with the full-scale precision being 0.44% F.S. The sensor's output voltage is linearly correlated with the vibration acceleration from ambient temperature to 800 °C, making the acceleration measurement sensitivity 17.86 mV/g at 800 °C. The maximum frequency measurement error was 4.72 Hz when the sensor was at the field application of high temperature casting.

Keywords

• 6H-SiC
• ultra-high temperature
• sapphire fiber vibration sensor
• Fabry-Perot interferometer
• laser processing.