Mach-Zehnder干涉仪条纹成像多普勒激光雷达风速反演及视场展宽技术

Wind velocity retrieval and field widening techniques of fringe-imaging Mach-Zehnder interferometer for Doppler lidar

相对于传统多普勒鉴频器Fabry-Perot干涉仪,Mach-Zehnder干涉仪(MZI)具有透过率高、直线条纹易于探测、可进行视场展宽等优点.本文设计了基于条纹成像MZI的非相干多普勒测风激光雷达系统,构建了风速反演的数学模型,利用MZI视场展宽技术优化了激光雷达系统的性能.数值仿真实现了MZI鉴频系统干涉条纹图样的理想输出,采用Sine Sqr函数拟合法获取了高精度的多普勒频移前后干涉条纹的移动距离,并通过视场补偿减小了入射角对MZI光程差的影响,从而实现视场展宽.结果表明:采用Sine Sqr函数拟合法可获得在±100 m·s-1的径向风速范围内<0.45 m·s-1的风速误差,克服了条纹重心法反演风速不稳定性的缺点;视场展宽技术在不降低鉴频性能的情况下,能最大补偿1°的视场角.MZI条纹成像多普勒激光雷达应用技术的探讨将为中高层大气风速激光雷达测量系统的实际开发奠定良好的基础.

Compared with the traditional Doppler frequency discriminator Fabry-Perot interferometer, Mach-Zehnder inter-ferometer （MZI） has the advantages in high transmittance, linear parallel fringes instead of circular rings and wide field of view. An incoherent Doppler wind lidar system is demonstrated based on a fringe-imaging MZI. The mathematical model of wind velocity retrieval is derived, and the field widening of MZI is also used to optimize the performance of lidar system. The ideal fringe pattern outputs are obtained by numerical simulation, and the SineSqr function fitting method is proposed to determine the high-precision displacement of fringes after a Doppler shift. Furthermore, the field widening of MZI can be realized by field compensation which reduces the effect of the incidence angle on optical path difference. The results show that the wind velocity error obtained by SineSqr function fitting method is less than 0.45 m·s^-11 at the line-of-sight wind velocity in a range from -100 m·s^-1 to 100 m·s^-1, which overcomes the instability of wind velocity retrieval by the gravity method. A full-angle field of view of 1° for MZI frequency discriminator without significant performance reduction is also achieved. These supplied discussion of the application techniques for Doppler lidar based on MZI fringe technique would promote the practical development of Doppler lidar for wind velocity measurement of the middle and upper atmosphere.