建立了Y分支光学调制器半波电压与工作波长和温度的数学模型，其半波电压随工作波长增加而增加、随温度增加而减小。设计实现了一种基于4阶波调制Sagnac干涉仪的半波电压自动测试系统，实现了半波电压的在线连续测量，相对测量精度达到8.5×10-6。用可调激光器光源，改变工作波长和环境温度，分别进行了1310 nm和1550 nm波段Y分支光学调制器半波电压的实际测量，通过实验测试确定了半波电压与波长和温度的相关性。结果表明，半波电压在这两个测试波段内与波长和温度均呈线性关系，波长相关系数为正，分别约为3.61×10-3 V/nm和9.54×10-3 V/nm；温度相关系数为负，分别约为-1.76×10-3 V/℃和-2.00×10-3 V/℃。实验结果验证了理论模型的正确性。

Models of the Y branch optical modulator′s half-wave voltage with wavelength and temperature are established. The half-wave voltage increases with wavelength increasing and temperature decreasing. A half-wave voltage automatic test system based on Sagnac interferometer modulated with four steps waveform is designed and it can measure half-wave voltage continuously on line. Relative measuring accuracy reaches 8.5×10-6. By changing working wavelength and temperature, the actual measurement of Y branch′s half-wave voltages in 1310 nm and 1550 nm band is realized by using a tunable laser as the light source. The results show that the half-wave voltage is linear with the temperature and the wavelength in the two test bands. The wavelength correlation coefficients are 3.61×10-3 V/nm and 9.54×10-3 V/nm, respectively, and the temperature correlation coefficients are -1.76×10-3 V/℃ and -2.00×10-3 V/℃, respectively. The experimental results verify the correctness of theoretical model.