We propose and experimentally demonstrate a novel interference fading suppression method for phase-sensitive optical time domain reflectometry (φ-OTDR) using space-division multiplexed (SDM) pulse probes in a few-mode fiber. The SDM probes consist of multiple different modes, and three spatial modes (LP01, LP11a, and LP11b) are used in this work for the proof of concept. Firstly, the Rayleigh backscattering light of different modes is experimentally characterized, and it turns out that the waveforms of the φ-OTDR traces for distinct modes are all different and independent. Thanks to the spatial difference of the fading positions for distinct modes, multiple probes from spatially multiplexed modes can be used to suppress the interference fading in φ-OTDR. Then, the performances of the φ-OTDR systems using a single probe and multiple probes are evaluated and compared. Specifically, the statistical analysis shows that the fading probabilities over both the fiber length and the time scale are reduced significantly by using multiple SDM probes, which verifies the significant performance improvement on fading suppression. By introducing the concept of SDM to φ-OTDR, the proposed novel interference fading suppression method avoids the complicated frequency or phase modulation, which has the advantages of simplicity, good effectiveness and high reliability.

中文翻译：

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使用空分复用探头的φ-OTDR中的干扰衰落抑制

我们提出并实验证明了一种新颖的干涉衰落抑制方法，用于在几模光纤中使用空分复用（SDM）脉冲探头的相敏光时域反射仪（φ-OTDR）。SDM探针由多种不同的模式组成，并且在这项工作中使用了三种空间模式（LP01，LP11a和LP11b）来进行概念验证。首先，对不同模式的瑞利背散射光进行了实验表征，结果表明，不同模式的φ-OTDR迹线的波形都是不同且独立的。由于不同模式的衰落位置存在空间差异，因此可以使用来自空间复用模式的多个探头来抑制φ-OTDR中的干扰衰落。然后，评估并比较了使用单个探针和多个探针的φ-OTDR系统的性能。具体而言，统计分析表明，通过使用多个SDM探针，可以显着降低光纤长度和时间尺度上的衰落概率，这证明了在抑制衰落方面的显着性能提升。通过将SDM的概念引入到φ-OTDR中，该新颖的干扰衰落抑制方法避免了复杂的频率或相位调制，具有简单，有效，可靠性高的优点。验证了在抑制衰落方面的显着性能提升。通过将SDM的概念引入到φ-OTDR中，该新颖的干扰衰落抑制方法避免了复杂的频率或相位调制，具有简单，有效，可靠性高的优点。验证了在抑制衰落方面的显着性能提升。通过将SDM的概念引入到φ-OTDR中，该新颖的干扰衰落抑制方法避免了复杂的频率或相位调制，具有简单，有效，可靠性高的优点。