利用相位调制器提升受激布里渊散射阈值，理论分析了相位调制器的调制深度及调制频率对受激布里渊散射阈值的影响。阈值提升量由调制深度确定，调制深度与半波电压有关。提出了外差法测量相位调制器的半波电压以便确定调制深度。实验测得相位调制器在调制频率50 MHz时的半波电压为3.7 V。实验研究了相位调制器调制频率为50 MHz，调制深度分别为1.435、2.631时的单模光纤受激布里渊散射阈值变化，其中调制深度为2.631时的受激布里渊散射阈值提高了6.7 dB，实验结果与理论计算值相符。在较小的驱动功率、较低的调制频率下获得了较高的受激布里渊散射阈值提升。

The phase modulator is used to increase the threshold of the stimulated Brillouin scattering. Effects of modulation depth and frequency on the threshold are analyzed. The increase of the threshold is determined by the modulation depth which is related to the half-wave voltage. A heterodyne method to measure the half-wave voltage of the phase modulator is proposed in order to determine the modulation depth. The results of the experiments demonstrate that the half-wave voltage is 3.7 V when modulation frequency is 50 MHz. The variation of the stimulated Brillouin scattering threshold are researched through experiments when the modulation frequency is 50 MHz and modulation depth is 1.435 and 2.631. Results show that the threshold increases 6.7 dB when modulation depth is 2.631, which matches the theoretic calculation. High threshold is obtained with low power and low modulation frequency.