结合偏振干涉法，详细分析了相位－偏振调制器的输入电压与其延迟相位的关系，并导出了相位-偏振调制器的输出光强与其延迟相位的数学表达式。研究结果表明，采用偏振干涉法可以使相位－偏振调制器获得稳定的干涉光强，从而可以精确地测量出相位－偏振调制器的伏－相特征曲线。测量结果表明，相位－偏振调制器的伏－相特征曲线具有良好的线性特性。

By using interference method of polarization,the relation of input voltage and phase delay of phase-polarization modulator is discussed in detail,and the expression of the intensity of output interference light and phase delay of phase modulator is deduced. The result shows that the phase-polarization modulator can obtain steady interference light by using interference method of polarization,so the voltage-phase characteristic curve of phase-polarization modulator can be measured accurately. The result of the measurement shows that voltage-phase characteristic curve of phase-polarization modulator has good linearity.