Quasi-distributed fiber-optic acoustic sensing system based on pulse compression technique and phase-noise compensation

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 ∼-40dB 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 -93.16dBrerad/√Hz at 500-2500 Hz, which equals a strain resolution of 92.84fε/√Hz at 500-2500 Hz.