Investigation and Optimization of a Pulsed Laser Radar Transmitter for Detection Performance in a Cloud Turbulent Medium

Abstract

The performance of pulsed laser radar systems in cloud media is severely affected by turbulence. These systems should then be able to identify targets in highly turbulent media. Here, the effects of turbulence on a laser beam reaching a target are investigated using ALTM software. The precise values of the beam parameters on the target (including the effective beam spot diameter, mean intensity, scintillation index, etc.) are also calculated for different states by changing the transmitter parameters (i.e., the divergence half-angle and power) and the separation distance between the target and the laser radar system. Accordingly, appropriate corrections can be applied to the laser radar system in order to efficiently perform in turbulent media such as cloud clutter. It is found that the transmitter beam divergence half-angle should be less than 500 μrad. Under this condition, it is possible to decrease the effective laser spot diameter and the scintillation index on the target, while also increasing the spatial coherence radius of the beam and the mean intensity. Alternatively, using PCModWin software, influences of absorption and scattering of cloud clutter on the beam intensity received by a target are simulated, followed by applying corrections to the intensity. As a result, the system performance can be improved for the desired detection distance in the presence of turbulence.