Vision transformers motivating superior OAM mode recognition in optical communications

Abstract

Orbital angular momentum (OAM) has recently obtained tremendous research interest in free-space optical communications (FSO). During signal transmission within the free-space link, atmospheric turbulence (AT) poses a significant challenge as it diminishes the signal strength and introduce intermodal crosstalk, significantly reducing OAM mode detection accuracy. This issue directly impacts the performance of OAM-based communication systems and leads to a reduction in received information. To address this critical bottleneck of low mode recognition accuracy in OAM-based FSO-communications, a deep learning method based on vision transformers (ViT) is proposed for what we believe is for the first time. Designed carefully by numerous experts, the advanced self-attention mechanism of ViT captures more global information from the input image. To train the model, pretraining on a large dataset, named IMAGENET is conducted. Subsequently, we performed fine-tuning on our specific dataset, consisting of OAM beams that have undergone varying AT strengths. The computer simulation shows that based on ViT method, the multiple OAM modes can be recognized with a high accuracy (nearly 100%) under weak-to-moderate turbulence and with almost 98% accuracy even under long transmission distance with strong turbulence (C N 2=1×10−14). Our findings highlight that leveraging ViT enables robust detection of complex OAM beams, mitigating the adverse effects caused by atmospheric turbulence.

Top three intelligent algorithms for OAM mode recognitions in optical communications

“…From introduction of OAM shift keying-based optical communication system where novel phase hologram for multiplexing and demultiplexing OAM states significantly improve the system performance, to employing adaptive demodulation technique using an improved CNN architecture to yield high demodulation accuracies, all showcasing the CNN model's robustness and generalization capabilities [54,115]. Advantages such as the need for a small pixel-count imager to record the OAM multiplexed signal, outperforming KNN, NBC, and BP-ANN in strong ATs, better BER performance, fast speed, good generalization ability, and superior robustness are very promising for the future of FSO-OAM communications [133,134].…”

Research Progress on Router Devices for the OAM Optical Communication

“…For a mature OAM optical communication system, the manipulation and transformation of different channels play a crucial role in enhancing the flexibility and practicality of the system [83][84][85]. Currently, the research focus in OAM optical communication lies in the development of routing technology that enables end-to-end signal transmission path transformations [86][87][88][89][90][91]. Therefore, extensive research and development have been conducted on the OAM router devices (OAM-RDs) with significant performance enhancements [92][93][94].…”