# An Experimental Study on the Reflection Characteristics of Laser Echo Light Waves
## 5 Conclusions  
This paper built two return path wireless optical experimental links, carried out laser transmission experiments in the Xi'an Beilin area, analyzed the fluctuation characteristics of light intensity and light spot drift under different weather conditions and transmission distances, and specifically analyzed the scintillation index of laser echo, atmospheric refractive index structure constant, light intensity probability density distribution, and light spot centroid distribution. The experimental results show the following: (1) The scintillation index increases in the order of cloudy, heavy rain, moderate rain, light rain, and sunny conditions. The atmospheric refractive index structure constant increases with the distance of the transmission link. The turbulence measured on the 0.8 km link belongs to the weak-turbulence region, and the turbulence measured on the 4 km link belongs to the medium-turbulence region. (2) The probability density distribution of light intensity of the 0.8 km link in the measurement samples obeys the log-normal distribution, and the probability distribution of light intensity of the 4 km link obeys the Gamma-Gamma distribution on sunny, lightly rainy, and moderately rainy days. The light intensity fluctuations of the two links in different weather conditions increase in the order of cloudy, heavily rainy, moderately rainy, lightly rainy, and sunny. (3) In the two links, the drift amount of the light spot in the horizontal direction is often greater than the drift amount in the vertical direction. The horizontal direction is more significantly affected by turbulence than the vertical direction. The range of the centroid distribution of the light spot increases with the increase of the link range, and the range of the centroid distribution of the light spot increases in the order of cloudy, rainy, medium rainy, light rainy, and sunny days. The experimental results show that the accuracy of the link design and the optimized layout of the corner reflectors have a significant impact on the strength and stability of the echo signal, especially under the conditions of atmospheric turbulence and multipath effects. This study obtained the relationship between turbulence intensity, transmission distance, and weather type through dual-distance, multi-weather corner reflector array experimental measurements, providing valuable experimental data and theoretical support for future high-precision optical measurements and an optimized design of long-distance links. In this paper, the impact of changes in temperature, humidity, and wind speed on the experimental data is not accurately considered. In future studies, we plan to expand the experimental link to a longer measurement distance of 10 km or more, and consider parameters such as changes in temperature, humidity, and wind speed to explore the laser echo reflection characteristics of the corner reflector array in a richer environment. This will also bring many technical challenges, such as signal attenuation and noise interference over longer paths, the impact of atmospheric turbulence on signal stability, and further requirements for link alignment accuracy. Figure 11: Probability density distribution of the center coordinates of the light spot of Link 2. **Author Contributions:** Conceptualization, X.K. and X.L. ; Data Curation, X.K. and X.L. ; Formal Analysis, X.K. ; Funding Acquisition, X.K. and J.L. ; Investigation, X.K. ; Methodology, X.K. and X.L. ; Project administration, X.L. ; Resources, X.L. ; Software, X.L. ; Supervision, X.K. ; Validation, X.K., X.L., J.L. and R.W. ; Writing--Original Draft, X.L. ; Writing--Review and Editing, X.K., X.L., J.L. and R.W. All authors have read and agreed to the published version of the manuscript. **Funding:** This study was funded by the National Natural Science Foundation of China [No. 61377080]; the Special Research Program of the Shaanxi Provincial Department of Education [22]K0530]; the Xi'an Science and Technology Plan Project [No.