Optimization And Experimental Research On All-fiber Coherent Wind Lidar

Atmospheric wind velocity detection research has widely affected industry and scientific research and other related fields.In view of its economic value and social significance,it has become a research hotspot.Compared with other wind velocity detection equipment,the coherent wind lidar system with laser as the detection light source has both higher temporal and spatial resolution and higher measurement sensitivity.And lidar can work under various weather conditions,which has been widely applied in many areas including wind power generation,climate change forecast,aviation safety,and launching of rockets.In this thesis,a study of coherent lidar for wind velocity measurement is undertaken.A continuous wave coherent wind lidar system is established.The specific research work is described as follows:(1)Based on the principle of coherent wind lidar and the lidar equation,the carrier-to-noise ratio in both continuous wave lidar and pulse lidar is analyzed,and the key parameters affecting the carrier-to-noise ratio are given: antenna efficiency and local oscillator optical power.The antenna efficiency is an important parameter that reflects the strength of the backscattered signal received by the lidar system to detect the target;the optical power of the local oscillator is the main reason for the shot noise and the relative intensity noise.The relationship between the antenna efficiency and the truncation ratio and the relationship between the carrier-to-noise ratio and the local oscillator power are then analyzed.(2)Based on the theoretical analysis results,the parameters of the seed laser,the amplifier,the balanced photodetector,i.e.,were optimized.An all-fiber continuous wave coherent wind lidar system is established.The weight function of the wind velocity signals at different directions from the lidar is analyzed.A vari-focusing optical telescope with the focusing distance range from 5 m to 200 m is designed and fabricated according to the result of the weight function.The parameters of other main components in the lidar are also introduced.(3)The coherent wind lidar is tested by different targets including rotating disk,vapor and wind velocity in atmospheric environment.The result of the rotating turntable experiment is that a linear fit is achieved between the lidar measurement result and the disk rotation speed,and the correlation coefficient between the two sets of data is above 0.993.In the experiment of wind velocity measurement under atmospheric environment conditions,the measurement result is basically consistent with the actual situations.Experiments show that the performance of lidar system is good.