Study on the propagation performance of OAM-hopping in atmospheric turbulence channel

Free space optical communication (FSO) is susceptible to atmospheric turbulence, which greatly affects the practical application of atmospheric laser communication. In this paper, we explore a simple and effective anti-atmospheric turbulence technique based on the feasibility study of orbital angular momentum beam (OAM) hopping. Different modes of OAM beams with distinct topological charges are sequentially transmitted within a symbol period to achieve diversity gains by ensuring orthogonality among them and varying spatial paths. The transmission characteristics of OAM beams in atmospheric turbulence are analyzed, and an intensity modulation/direct detection (IM/DD) FSO model is established under the Gamma-Gamma atmospheric turbulence channel. By comparing the power fluctuation and bit error rate (BER) of the communication system employing OAM-hopping with single-mode beams system, the effects of mode spacing and the number of mode hopping on the turbulence resistance capability of the OAM-hopping mechanism are investigated. Simulation results demonstrate that, under moderate turbulence conditions (𝐶_n² = 1 × 10⁻¹³), using the mode set {+1, +3, +5} for OAM-hopping transmission reduces the power fluctuations and BER by approximately 10.6% and 20.1%, respectively, compared to the system using only a single-mode beam for transmission. The research findings validate the feasibility and effectiveness of OAM mode-hopping technology for turbulence-resistant applications in FSO, providing an important technical approach to enhance the performance of FSO systems in atmospheric turbulence.