# An Experimental Study on the Reflection Characteristics of Laser Echo Light Waves
## 4 Analysis and Discussion  
### Flicker Index Under Different Weather Conditions  
In practical applications, the lower the scintillation index value, the better the atmospheric transmission conditions and the higher the transmission stability of the optical signal. The experimental team conducted multiple experiments on two experimental links, a 0.8 km return path and a 4 km return path, and carried out laser transmission tests on sunny days, snowy days, light rain days, moderate rain days, heavy rain days, and cloudy nights. The definitions of rainy days are as follows: a lightly rainy day has 12 h precipitation of 0.1 to 9.9 mm, a moderately rainy day has 12 h precipitation of 10.0 to 14.9 mm, and a heavily rainy day has 12 h precipitation of 15.0 to 29.9 mm. The relevant test link conditions and flicker index data are listed in Tables 1 and 2, respectively. The table records the temperature, wind speed, and AQI (Air Quality Index).  
It can be seen from the flicker index of the measurement samples in Tables 1 and 2 that the flicker index of the 0.8 m link measurement samples T1-T12 fluctuates randomly between 0.1-0.4, and the flicker index of the 4 km link measurement samples T13-T22 fluctuates randomly between 0.2-0.6. Therefore, the light intensity distribution of the 0.8 km link is weakly fluctuating, the light intensity distribution of the 4 km link exhibits medium fluctuation, and the flicker index increases with an increase in the transmission distance. At the same time, in the samples measured by Link 1, the flicker index on sunny days, snowy days, light rain days, and moderate rain days is significantly higher than  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Measuring** & & **Time** & **Weather** & **Temperature\({}^{\circ}\)C** & **Wind Speed m/s** & **AQI** & **Humidity** & **Flicker Index** \\
**Samples** & & & & & & & \\
**T1** & 11 March 2024 & Sunny & 3–21 & 1.1–1.5 & 63 & 10.9\% & 0.362 \\
**T2** & 21 March 2024 & Sunny & 11–21 & 0.5–1.2 & 96 & 27.6\% & 0.392 \\
**T3** & 15 January 2024 & Snowy & 0–1 & 2.1–3.0 & 112 & 47.7\% & 0.326 \\
**T4** & 16 January 2024 & Snowy & 0–1 & 1.1–2.0 & 94 & 38.6\% & 0.298 \\
**T5** & 24 March 2024 & Lightly rainy & 10–12 & 0.8–1.4 & 49 & 68.6\% & 0.264 \\
**T6** & 1 April 2024 & Lightly rainy & 14–24 & 0.5–1.5 & 83 & 75.6\% & 0.283 \\
**T7** & 29 April 2024 & Moderately rainy & 11–21 & 0.5–1.2 & 47 & 68.6\% & 0.322 \\
**T8** & 8 July 2024 & Moderately rainy & 22–26 & 0.6–1.2 & 19 & 72.7\% & 0.256 \\
**T9** & 16 July 2024 & Heavily rainy & 24–27 & 0.8–1.2 & 39 & 84\% & 0.182 \\
**T10** & 7 July 2024 & Heavily rainy & 23–26 & 1.0–1.5 & 38 & 87.1\% & 0.164 \\
**T11** & 13 March 2024 & Cloudy & 5–15 & 1.2–1.5 & 72 & 20.6\% & 0.144 \\
**T12** & 31 March 2024 & Cloudy & 13–28 & 0.5–1.0 & 91 & 34.4\% & 0.188 \\ \hline \end{tabular}
\end{table}
Table 1: Experimental weather conditions and scintillation indexes of Link 1 samples T1–T12.  
that on heavy rain days and cloudy days. In the samples measured by Link 2, the flicker index on heavy rain days is also the lowest, followed by cloudy days, and the flicker index on sunny days is significantly higher than that in other weather conditions. Under the same weather conditions, the scintillation index will be lower in data samples with higher humidity.