China has successfully tested hollow-core fiber over 626 miles (1,007.5 kilometers), reducing signal transmission delays by approximately 30% compared with conventional solid-core optical fiber. The experiment was conducted jointly by the China Telecom Research Institute, fiber manufacturer YOFC, and telecommunications equipment company ZTE. The development could help meet growing demand for faster data transmission between data centers, particularly as artificial intelligence (AI) and cloud computing continue to expand.Hollow-core fiber and low-latency transmissionThe main difference between hollow-core and conventional optical fiber is the material used to guide light. Traditional fiber uses solid glass, while hollow-core fiber guides light through a microscopic channel filled primarily with air. Since light travels faster through air than through glass, this design can reduce transmission delays over long distances. As the South China Morning Post (SCMP) reported, the technology replaces the solid glass core with air, cutting the data transmission delay by about 30 percent over 621 miles. Light travels at approximately 186,411 miles (300,000 kilometers) per second in a vacuum, compared with around 124,274 miles (200,000 kilometers) per second in conventional glass optical fiber.Over 621.4 miles (1,000 kilometers), the hollow-core system recorded a one-way transmission delay of approximately 3.4 milliseconds, compared with about 5 milliseconds for conventional solid-core fiber. This represents a roughly 30% reduction in transmission latency. The experimental link achieved a transmission capacity of 64 terabits per second in each direction, giving it a combined bidirectional capacity of 128 terabits per second. Theoretically, this is equivalent to transferring approximately 160 4K movies per second in each direction, assuming each movie is 50 GB.Researchers assembled the 626-mile link using more than 300 fiber spools, each measuring between 1.24 and 3.1 miles (2 and 5 kilometers). They also used commercial optical amplifiers and signal pre-equalization techniques to reduce optical losses and interference and maintain stable transmission.Potential benefits for AI data centersThe experiment comes as China expands its computing infrastructure through the East Data, West Computing initiative, launched in 2022. The program aims to connect computing resources in western China with demand centers in the east. It includes eight national computing hubs and 10 data center clusters across regions such as Inner Mongolia, Guizhou, Gansu, and Ningxia.By the end of 2025, China had established 145 backbone fiber links, with network latency targeted at below 20 milliseconds. Hollow-core fiber could improve connections between distant computing facilities. This is particularly important for AI data centers, where servers exchange large volumes of information to train and run AI models.YOFC chief scientist Wang Ruichun also highlighted the importance of low-latency optical connections for meeting the demanding communication requirements of AI data centers. The technology is already being explored beyond laboratory research. More than 10 commercial and pilot projects have reportedly been undertaken across Asia and Europe, including a hollow-core fiber connection supporting financial communications between Shenzhen and Hong Kong. However, the 626-mile achievement was a controlled experiment, not nationwide commercial deployment. Wider adoption will require further improvements in transmission stability, optical losses, amplification technology, and compatibility with existing networks.