Performance of Coherent Lidar Receivers Using Atmospheric Compensation Techniques

We present recent studies on the impact of phase and amplitude fluctuations on Doppler lidars using coherent detection. As there is an emphasis on elucidating those implications of the atmospheric propagation problem that bear on the design and reliability of optical coherent lidar systems, we consider in a unified framework the effects of atmospheric turbulence and diffuse target speckle on the performance of coherent receivers utilizing atmospheric compensation techniques. As the effects ascribed to turbulence and speckle are random, and subsequently must be described in a statistical sense, we define a mathematical model for the probability density function of the received coherent signal after propagation through the atmosphere. In our model, the parameters describing the signal statistics depend on the turbulence conditions and the degree of modal compensation applied in the receiver. We provide analytical expressions and use them to study the effect of various parameters on performance, including turbulence level, signal strength, receive aperture size, speckle effective area, and the extent of compensation.