Research on enhancing received power in free-space optical links by illuminated auxiliary reflecting surface: analysis and optimization

To address the problem of insufficient power utilization caused by the receiving aperture being smaller than the far-field beam spot in free-space optical (FSO) communication, a power collection architecture based on an auxiliary reflecting surface (ARS) is proposed to enhance the received optical power. A system model incorporating far-field Gaussian beam propagation and geometric optical reflection is constructed to derive theoretical expressions for the constraints on ARS deployment. Considering practical scenarios in which the ARS is only partially effectively illuminated by the beam, a closed-form expression for the power gain is further obtained by using a projection-based dimensionality reduction and approximation approach. Based on the derived expression, we formulate and solve the optimization problem for the ARS deployment to maximize power gain. A zero-gradient with margin constraints (ZGMC) algorithm is proposed to determine its optimal position and orientation. The accuracy of the optimal placement solution is validated through simulation. An equivalent experiment is conducted to verify the feasibility and effectiveness of the ARS. The experimental results show a consistent trend with the simulation, confirming the validity of the proposed method. This study offers valuable insights into the optimization of practical FSO systems.