Nonprobe Adaptive Compensation for Optical Wireless Communications Based on Orbital Angular Momentum

With the continuous growth of network traffic, optical wireless communication (OWC) technology based on orbital angular momentum (OAM) can meet the needs of large-capacity modern communication and is an effective way to substantially increase wireless information transmission capacity. However, the OAM beam distortion caused by atmospheric turbulence in the actual link and the limitations caused by phase singularities are major challenges faced by the OAM-OWC system. In this paper, we address these issues and propose a low-complexity nonprobe adaptive optics (AO) compensation technique based on Y-net which can achieve high-accuracy distortion compensation and OAM mode demodulation simultaneously. In this approach, only one CCD is required for the Y-net-aided AO (Y-net AO) technique without a traditional probe path while satisfyingly balancing OAM-based optical transmission system complexity and transmission performance. Extensive simulations show that the proposed Y-net-aided AO technique can indeed decontaminate distorted OAM beams in both single- and multiplexed-channel OAM links. Furthermore, a noise model is established to analyze the robustness of the Y-net AO technique. The Y-net AO technique exhibits less system complexity and better anti-noise performance than the ordinary convolutional neural network (CNN)-based AO scheme. In summary, Y-net AO technology for OAM-OWC systems with high correction accuracy and low structural complexity is considered for effectively improving the transmission performance in this paper. Key AO technologies for the high-quality and innovative development of large-capacity communications are also expected to be formed.