Research On 1550 Nm All-Fiber Coherent Laser Wind Lidar Technology

The monitoring wind speed has very important applications in weather forecasting,aircraft safety and wind resource assessment.The wind lidar has very high detection sensitivity and space-time resolution in wind speed remote sensing,and has been widely used in atmospheric wind field,atmospheric wind profile and wind turbine wake detection,as well as dangerous airflow warning.The light in the 1550nm band is just in the eye-safe of the human eye and does not pose a threat to the safety of the human eye.In this paper,a 1550nm all-fiber coherent wind lidar is built based on fiber laser and 1550nm fiber optic device.The coaxial optical structure is used,that is,both transmitting and receiving are on the same optical path.The all-fiber structure is beneficial to the stability of the system,making the system The structure is more compact and flexible to assemble.Firstly,the paper introduces the design principle of coherent laser wind radar,discusses the principle of coherence detection,wind field vector inversion,analyzes the coaxial and off-axis forms of laser wind radar formula,and discusses the coaxial Factors affecting signal-to-noise ratio under off-axis conditions;the definition of wind speed resolution and range resolution is studied,which provides a theoretical basis for determining wind speed resolution and range resolution.Secondly,based on the experimental principle of wind radar,a coaxial all-fiber coherent wind lidar is designed and built.The coaxial all-fiber coherent wind lidar consists of three parts:1 lidar launch system:1550nm fiber laser There are two outputs,one is used as reference light,the other is modulated by the acousto-optic modulator after optical amplification;2 Optical antenna unit:consists of a telescope,the main fiunction is to emit laser light and collect scattered light to the optical fiber;3 data Processing unit:The coherent beat signal is acquired by GAGE's ultra-high speed acquisition card.Finally,an experimental study based on the established coherent wind lidar system was carried out.In order to verify the detection accuracy and accuracy of the system,the following work was carried out:(1)Ranging experiments on wall hard targets 70 meters away,the reflected signals obviously have obvious time gaps in the time domain,which is better verified.The accuracy of the system's ranging.(2)In order to make the system perform the speed measurement experiment well and to calibrate the system speed,a set of rotary hard target speed measuring device based on variable speed is established,and the mechanical rotation is measured by the Doppler frequency shift formula.The edge tangential speed of the runner at different speeds has a correlation with the actual speed of the runner of 0.9958.(3)In order to be able to measure the actual atmospheric wind speed,the wind speed measurement was performed using a water vapor spray device,and the wind speed of the spray device was measured using the backscattered light of the water vapor.(4)The wind speed under actual atmospheric conditions is measured.The measured wind speed frequency shift is=3.5MHz,and the actual atmospheric wind speed is calculated to be 2.7m/s,which is completely consistent with the measured result of the anemometer.