为了提高激光测速系统的探测灵敏度，设计了马赫-曾德尔环形结构的平衡探测系统。基于光学多普勒效应，阐述了激光测速系统的工作原理，系统地阐述了平衡探测的实现方法，详细推导了平衡探测系统光电流的表达式，并分析得出其相对于相干探测的优势。利用光电流推导了平衡探测系统信噪比的表达式，并分析影响信噪比的主要因素。仿真实验结果表明：在相同输入光信号的条件下，无损耗分束镜的反射率在(0.2908,0.7092)区间内，或两个探测器的光电转换系数的比值在(0.4632，1)之间时平衡探测信噪比高于相干探测的信噪比。将平衡探测应用于多普勒测速，大大增强了测速系统的灵敏度。

The balanced detection system based on Mach-Zehnder type interferometer is applied to increase the detection sensitivity in laser Doppler velometer experimental system. Based on the Doppler effect, the principle of laser velometer system and the balanced detection realization method are described, the formula of light current is derived, and its advantages compared with the conventional coherent detection technique are analyzed. The formula of the signal-to-noise, which is derived by light current, is used to attain the influence factors. The simulation results demonstrate that when the reflection coefficient is set in (0.2908,0.7092) or the conversion coefficient ratio of two detectors is set in (0.4632,1), the dual balanced detection technique offers higher signal- to- noise ratio than the conventional detection technique. The sensitivity of the Doppler velometer system is strengthened with balanced detection technique.