China Deploys Commercial Hollow-Core Optical Fiber for AI Data Centers in Ningxia
China has commercially deployed hollow-core optical fiber across a 30-kilometer link between AI data centers in Zhongwei, Ningxia. By transmitting light through an air channel rather than solid glass, signal propagation speed reaches 99.7% of the speed of light in a vacuum, cutting transmission latency and optical loss by over 30%. High transmission latency between geographically separated data centers is a critical bottleneck for distributed AI cluster training and cross-regional compute infrastructure. This practical deployment demonstrates that hollow-core fiber can break traditional glass propagation speed limits, paving the way for ultra-low-latency, ultra-high-bandwidth interconnects in next-generation networks. The fiber measures under 0.4 mm in diameter and embeds 20 micro-glass cylinders within its inner walls to confine light within the hollow air core. Traditional solid glass fibers limit light propagation to roughly 69.5% of vacuum light speed ($c$), whereas air channels dramatically minimize optical dispersion and signal attenuation over long distances.
## BACKGROUND
Conventional optical fibers rely on total internal reflection to guide light through a dense solid glass core, which slows down light due to the material's refractive index. In contrast, hollow-core optical fibers guide light through an air-filled center using microstructured claddings, such as anti-resonant or photonic crystal structures. Because air has a refractive index close to 1, light travels nearly 44% faster than in standard glass fibers while experiencing lower non-linear interference.