Dataset 1 Single-mode sapphire fiber temperature sensor

Sapphire fiber can withstand temperatures of around 2000°C, but it is multimoded, giving poor precision sensors. We have demonstrated a single-mode sapphire fiber Bragg grating temperature sensor operating up to 1200°C. A single-mode sapphire fiber was formed by writing a depressed cladding waveguide along the length of a 100-µm diameter sapphire fiber using a femtosecond laser. A second-order Bragg grating sensor was inscribed within the waveguide, achieving a reflectivity of >90% and a narrow bandwidth of <0.5 nm. The single-mode sapphire fiber was fusion spliced to standard silica single-mode fiber. The sensor was vibration-tested over a 10 Hz to 30 kHz range with 30 µm displacement, resulting in minimal Bragg wavelength variation of <30 pm standard deviation. The sensor was furnace-tested to 1200°C, showing ±0.08% repeatability above 1000°C. This demonstrates the high precision sensing capability of single-mode sapphire fiber Bragg grating sensors with end-to-end single mode interrogation.