A High-Performance DAS System Using Point-Backscattering-Enhanced Fiber and Study of Its Noise Characteristics

Distributed acoustic sensing (DAS) system with point-backscattering-enhanced fiber (PBSEF) has the capability of breaking the signal-to-noise ratio limit of traditional DAS; therefore, it would become one of the most powerful DAS technologies and expand the applications of DAS systems. To optimize the performance when designing DAS system with PBSEF, it is crucial to understand the relationship between the system noise and the reflectance enhancement, which is yet to be systematically studied. In this article, both experimental investigation and theoretical analysis of a typical $3\times3$ heterodyne DAS system with PBSEF were carried out. The relationship between system noise level and the reflectance enhancement was studied by both experiments and simulations, and the results, with good agreements between each other, show that the system noise level drops exponentially as the reflectance increases. With 29.7-dB reflectance enhancement, the system noise level decreased from 9.5 to 0.44 $\text{p}\varepsilon /\surd $ Hz. The influences of intensity noise and phase noise were also analyzed based on the theoretical model. The findings of the quantitative relationship and the noise influence can be used as a universal guidance for the design of PBSEF-based high performance DAS systems.