【作者】 王建银；

【导师】 陈建国；

【作者基本信息】 四川大学 ， 光学， 2007， 硕士

【摘要】 激光多普勒测风雷达是利用激光多普勒效应测量大气风场速度的一种技术。与传统测风工具和方法相比，激光多普勒测风雷达具有不影响目标运动、信号稳定、精度高、非接触等优点，被广泛地应用于气象领域、军事领域、航天领域、科学领域等。由于其良好的发展前景，近年来，国内外在这方面发展都较迅速，美、英、俄、法等国已有相关产品报导。激光测风雷达通常由激光器、入射光学单元、接受或者收集光学单元、多普勒信号处理器（探测器）、数据处理系统等组成。由于气溶胶在大气中的良好跟随性，所以对于风速的测量，实际上是对大气中气溶胶运动速度的测量。通过探测大气中气溶胶对激光的散射来获得多普勒频移，从而算出相应的风速值。在本文中，分别介绍了基于CO₂激光器的相干测速和基于1.55μm光纤激光器的全光纤相干测风两种实验系统。测速系统是利用一片薄膜偏振片（TFP）将CO₂激光器发射的激光分为主振和本振两束光，其中主振光通过收／发合一的天线平行发射到空中，照射在运动目标上，散射光再通过天线回到系统后与本振光发生相干混频，通过探测器后产生电信号，并在放大后进行快速FFT变换，最后得到运动目标相应的多普勒速度信号。在实验中，我们顺利测到了目标速度，测速精度优于2％，测量距离超过100米。该实验的成功，为下一步的测风系统打下了良好的理论和实验基础。对于全光纤测风雷达系统，同样采用连续相干探测的模式。该系统主要由窄线宽光纤激光器，收／发单元，光学收发天线，探测及高速信号处理系统等组成。与基于CO₂激光器的相干测速雷达相比，它在光源结构、激光传输、系统热管理、探测方式等方面具有优势，有利于系统的集成化、小型化，方便系统的安装和调试。作为短程测风雷达，该全光纤测风系统可通过步进电机调节来实现聚焦，完成从5米到200米距离内各点激光视线方向上的风速测量。为了测量实际大气水平风场速度和方向，在下一步的工作中将增加扫描系统，通过逐层扫描，来获得5²00米的风速分布。更多还原

【Abstract】 Laser Doppler anemometer is used to measure the speed of wind in the atmosphere based on the theory of Doppler technology. Compared with traditional technology & equipment, the laser Doppler anemometer has many advantages, such as un-perturbing of target’s moving; the signal stability; high precision; non-touch etc. So it’s used widely in meteorologic,military,aeronautic,scientific erea etc. Because of these advantages and attractive application domains, many countries and companies are developing this anemometer technology very quickly recent years, and some products have been reported in the USA, U.K., Russia,France. Laser radar is composed of laser, transmitting unit, emitter-receiver unit, detecting & signal processing unit. Actually, the system measure aerosol’s speed instead of wind’s speed, because the aerosol’s speed is equal to the wind’s speed. And after measuring the Doppler shift of scattered light, the wind’s speed can be calculated.In this work, the experiment of measuring hard target’s speed with CO₂ laser beams and the experiment of measuring speed of wind in the atmosphere with all-fiber laser system at 1.55μm are described separately. For the first one, the CO2 laser is divided into Local Oscillator （LO） and a high power beam by thin film polarization （TFP）, the last beam is transmitted to the moving target through emitter-receiver optic-antenna. And the scattered lights come back to the system through the optic-antenna mixing with LO. The light signal ,after transformed into the electric signal by the detector and amplified by the electronic unit, can be transformed to Doppler signal through FTT. The speed of hard target is measured in the experiment and the precision is up to 2%, the distance is up to 100 m. The success of this experiment supports next experiment theoretically and experientially. The CW coherent all-fiber laser Doppler anemometer is composed of fiber laser, fiber-optic circulator, optic-antenna, detector and signal processing unit. Compared with the first one, the all-fiber system has much more advantages on laser configuration, laser transmitting, cooling system, detecting mode, etc. It’s propitious to build small and robust systems. As short range radar, The all-fiber laser radar can measure in-sight wind’s speed from 5 m to 200 m. In order to measure actual wind’s speed and direction, the scan device will add to the system at the next step.更多还原