Fast White Light Interferometry Demodulation Algorithm for Low-Finesse Fabry–Pérot Sensors

Over decades, the signal demodulation techniques of low-finesse Fabry-Pérot interferometer (FPI) sensors have been either slow with wide dynamic range and absolute measurement capability, or fast with narrow dynamic range and relative measurement capability. The tradeoff between the speed and the measurement capability has greatly limited the application of FPI-based sensors. In this letter, a novel high-speed white light interferometry (WLI) demodulation algorithm for low-finesse FPI has been developed. By realizing high-speed absolute demodulation utilizing full spectra, the new algorithm has the advantage of spectral drift immunity, high precision, and simultaneous ac and dc signal measurement capability, such as acoustic and temperature. A 70-kHz real-time WLI demodulation experiment was conducted in lab, in which the speed was limited only by the spectrometer hardware.