相位敏感光时域反射系统相位模糊及解卷绕

对相位敏感光时域反射系统相位模糊问题和解卷绕进行了研究，推导了系统中扰动引入的相位变化的整个过程，分析了相位敏感光时域反射系统相位解调过程中产生相位模糊的原因。实验采用压电陶瓷作为扰动源，通过数字相干解调方法进行了相位解调。实验结果表明，相位模糊同时存在于每条相位解调曲线上和曲线之间，因此需要进行两次相位解卷绕消除相位模糊现象；同时，对实验中产生的相位错乱进行了分析，指出相位解卷绕阈值和扰动位置相位的剧烈变化导致了扰动位置相位解卷绕结果不准确，提出了采用相位差变化峰之后的临近位置处的相位变化来还原扰动。实验表明，这种方法能够正确还原扰动信号，能够对10 Hz~1.5 kHz范围内的扰动信号进行准确解调，可同时响应并解调光纤沿线多点扰动，且相位变化幅值与扰动强度具有良好的线性关系。

Phase ambiguity and unwrapping of phase-sensitive optical time-domain reflectometer

The phase ambiguity and unwrapping of phase-sensitive optical time domain reflectometer was investigated. The whole process of phase change introduced by the perturbation was deduced, and the reason for phase ambiguity in the phase demodulation was analyzed. The piezoelectric ceramic was used as the disturbance source, and phase demodulation was performed by digital coherent demodulation. The experimental results show that phase ambiguity exists on each phase demodulation curve and among these curves simultaneously. So it is necessary to perform two phases unwrapping to eliminate phase ambiguity. Meanwhile, the phase disorder in the experiment was analyzed. It was pointed out that the phase unwrapping threshold and the phase drastic change in the disturbance position caused the inaccurate phase unwrapping of the perturbation position. The phase change in the adjacent position following the phase difference peak was used to restore the perturbation. The experimental results show that this method can correctly restore the disturbance signal, can demodulate the disturbance signal in the range of 10 Hz-1.5 kHz accurately, can simultaneously demodulate and respond to multiple perturbations along the optical fiber and the phase change amplitude have a good linear relationship to the disturbances intensity.