Abstract
In the fiber sensing research area, a pair of sharp contradictions is highlighted: high sensitivity and large dynamic range. In addition, the question of how to enable user-editable features for fiber optic sensors is gaining more and more attention. This letter presents a fiber acoustic sensor with real-time controllable sensitivity based on the optical vernier effect, which is possibly a solution to such a problem. The optical vernier structure with amplified and real-time tunable detection sensitivity is formed by cascading a Sagnac interferometer and a laboratory-made tunable Fabry–Perot interferometer (FPI). Sound pressure and frequency of the acoustic signal can be all-optically demodulated simultaneously by spectral reading and spectral scanning method, respectively. Experimental results show a real-time controllable acoustic sensitivity (1×, 5×, and 10× are demonstrated) and a maximum sensitivity is as high as 37.1 nm/Pa (10× of single FPI) within relatively large sound pressure range of 62.2–92.4 dB. By adjusting the FPI cavity length in real time, sensitivity can be controlled to meet the needs of different users or occasions. The proposed sensor has merits of controllable sensitivity in real time, high sensitivity, and large dynamic range, enabling the applications related but not limited to acoustic sensing.
Highlights
Optical fiber acoustic sensors (OFAS) have attracted considerable attention in many fields, such as structural health detection [1], seismic observation [2], leakage detection [3], and underwater positioning [4], etc
This paper presents an optical fiber acoustic sensor with real-time controllable sensitivity based on optical vernier effect
We demonstrated an OFAS that combines the merits of high sensitivity and large dynamic range simultaneously
Summary
Optical fiber acoustic sensors (OFAS) have attracted considerable attention in many fields, such as structural health detection [1], seismic observation [2], leakage detection [3], and underwater positioning [4], etc. The edge filtering method needs complicated Q-point tracking and stabilization techniques [22], [26]; the PGC method requires precise control on the external modulation signal; And strict wavelength control is necessary for the dual-wavelength orthogonal method; In contrast, the spectrum interrogation method, which demodulates the dynamic signal by extracting the ripple spectrum from the disturbed spectrum, avoids the shortcomings of the above methods, and greatly eliminates environmental disturbances such as temperature and refractive index This method has good application prospect in the research of OFAS. The proposed sensor offers several advantages such as controllable sensitivity in real time, high sensitivity and large dynamic range, which further benefits its practical sensing application
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