Alekseev A E, Gorshkov B G, Potapov V T, Taranov M A, Simikin D E
Appl Opt. 2022 Jan 1;61(1):231-240. doi: 10.1364/AO.444494.
In the paper, we present a qualitative analysis of the dual-pulse phase optical time domain reflectometry (phase-OTDR) response to uniform and nonuniform propagating fiber strain. It is found that on average over all realizations of scattering centers the response of the dual-pulse phase-OTDR is linear with respect to an external perturbation. Meanwhile, individual responses contain random phase jumps, which are an intrinsic property of phase-OTDR. These jumps are the result of nonlinear responses of the scattering fiber segments and arise due to interference of random backscattered fields varying in time. Two types of phase jumps are considered: jumps and 2 jumps; the first type is caused by the fading in phase-OTDR spatial channel, while the second type occurs when a nonuniform perturbation propagates along the fiber. The origin of the phase jumps is explained by considering the simulated response on the complex plane. It is shown that the distribution of 2 jumps can be well described by the Gaussian probability mass function (PMF), provided the number of 2 jumps is large. The conducted experiments on the registration of uniform and nonuniform fiber strain confirm the presence of the jumps in the phase-OTDR response.
在本文中，我们对双脉冲相位光时域反射仪（相位OTDR）对均匀和非均匀传播光纤应变的响应进行了定性分析。结果发现，在散射中心的所有实现情况下，双脉冲相位OTDR的响应相对于外部扰动平均而言是线性的。同时，各个响应包含随机相位跳变，这是相位OTDR的固有特性。这些跳变是散射光纤段非线性响应的结果，并且是由于随时间变化的随机后向散射场的干涉而产生的。考虑了两种类型的相位跳变：1跳变和2跳变；第一种类型是由相位OTDR空间通道中的衰落引起的，而第二种类型发生在非均匀扰动沿光纤传播时。通过考虑复平面上的模拟响应来解释相位跳变的起源。结果表明，如果2跳变的数量很大，则2跳变的分布可以用高斯概率质量函数（PMF）很好地描述。对均匀和非均匀光纤应变的记录进行的实验证实了相位OTDR响应中存在跳变。
