# Experimental Study on Phase Scintillation of Optical Transmission in Atmospheric Turbulence
## 1 Introduction  
Optical wireless communication systems have become a critical direction for the future of communication systems due to their advantages of high bandwidth, no spectrum limitation, and high security. However, since optical wireless communication systems need to transmit information through the atmosphere, atmospheric turbulence significantly affects the propagation of light waves, particularly the disturbance of wavefront phase, which is one of the key factors limiting performance [1]. [PERSON] [2] proposed a method to measure wavefront phase disturbances and characterize atmospheric turbulence by directly using wavefront slope measurements from a Hartmann wavefront sensor. This method does not assume data homogeneity and isotropy, avoiding complex wavefront phase reconstruction.  
[PERSON] [3] proposed a method based on polar coordinates and logarithmic spectrum sampling to directly measure the slope of the Shack-Hartmann wavefront sensor (SH-WFS). This method considers the spatiotemporal statistical characteristics of the slopes, effectively generating optical turbulence slopes that conform to theoretical statistical properties. [PERSON] [4] proposed a new adaptive optics closed-loop control algorithm that combines the Zernike modes of a fast steering mirror (FSM) and a deformable mirror (DM) to improve the accuracy and range of wavefront correction. The relationship between the degree of wavefront distortion and atmospheric turbulence intensity, as well as the proportion of wavefront tilt components and turbulence intensity, was analyzed. [PERSON] [5] used deep-learning techniques to estimate the missing information at the bad spots detected by the wavefront sensor in adaptive optics systems, thereby reducing the reconstruction error of distorted wavefronts. [PERSON] [6] proposed a model for the wavefront phase relationship of dual-wavelength Gaussian beams under weak turbulence conditions and suggested methods for compensating and correcting wavefront distortion differences. [PERSON] [7] proposed a wavefront distortion correction method based on Zernike polynomial coefficients, which can effectively improve the accuracy of adaptive optics correction. This method has been validated through numerical simulations and experiments under strong turbulence conditions, significantly improving the correction accuracy of signal and beacon wavefronts. [PERSON] [8] proposed and experimentally verified a bi-directional WDM-FSO transmission system integrated into a PON network for wireless traffic and achieved a 1000 m free-space transmission length based on a practical power budget for each FSO signal. [PERSON] [9] developed a low-cost FSOC device with high bandwidth and stable data transmission. The FSOC device was also experimentally verified to be able to maintain a stable connection with high bandwidth over a distance of 1.4 km, which provides new possibilities for the development of future communication technologies.  
This study aims to investigate the specific impact of atmospheric turbulence on the wavefront phase under different weather conditions and transmission distances through theoretical analysis and experimental measurements, revealing its variations under different environmental conditions. Three experimental links were established, and the Shack-Hartmann wavefront sensor was used to precisely measure the wavefront phase affected by atmospheric turbulence. Wavefront distortions were analyzed and compared using peak-to-valley values, root mean square (_RMS_) values, and the mean square error (MSE) of wavefront distortions. Local distortions were visually observed using Gaussian curvature images and their positive and negative curvature peaks. Finally, the study explored wavefront distortions under different wavelengths and temperatures, aligning with theoretical predictions.