相干激光雷达中望远镜的优化及探测性能分析

Optimal Design of the Telescope in Coherent Lidar and Detection Performance Analysis

利用脉冲能量为110μJ、重复频率为20 k Hz及脉冲宽度为300 ns的光纤激光器设计了一套工作波长为1.55μm的相干测风激光雷达,给出了系统的性能参数。根据后向传播本振的原理计算出当望远镜对发射高斯光束的截断比为最优值0.823时,激光雷达的天线效率达到最大值0.422。在最优截断比条件下分析了望远镜口径对相干激光雷达载噪比的影响,优化了望远镜设计。从理论上计算出激光雷达的探测性能指标:探测距离大于3 km,风速测量范围为±62 m/s,距离分辨率为84 m,风速测量精度优于0.1 m/s,时间分辨率为0.5 s。

A fiber laser with pulse energy of 110 mJ, pulse repetition frequency of 20 kHz and pulse width of 300 ns is employed to develop the coherent lidar for wind sensing at 1.55 mm. The specifications of the main components employed to assemble the lidar are listed. By taking the advantage of the principle of backpropagated local oscillator（BPLO）, the optimal truncation ratio of the telescope is calculated. The result shows that the optimal antenna efficiency of 0.422 is obtained when the truncation ratio arrives at 0.823. The effect of the aperture of the telescope on the carrier-to-noise ratio（CNR） of the coherent lidar is analyzed on the condition of the optimal truncation ratio. The design parameters of the telescope are optimized. The performance of the lidar is theoretically calculated and listed as follows： detection range is longer than 3 km;wind velocity range is ± 62 m/s; range resolution is 84 m; wind velocity accuracy is better than 0.1 m/s; time resolution is 0.5 s.