激光多普勒测速系统的消偏振衰落技术研究

Technology of polarization induced fading elimination for laser Doppler velocimetry system

针对偏振衰落现象导致干涉信号丢失使激光多普勒测速系统可见度降低的问题,提出了一种消偏振衰落方案来保持系统检测信号的有效性。以激光多普勒测速系统的工作原理为基础,分析了偏振衰落产生的机理,建立了干涉信号可见度与偏振态的椭率角和方位角之间的数学模型,数值模拟研究了偏振衰落对系统可见度的影响。对基于三态偏振分集接收的消偏振衰落方案进行理论分析,搭建激光多普勒测速系统,并进行了实验验证。实验结果表明,系统可见度的最小值由接近0提高到0.32,验证了该方案的可行性和有效性。研究结果可为激光多普勒测速仪的工程性应用提供依据。

To solve the problem that the visibility of laser Doppler velocimetry（LDV）system is lower due to the interference signal loss caused by the polarization induced fading,a scheme of eliminating the polarization induced fading is proposed in this paper to keep the efficiency of the detection signals. The origin of polarization fading is analyzed Based on the working principle of LDV system. A mathematical model of interferential signal visibility and polarization states’ellipticity and azimuth angle is es-tablished. The influence of polarization induced fading on visibility of LDV system is analyzed with the way of numerical simula-tion. The theoretical analysis on the scheme of eliminating polarization induced fading is made on the basis of tri-state polariza-tion diversity. A new LDV system was established and demonstrated in experiment. The result shows that the minimum value of visibility can rise from nearly 0 to 0.32,which results in the feasibility and effectiveness of the scheme. It provided a basis for engineering application of LDV system.