Key Notes
- China Telecom and its partners demonstrated simultaneous transmission in both directions over more than a thousand kilometers of hollow-core fiber.
- The reported capacity and lower propagation delay could support stronger connections between geographically separated AI computing sites.
- The transmission demonstration is separate from existing shorter commercial routes and does not establish a matching improvement in AI training speed.
China Telecom Research Institute, optical-fiber maker YOFC and ZTE have demonstrated simultaneous two-way transmission over 1,007.48 kilometers of hollow-core fiber. The reported capacity reached 64 terabits per second in each direction, a milestone for a technology that could reduce the time needed to move data between distant AI computing centers.
China Telecom detailed the trial in a November 4 announcement, describing it as the first real-time, single-fiber bidirectional demonstration at this distance. Its combined capacity was 128 Tb/s across both directions. The result concerns a transmission system carrying many optical channels, rather than a single connection available to an individual customer.
A Thousand Kilometers in 3.43 Milliseconds
CCTV subsequently reported a one-way transmission delay of 3.43 milliseconds. China Telecom expert Huo Xiaoli said hollow-core fiber can lower latency by about 30% compared with conventional solid-core fiber. Light travels mainly through an air-filled channel, instead of the glass core used in standard fiber, shortening its journey over the same distance.
The capacity figure is equally striking. At 64 Tb/s, the nominal data rate in one direction equals eight terabytes per second, or roughly 160 files of 50 gigabytes each. That explains the comparison with transferring 160 large 4K films every second. Capacity measures how much information a link carries; latency measures how long a signal takes to arrive. Improving one does not automatically improve the other.
Making Hollow-Core Fiber Work Over Longer Distances
The partners used 800 Gb/s optical channels across the extended C and L bands. China Telecom says improvements to fiber manufacturing removed absorption caused by carbon dioxide and carbon monoxide within those bands. The system also used commercial amplifiers with conventional output power and signal compensation at the transmitter to keep performance balanced across channels.
China Telecom describes the demonstration as a point-to-point, non-loopback transmission record for hollow-core fiber. That qualification matters when comparing it with experiments that repeatedly circulate a signal through a shorter length of cable. The company presents the result as evidence that hollow-core technology can support long-distance, high-capacity backbone networks.
Why AI Infrastructure Builders Are Watching
For AI operators, the potential benefit is better connectivity between computing sites. In a technical discussion of hollow-core fiber, ZTE identifies links between AI computing centers as a key application. It also stresses the need for reliable forwarding, protection against packet loss and congestion, and appropriate network equipment to support coordinated work across clusters.
A faster optical path could reduce one component of the communication delay between sites. It does not establish that an AI training job will finish 30% sooner, or that a distant data center can perform like machines connected within the same building. ZTE also lists manufacturing capacity, standards, deployment costs and maintenance among the obstacles to wider commercialization.
Commercial deployments already exist on shorter routes. China Comservice announced in November 2025 that it had completed a 110-kilometer route between Dongguan and Hong Kong, including 100 kilometers of hollow-core cable, with a subsidiary handling the Shenzhen–Dongguan section. That project is separate from the new 1,007-kilometer transmission demonstration.
The work adds another dimension to the networking investment behind AI. Recent efforts to increase bandwidth density inside AI infrastructure address the connections around computing systems; hollow-core fiber targets the physical routes carrying information over longer distances. The next commercial test is whether its latency advantage can be delivered reliably and economically at scale.
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