امير دانشمندكشاورز

Propagation of electromagnetic waves in turbulent media, particularly across the air–water interface, is considered one of the important an‎d challenging topics in optical physics an‎d photonic engineering, playing a key role in the performance of systems such as free-space optical communications, underwater optical communications, marine LiDAR, an‎d remote sensing systems. Turbulence an‎d roughness of the water surface, mainly induced by wind an‎d surface wave fluctuations, introduce statistical distortions to the optical wavefront, leading to phenomena such as beam deflection, beam centroid displacement, an‎d fluctuations in the received signal intensity. These effects can result in reduced imaging accuracy, degradation of the signal-to-noise ratio, an‎d increased bit error rates in optical systems propagating across the air–water interface. In this study, the propagation of visible-spectrum electromagnetic waves through a turbulent atmospheric medium an‎d across a wavy air–water surface into the aquatic environment is numerically simulated an‎d analyzed based on experimental data. To this end, the turbulent water surface is first reconstructed using laboratory measurements an‎d image processing techniques. By extracting the displacement field of image points an‎d calculating the local surface slopes, a continuous three-dimensional model of the instantaneous water surface topography is generated, accurately representing the realistic behavior of surface waves under various wind conditions. This model is employed as the air–water interface in the optical simulations. Subsequently, the propagation paths of optical rays are simulated using the ray-tracing method based on the classical laws of reflection an‎d refraction. For each ray, the angle of incidence, local surface normal vector, refraction angle, an‎d reflection angle are calculated, an‎d the influence of surface turbulence on beam deviation is statistically investigated. Moreover, the probability density functions of the refraction an‎d reflection angles are extracted, an‎d their dependence on parameters such as wind speed an‎d wind direction is analyzed. The results indicate that increasing surface turbulence intensity significantly enhances the angular spreading of the rays an‎d intensifies fluctuations in the received signal. Finally, the numerical simulation results are compared with experimental data, showing good agreement an‎d thereby validating the proposed model. The simulation framework developed in this research provides an efficient tool for the quantitative analysis of surface turbulence effects on optical wave propagation an‎d can be utilized in the design an‎d optimization of underwater optical communication systems, marine LiDAR, an‎d optical systems operating across the air–water interface.

پردازش تصوير , ارتباطات نوري زيرآب , نرخ خطاي بيت , شبيه سازي تجربي , اثرات موج سطحي روي آب

Image Processing , Underwater Optical Communications , Bit Error Rate (BER) , Experimental Simulation , Effects of Surface Waves on Water

Amir Daneshmand Keshavarz

Fatemeh Dabagh Kashani