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基于外差检测与前向拉曼放大相结合的思路,提出了一种能实现长距离传感并同时具备高空间分辨率和高信噪比(SNR)的新型相位敏感光时域反射仪(Φ-OTDR)。讨论了如何优化入纤脉冲光和拉曼泵浦光功率,尽可能降低非线性效应对系统的不良影响,并在此基础上讨论了外差检测相比直接检测对系统性能的改善。实验证明,本文提出的Φ-OTDR传感距离可达到103km,为迄今报道的最长距离,空间分辨率为15.7m,SNR为7.89dB,其应用在管道防开挖现场试验中得到较好的验证。
Based on the idea of heterodyne detection and forward Raman amplification, a novel phase-sensitive optical time-domain reflectometer with long-range sensing and high spatial resolution and high signal-to-noise ratio (SNR) Φ-OTDR). This paper discusses how to optimize the power of fiber-pulsed and Raman pump light and minimize the adverse effects of nonlinear effects on the system. Based on this, the improvement of system performance compared with direct detection is discussed. Experiments show that the proposed Φ-OTDR sensing distance can reach 103km, which is the longest reported distance so far. The spatial resolution is 15.7m and the SNR is 7.89dB. The application of this method in field tests of pipeline excavation is better verification.