Abstract
In this Letter, an ultra-low noise level is achieved for a quasi-distributed acoustic sensing system. This system is based on a pulse compression technique and phase-noise compensation configuration. In this system, a prototype of a weak reflector array is designed and fabricated to have $\sim-40\,\,{\rm dB}$ reflectivity with a 20 m interval, and is used for improving the system’s signal-to-noise ratio. The two techniques reduce the noise level by 18 dB, among which 11.56 dB is obtained with the assistance of the phase-noise compensation configuration. In the experiment to simulate the scenario with a link loss of 20 km and 20 m array interval, the system noise level is demonstrated to be $-93.16\,\,{\rm dB}\,{\rm re}\,{\rm rad}/\surd {\rm Hz}$ at 500–2500 Hz, which equals a strain resolution of $92.84\,\,{\rm f}\varepsilon /\surd {\rm Hz}$ at 500–2500 Hz.
© 2019 Optical Society of America
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