# An Experimental Study on the Reflection Characteristics of Laser Echo Light Waves  
[PERSON]  
1 Faculty of Automation and Information Engineering, Xi'an University of Technology, Xi'an 710048, China; [EMAIL_ADDRESS] (X.L. ); [EMAIL_ADDRESS] (J.L. ); [EMAIL_ADDRESS] (R.W.) [PERSON]  
1 Faculty of Automation and Information Engineering, Xi'an University of Technology, Xi'an 710048, China; 2220321174@aaut. the beach, and on the road. They also conducted experimental measurements on the characteristics of beam drift and spot expansion [5]. In 2018, [PERSON] and others designed a laser detection imaging experiment on a return path. By observing the complete far-field laser spot in Hefei, they conducted a statistical analysis of the light intensity distribution characteristics in the image. By fitting the method, they obtained the ideal point scintillation index of the center of the spot and then inferred the value of the turbulent refractive index structure constant and the atmospheric coherence length [6]. In 2021, [PERSON] built a laser transmission experiment with a transmission distance of 2.5 km in Xi'an. Through the light intensity images recorded at the receiving end, he used the scintillation method to calculate the atmospheric refractive index structure constant in Xi'an city during the experimental period. He also compared and analyzed the changes in atmospheric turbulence at night under three weather conditions, sunny, cloudy, and hazy, as well as the statistical characteristics of the light intensity scintillation of the laser beam [7]. In 2021, [PERSON] conducted an experimental study on the impact of atmospheric turbulence on the link performance of free-space optical communication systems over South Africa, analyzing the Rytov variance, logarithmic irradiance, signal-to-noise ratio, bit error rate, fading loss, and power flicker index at different wavelengths under weak-turbulence conditions [8]. In 2022, [PERSON] designed a turbulence simulation device using thermal resistors and fans and built an indoor experimental system for laser transmission. He studied the intensity distribution of the laser wavefront through experiments and analyzed the relationship between the beam drift and intensity fluctuations at four wavelengths with temperature and wind speed [9]. In 2022, [PERSON] and others regarded the scintillation effect as multiplicative noise in the transmission of optical communication systems, derived a multiplicative noise model for atmospheric turbulence, and conducted experimental measurement research [10]. In 2023, [PERSON] and others built a laser active-illumination beacon atmospheric coherence length measurement system based on 3M reflective film, realizing the detection system's single-end configuration of transceiver integration. The atmospheric coherence length was measured by switching between active illumination beacons and traditional 650 nm laser beacons [11]. In 2024, [PERSON] et al. derived an expression for the variance in the drift angle of a beam under deep turbulence conditions. A return path laser imaging detection system was built, and echo images and the atmospheric coherence length of the laser spot at different times on the 1 km and 7 km transmission paths were experimentally obtained. The results showed that the drift angle mean-square error and the atmospheric coherence length have obvious periodicity over time, and the two change synchronously, but with opposite trends [12]. Although the impact of atmospheric turbulence on laser transmission has been widely studied, existing results still have two major limitations. Most experiments are limited to a single transmission distance, and there is a lack of comparative analysis of long- and short-distance links, resulting in the lack of a quantitative model for the variation in turbulence intensity with distance. Existing studies usually assume static meteorological conditions and ignore the compound effects of multiple weather conditions on link stability in actual environments.