Redding Brandon, Murray Matthew J, Donko Andrei, Beresna Martynas, Masoudi Ali, Brambilla Gilberto
Opt Express. 2020 May 11;28(10):14638-14647. doi: 10.1364/OE.389212.
We present a low-noise distributed acoustic sensor using enhanced backscattering fiber with a series of localized reflectors. The point reflectors were inscribed in a standard telecom fiber in a fully automated system by focusing an ultra-fast laser through the fiber cladding. The inscribed reflectors provided a reflectance of -53 dB, significantly higher than the Rayleigh backscattering level of -70 dB/m, despite adding only 0.01 dB of loss per 100 reflection points. We constructed a coherent φ-OTDR system using a double-pulse architecture to probe the enhanced backscattering fiber. Using this system, we found that the point reflectors enabled an average phase noise of -91 dB (re rad/Hz), 20 dB lower than sensors formed using Rayleigh backscattering in the same fiber. The sensors are immune to interference fading, exhibit a high degree of linearity, and demonstrate excellent non-local signal suppression (>50 dB). This work illustrates the potential for low-cost enhanced backscattering fiber to enable low-noise, long-range distributed acoustic sensing.
我们展示了一种使用带有一系列局部反射器的增强型背向散射光纤的低噪声分布式声学传感器。通过在全自动系统中，将超快激光聚焦穿过光纤包层，在标准电信光纤中写入点状反射器。尽管每100个反射点仅增加0.01 dB的损耗，但所写入的反射器提供了-53 dB的反射率，显著高于-70 dB/m的瑞利背向散射水平。我们构建了一个使用双脉冲架构的相干φ-OTDR系统来探测增强型背向散射光纤。使用该系统，我们发现点状反射器能够实现-91 dB（相对于rad/Hz）的平均相位噪声，比在同一光纤中使用瑞利背向散射形成的传感器低20 dB。这些传感器不受干扰衰落影响，具有高度线性，并且展现出出色的非局部信号抑制（>50 dB）。这项工作说明了低成本增强型背向散射光纤实现低噪声、远程分布式声学传感的潜力。
