提出一种基于时钟同源I/Q解调的相位敏感光时域反射系统解调方法.分析了调制信号与混频信号非同源不一致对解调结果的影响, 采用声光调制器调制信号、斩波信号与I/Q混频信号时钟同源的方法以消除残余频率的影响.实验采用双压电陶瓷作为扰动源, 通过I/Q解调实时获得后向瑞利散射光幅值和相位, 进而实现扰动的定位和还原.实验结果表明, 该系统能有效地探测到5 km和9 km处的正弦扰动, 定位信号信噪比分别达17.8 dB和16 dB, 相位解调结果准确还原正弦扰动, 与正弦曲线的拟合系数分别为0.994和0.991, 均方根误差分别为0.116和0.141.实验进一步验证了该方法能够测得不同扰动幅度下的相位正弦变化曲线, 并能准确得到不同扰动频率, 且扰动位置处相位变化幅度与扰动强度具有良好的线性关系, 线性拟合系数达0.992, 均方根误差为0.499, 均优于非同源解调结果.

A phase sensitive optical time domain reflection system demodulation method based on clock homologous I/Q demodulation is proposed. The influence of the non-homologous disagreement between the modulation signal and the mixing signal on the demodulation results is analyzed. The method using clock homologous modulation signal of the acoustic optical modulator, the chopper signal and the I/Q mixing signal is adopted to eliminate the influence of the residual frequency. Double piezoelectric ceramic is used as the disturbance source, and the amplitude and phase of the backward Rayleigh scattering light can be obtained in real time by I/Q demodulation, so as to achieve the location and reduction of the disturbance. The experimental results show that the system can detect the sinusoidal disturbances at 5 km and 9 km effectively, and the signal to noise ratio of the positioning signal is up to 17.8 dB and 16 dB, respectively. The phase demodulation results accurately restore the sinusoidal disturbance, and the fitting coefficients of the sinusoidal curves are 0.994 and 0.991 respectively, and the root mean square error is 0.116 and 0.141, respectively. Furthermore, the experiment verifies that the method can measure the phase sine curve under different disturbance amplitudes. The different disturbance frequencies can be obtained accurately, and the phase change amplitude at disturbance location has a good linear relationship with the disturbance intensity. The linear fitting coefficient is 0.992, and the root mean square error is 0.499, both are better than the non-homologous demodulation result.