Abstract

Distributed acoustic sensing is a recently developed technique that has demonstrated its utility in vibration and strain detection. However, for conventional demodulating algorithm, the dynamic range of vibration sensing is limited by the defect of the unwrapping algorithm and low-frequency deviation noise. We proposed and experimentally demonstrated a demodulating scheme of enlarging the dynamic range of vibration sensing. The proposed time differential method can demodulate the large vibration signal undistortedly, and weighted-gauge approach can efficiently suppress the low-frequency deviation noise. Large vibration sensing has been performed on a 10 km fiber, successfully measured 2.367 με with 200 Hz vibration. The maximum measurable result of the temporal differential (TD) method is 100.1 times larger than the conventional method. Moreover, small and low-frequency vibration sensing has been conducted. Weighted-gauge approach effectively increases the SNR over 20 dB for the vibration signal with frequency under 100 Hz. The proposed scheme enables flexible access on the traditional Φ-OTDR system without extra hardware complexity.

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