Abstract
We have proposed and demonstrated a double-cladding fiber (DCF) with cladding-mode resonance property for broadband acoustic vibration sensing. Since the fundamental mode in the core waveguide is able to be coupled to LP05 mode in the tube waveguide once the phase-matching condition is fulfilled, the transmission spectrum can exhibit a dip with a large extinction ratio. An acoustic vibration could induce the wavelength shift of such transmission spectrum, so that the intensity variation at a wavelength near the dip is coded with the information of the acoustic vibration signal. By demodulating the response of intensity variation, the frequency of the applied acoustic vibration signal can be recovered. Such a DCF-based sensor with an intensity modulation could measure the acoustic vibration with a broadband frequency range from 1 Hz to 400 kHz and exhibits the maximum signal-to-noise ratio (SNR) of ~80.79 dB when the vibration frequency is 20 kHz. The obtained results show that the proposed DCF-based acoustic vibration sensor has a potential application in environmental assessment, structural damage detection, and health monitoring.
Highlights
Acoustic vibration detection has been widely applied in many fields such as environmental assessment [1], structural damage detection [2], and health monitoring [3]
A broadband acoustic vibration sensor with the single mode fiber (SMF)-double-cladding fiber (DCF)-SMF scheme has been proposed for the first time
Such scheme presents a band-reject filter spectrum due to the cladding-mode resonance of DCF, which is sensitive to the acoustic vibration induced structure change
Summary
Guanghui SUI et al.: Broadband Acoustic Vibration Sensor Based on Cladding-Mode Resonance of Double-Cladding Fiber and even a very little phase change caused by the acoustic signal can be discovered, which makes them show an ultrahigh sensitivity. In the above sensors, their middle structures are usually very fragile so they often require special drawing craft and packaging technique Some of these structures need extra fabrication such as tapering, etching, and grating to help excite the higher-order modes, which degrades the robustness of fiber sensors. By demodulating the intensity variation, the applied acoustic vibration signal can be detected Such DCF-based sensor with an intensity modulation could measure the acoustic vibration with a broadband frequency range. Compared with the aforementioned fiber-based acoustic vibration sensor, the proposed DCF sensor has advantages including simple structure, elimination of post fabrication and complicated algorithms of demodulation, broadband, low cost, and compatibility to the commercial SMF. The obtained results show that the proposed DCF-based acoustic vibration sensor has a potential application in environmental assessment, structural damage detection, health monitoring, etc
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