Abstract
A single-shot distributed dynamic strain sensor is proposed with high spatial resolution and broad detection bandwidth. Linear frequency modulated pulse is employed as the probe pulse, which not only solves the trade-off between spatial resolution and sensing distance, but also avoids the time-consuming stepped frequency tuning process. The matrix of Rayleigh backscattering (RBS) at multiple frequencies over the fiber is obtained using the first probe pulse. The strain variation is retrieved from the corresponding frequency shift of the following probe pulses using RBS signature matching. In the demonstrational experiment, distributed vibration measurement with 0.9 m spatial resolution, 224 $p\varepsilon /\surd$ Hz strain resolution, 5 kHz response bandwidth and 25.7 dB signal-to-noise radio is realized over 10-km sensing fiber.
Highlights
Due to the unique advantages such as continuous sensing over long fiber, high sensitivity and robustness against harsh environment, distributed fiber-optic sensor based on Rayleigh backscattering (RBS) has been widely adopted in pipeline leakage detection, vertical seismic profiling, fence security [1]–[4], etc
When refractive index variation caused by external strain or temperature occurs at a certain position of the fiber under test (FUT), the profile pattern of RBS will change which can be compensated by the frequency shift of probe pulses
A single-shot continuous dynamic strain measurement with sub-meter spatial resolution based on RBS signature matching is demonstrated for the first time
Summary
Due to the unique advantages such as continuous sensing over long fiber, high sensitivity and robustness against harsh environment, distributed fiber-optic sensor based on Rayleigh backscattering (RBS) has been widely adopted in pipeline leakage detection, vertical seismic profiling, fence security [1]–[4], etc. The phase-demodulation method [6]– [8] calculates phase information of RBS by I/Q demodulation [9], heterodyne detection [10] or phase generated carrier scheme [11], and retrieves the strain or temperature information of the fiber. This method is promising for distributed acoustic sensing, because the small amount of computation is essential for the real-time processing of mass data. By replacing the step-by-step frequency sweeping with chirped probe pulses and matched filters, single-shot measurement is realized to obtain high response bandwidth, and the trade-off between spatial resolution and sensing distance is effectively mitigated simultaneously.
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