# Non-Classic Atmospheric Optical Turbulence: Review
## 6 Influence in Applications
### LIDARs  
Light detection and ranging systems (LIDARs) are currently used in various applications from meteorology to headlight sensing. In these systems, light must travel through the same medium twice, either through exactly the same path (mono-static case) or along slightly different paths (bi-static case). In the former case, the phase conjugation phenomenon considerably complicates the analysis, producing intensity redistribution in the region around the optical axis. This phenomenon is known as enhanced back-scatter (EBS), and is positive for retro-reflector targets and negative for flat mirror targets. While double-passage propagation of laser beams were thoroughly investigated for Kolmogorov turbulence [95; 102] a more complex case of non-Kolmogorov turbulence was not fully explored until recently. The seminal analysis of LIDARs in weak non-Kolmogorov turbulence was made in [103], revealing how a power law different from [PERSON]'s impacts the average intensity distribution, the long-term spread and the scintillation index of an optical beam after it passes through turbulence to a (smooth) target surface, interacting with such a target and passing back through the same turbulent channel. Such an analysis was conducted for both mono-static and bi-static configurations. In the case of the mono-static  
Figure 20: Mean BER as a function of mean SNR for several sets of anisotropy factors (shown as \(z_{x}\)eff and \(z_{y}\)eff in the legend) with \(\alpha\)= 3.2. Reprinted with permission from Reference [100].  
channel, the enhanced backscattering effects were also investigated. Both the analytical results and those based on wave-optics simulation were obtained and compared.  
The double-passage problem of a laser beam propagating in the presence of non-Kolmogorov atmospheric turbulence at any turbulence strength was analyzed in Reference [104]. In particular, using the extended Rytov theory, for the horizontal path, the authors theoretically investigated the scintillation index of a Gaussian beam reflected from a small unresolved target in deep turbulence conditions. The authors theoretically showed that different power laws substantially affect the scintillation results; however, they did not observe the scintillation peaks predicted by the theory near the focusing regime, using wave optics simulations. In addition, authors showed that the occurrence of giant intensity spikes previously discussed in Section 2.4 is currently not captured by the theory. The numerical outcomes for the scintillation index in mono-static and bi-static cases, at any turbulence strength, are shown in Figures 21 and 22, respectively. Finally, we show in Figure 23 the EBS factor appearing in the mono-static LIDAR scenario, as a function of the square root of the Rytov variance for several power law values [104].  
Figure 21: Mono-static case: scintillation index as a function of the square root of the Rytov variance for several power law values. Reprinted with permission from Reference [104].  
Figure 22: Bi-static case: scintillation index as a function of the square root of the Rytov variance for several power law values. Reprinted with permission from Reference [104].