High-speed, large dynamic range spectraldomain interrogation of fiber-optic fabry perot interferometric sensors

We report high-speed, large dynamic range spectral domain interrogation of fiber-optic Fabry-Perot (FP) interferometric sensors. An optical interrogation system employing a piezoelectric FP tunable filter and an array of fiber-Bragg gratings for wavelength referencing is developed to acquire the reflection spectrum of FP sensors at a high interrogation speed with a wide wavelength range. A 98 nm wavelength interrogation range was obtained at the resonance frequency of similar to 110 kHz of the FP tunable filter. At this frequency, the resolution of the FP cavity length measurement was 1.8 nm. To examine the performance of the proposed high-speed spectral domain interrogation scheme, two diaphragm-based fiber-tip FP sensors (a pressure sensor and acoustic sensor) were interrogated. The pressure measurement results show that the high-speed spectral domain interrogation method has the advantages of being robust to light intensity fluctuations and having a much larger dynamic range compared with the conventional intensity-based interrogation method. Moreover, owing to its capability of measuring the absolute FP cavity length, the proposed interrogation system mitigates the sensitivity drift that intensity-based interrogation often suffers from. The acoustic measurement results demonstrate that the high-speed spectral domain interrogation method is capable of high-frequency acoustic measurements of up to 20 kHz. This work will benefit many applications that require high-speed interrogation of fiber-optic FP interferometric sensors. (C) 2022 Optica Publishing Group