Broadband high-sensitivity acoustic sensing based on Brillouin random fiber laser

Abstract

In this study, a broadband high-sensitivity fiber-optic acoustic sensor with simple structure and low cost based on Brillouin random fiber laser (BRFL) is proposed and demonstrated theoretically and experimentally. A double coupler fiber ring resonator (DCFRR) in the BRFL, which filters out redundant random modes and ensures high-quality lasing output, is utilized as the sensing element for acoustic sensing thanks to the high sensitivity of the transmission spectrum of the DCFRR to its cavity length variations induced by acoustic perturbations. The resultant shift in the transmission spectrum of the DCFRR by the external acoustic vibrations modulates the gain available inside the BRFL cavity and transfers the resonant random mode, leading to directly modulated lasing intensity output from the BRFL and thus the feasibility for acoustic signal recovery. The experimental results demonstrate the broadband frequency response and high sensitivity feature of the proposed BRFL-based acoustic sensor, which is able to detect acoustic signals in both low-frequency (2 Hz ∼ 500 Hz) and high-frequency (0.5 kHz ∼ 200 kHz) regions with high signal-to-noise ratio beyond 10 dB. In addition, the structural flexibility of the proposed sensor enables remote acoustic sensing, making it an ideal candidate for acoustic applications in harsh environments.