Signal-to-noise Ratio of Heterodyne Lidar Systems in the Presence of Atmospheric Turbulence

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Abstract
A general expression for the signal-to-noise ratio of a heterodyne lidar system in the presence of atmospheric turbulence is derived which is valid in both the near and far fields of the laser and remote scattering source. We consider the situation where a laser transmitter directs an optical beam at some remote scattering region of interest. The back-scattered light is collected by a receiving aperture and mixed with a suitable coherent local oscillator reference field. Both coaxial and bistatic lidar systems are considered. In both cases we are able to obtain algebraic expressions for the signal-to-noise ratio which are valid for an arbitrary propagation path through the atmosphere. Numerical results are presented for both a 3·7 and a 10·6 w m lidar system. Additionally, we obtain the conditions under which atmospheric turbulence will severely limit the performance of meterodyne lidar systems.