Ultra-Stable Demodulation Based on Parameter- Optimized Frequency Estimation for Sapphire Fiber Microcavity High Temperature Sensing

Sapphire fiber microcavity (SFM) sensing, renowned for its robustness in harsh environments, has excellent potential for precision high-temperature thermometry. However, conventional demodulation techniques often suffer from large jumps and small step jumps under extreme thermal conditions. To address these challenges, this study introduces a novel demodulation algorithm based on parameter-optimized frequency estimation and phase compensation, enabling high-resolution temperature tracking from 25 °C to 1500 °C. Parameter-optimized frequency estimation is employed to eliminate large jumps, and phase compensation is employed to eliminate small step jumps. Experimental results verify that the proposed algorithm eliminates jump errors and reduces the number of data points by 32 times, respectively, which substantially enhances the stability of demodulation outcomes and decreases the demodulation time from 7.9 ms to 1.4 ms. Temperature sensitivity is 4.84 nm/°C at 1500 °C, and the mean resolution is 0.33 °C across the full temperature range, which places a solid base for accurate high-temperature measurement in practical environments.