High-speed, large dynamic range spectral domain interrogation of fiber-optic Fabry–Perot interferometric sensors

Abstract

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 ∼ 110 k H z 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.

Lithium Niobate Piezoelectric Actuator-Integrated Fiber Fabry-Pérot Tunable Filter with Ultrahigh Speed and Linearity

“…10,13 The mechanism of FPTF includes refractive index tuning, such as electro−optical 14 and liquid−crystal tuning, 15,16 as well as cavity-length tuning, such as mechanical, electrostatic, 17,18 and piezoelectric tuning. 19,20 Among these, electro−optic tunable filters 21−23 based on materials, such as lithium niobite (LiNbO 3 ), exhibit high-speed operation up to the gigahertz level. However, the relatively weak electro−optic coefficient and strong second-order Kerr effect of LiNbO 3 restrict the tuning range.…”

“…High-speed wavelength tuning is essential for optical fiber communication, , microwave photonics, − lasers, − spectroscopy, − sensors interrogation, and many other fields, where tunable filters are key elements. The Fabry-Pérot tunable filter (FPTF) is a versatile and reliable modulation approach with a high resolution and low optical insertion loss. , The mechanism of FPTF includes refractive index tuning, such as electro–optical and liquid–crystal tuning, , as well as cavity-length tuning, such as mechanical, electrostatic, , and piezoelectric tuning. , …”