Jiang Fei, Li Honglang, Zhang Zhenhai, Hu Zhewen, Hu Yanzhu, Zhang Yixin, Zhang Xuping
Opt Lett. 2019 Feb 15;44(4):911-914. doi: 10.1364/OL.44.000911.
Phase-sensitive optical time-domain reflectometry (ϕ-OTDR) based on coherent detection is one of the most widely used schemes to achieve fiber distributed acoustic sensing. In previous studies, a fairly high data acquisition speed is essential for the phase-measuring coherent ϕ-OTDR, thus leading to a severe computational burden. In this Letter, we first analyze the power spectrum of the beat signal and then propose the use of undersampling theory to reduce the need for high sampling frequency. Then we give the principle of selecting the matched sampling frequency and bandpass filter bandwidth so that the beat signal can be sampled without aliasing. The experimental results show that, when the central frequency of the beat signal is 200 MHz, its phase signal can be correctly demodulated even using a sampling rate as low as 71 MSa/s. This method can be extended to all existing coherent ϕ-OTDR systems with no or only a few modifications on them.
基于相干检测的相敏光时域反射仪（ϕ-OTDR）是实现光纤分布式声学传感应用最为广泛的方案之一。在以往的研究中，对于相位测量相干ϕ-OTDR而言，相当高的数据采集速度至关重要，从而导致了严重的计算负担。在本信函中，我们首先分析拍频信号的功率谱，然后提出利用欠采样理论来降低对高采样频率的需求。接着我们给出了选择匹配采样频率和带通滤波器带宽的原则，以便能够对拍频信号进行无混叠采样。实验结果表明，当拍频信号的中心频率为200 MHz时，即使使用低至71 MSa/s的采样率，其相位信号也能够被正确解调。该方法可以扩展到所有现有的相干ϕ-OTDR系统，只需对它们进行很少的修改或无需修改。
