OWC4DT: a 25 Gbps Plug-And-Play Self-Alignment Optical Wireless Communication System for Distributed Training in Data Center

Recently, the development of foundational models with massive parameters has increasingly relied on distributed training frameworks, which require synchronization of parameter gradients across multiple GPUs, raising the demand for high-speed interconnects within GPU clusters. Although highbandwidth interconnect technologies like NVLink and InfiniBand support these distributed frameworks, they rely on wired media, leading to high cabling complexity and maintenance costs for large-scale data centers. To establish flexible and scalable data centers, Optical Wireless Communication (OWC) technology has emerged as a promising alternative to replace wired media. Most existing studies adopt the Fiber-Wireless-Fiber OWC (FWF-OWC) architecture, using custom-designed optical components for transceiver alignment and advanced techniques like wavelength division multiplexing (WDM) and high-order modulation to enhance communication rates. However, these systems are costly, require custom optical equipment, and have limited compatibility with optical modules. Additionally, current studies mainly conduct offline testing to measure physical-layer peak rates rather than real-time, end-to-end IP-level transmission rates, limiting practical applicability. To address these issues, we propose a minimalist FWF-OWC self-alignment system. This system performs alignment using a camera and a dualaxis stepper motor rotation platform, while being compatible with off-the-shelf SFP28 optical modules. Experimental results demonstrate that our system provides stable, plug-and-play IPlevel connectivity over a 2 -meter distance within a 10 -degree field of view, achieving TCP and UDP transmission rates of 24.2 Gbps and 25.0 Gbps, respectively. Additionally, our system also maintains an alignment tolerance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\pm} \mathbf{0. 2}$</tex> degrees at a distance of 2 meters, highlighting the potential for further cost reduction in the alignment mechanism.