Efficient Numerical Modeling of Near-Field Diffraction in ORIS-Assisted Free-Space Optical Links
It provides an efficient numerical method for analyzing near-field propagation in ORIS-assisted FSO systems, which is crucial for system design but is an incremental improvement over existing numerical techniques.
This paper proposes a fast Fourier transform (FFT)-based numerical framework for modeling near-field diffraction in ORIS-assisted free-space optical links, achieving accuracy comparable to direct Riemann-sum evaluation while significantly reducing computational complexity.
This paper investigates near-field propagation in optical reconfigurable intelligent surface (ORIS)-assisted free-space optical (FSO) communication systems. Unlike conventional far-field scenarios, near-field propagation involves complex diffraction effects that hinder tractable closed-form analysis. To address this issue, a numerical framework for evaluating the optical field distribution of ORIS-assisted FSO links is proposed. Specifically, two numerical approaches are considered: direct Riemann-sum evaluation and a fast Fourier transform (FFT)-based method. Although the Riemann sum approach provides accurate field estimation, it incurs extremely high computational complexity due to the fine spatial discretization of the ORIS surface required at optical wavelengths. To improve computational efficiency, the optical-field calculation is reformulated as a convolution in the spatial-frequency domain, enabling efficient FFT-based propagation analysis. Simulation results demonstrate that the proposed FFT-based method achieves accuracy comparable to that of the Riemann-sum approach while significantly reducing computational complexity.