对相位解调相位敏感光时域反射仪(φ-OTDR)系统中干涉衰落问题进行了研究。同一频率多次脉冲扫描显示出相似的衰落波形,而不同光频有不同的衰落波形。通过改进现有瑞利散射随机性和相干性物理模型,推出了瑞利散射系数是激光频率和有效折射率的函数,合理解释了上述实验现象。为了消除干涉衰落导致的系统误报问题,提出了一种基于多频率综合判决的方法,有效地区分并排除了误报,提高了整个φ-OTDR系统相位解调的准确性。 The problem of interference fading in the phase-demodulated phase-sensitive optical time domain reflectometer (φ-OTDR) system was studied. Multiple pulse scans at the same frequency show similar fading waveforms, but different fading frequencies have different fading waveforms. By improving the stochastic and coherent physical models of Rayleigh scattering, the Rayleigh scattering coefficient is derived as a function of the laser frequency and the effective refractive index, which explains the above experimental phenomena reasonably. In order to eliminate the system false alarm caused by interference fading, a method based on multi-frequency synthesis decision is proposed to effectively distinguish and eliminate false positives and improve the phase demodulation accuracy of φ-OTDR system.