CAICT's Ao Li: New Optical Fibers Empower AI Computing Networks

C114, September 11 (Ai Si) — New optical fiber technology has become a key variable in determining the efficiency and cost of intelligent computing infrastructure, and is on the eve of large-scale deployment.

During the 27th China International Optoelectronic Exposition (CIOE) held in Shenzhen this week, C114 and CIOE jointly hosted the "AI + New Optical Fiber Application Forum" under the theme "Light Enables Intelligence, Fiber Connects the Future," focusing on core topics including high-density optical interconnect for AIDC, hollow-core fiber, G.654.E backbone deployment, testing, and operations and maintenance.

Ao Li, vice president of the China Academy of Information and Communications Technology (CAICT), delivered a keynote speech at the forum on new optical fiber technology standards and industry progress. "Optical fiber use in AI computing centers can reach 5-10 times that of traditional data centers, making it a new engine of industry growth," he said. He noted that the ultra-high density, ultra-large capacity and ultra-low latency requirements of intelligent computing interconnection demand all-round breakthroughs in fiber performance across integration, transmission performance and other dimensions, with technological innovation accelerating.

According to CRU data, global cloud data center optical cable demand is expected to exceed 100 million fiber-km in 2026. In the first half of the year, the total length of optical cable lines nationwide reached 76.12 million km, up 3.2% year on year, while China's exports of preforms, fibers and cables saw both volume and price increases.

Notably, the demand mix is shifting: in the domestic market, demand for optical fiber from emerging application scenarios such as data centers and drones is growing rapidly, while the share of demand for traditional telecom optical cable continues to decline. The construction of intelligent computing centers has become the core driver of optical fiber demand growth — and advances in technology, pilots, standards and architecture are gathering pace accordingly.

Technology evolution: multimode, single-mode, multicore and hollow-core — multiple paths in parallel

AI computing infrastructure places stringent demands on optical fiber: ultra-high interconnect density, ultra-high-speed large capacity, and ultra-low transmission latency. Fiber core counts per rack can reach the thousand-core level, optical channel bandwidth is evolving toward 800Gbps, 1.6Tbps and higher rates, while ultra-low latency directly determines the efficiency of distributed AI training and inference response speed.

Demand structures are diverging accordingly. By distance, there are three tiers: intra-rack interconnect (scale up, under 10 meters), multi-rack interconnect within the data hall (scale out, 10 meters to 2 kilometers), and inter-cluster interconnect (scale across, over 2 kilometers). Each has different requirements, and the traditional one-fiber-fits-all approach is no longer viable.

"New optical fiber is the critical infrastructure underpinning AI computing centers. Technologies continue to iterate to meet demands for high-density interconnect, low-latency transmission and long-haul networking, with multimode, single-mode, multicore and hollow-core fiber developing in parallel to build a high-speed, efficient and highly reliable physical transmission foundation for computing networks," said Ao Li.

On technology roadmaps, he also outlined the clear positioning of four fiber types: multimode fiber supports short-reach, high-speed interconnects within data halls and between racks at low cost and high coupling efficiency; single-mode fiber remains the benchmark for long-haul, high-speed transmission efficiency; multicore fiber boosts integration through space-division multiplexing; and hollow-core fiber breaks through the performance limits of solid-core fiber with a novel structure.

Specifically, for 800G and above short-reach optical modules, VCSEL thermal drift has driven adoption of enhanced multimode fiber, and all major vendors already offer corresponding products. High-density cabling and bend-resistance requirements are shifting some capacity toward G.657 fiber, with G.657A1 and G.657 A2 seeing the strongest demand growth, together accounting for more than 20% overall.

On the long-haul side, single-mode fiber is positioned as the preferred choice for medium- and long-distance transmission. G.652.D fiber continues to be optimized toward ultra-low loss and remains the mainstream fiber for large-scale long-haul trunk deployment, while G.654.E fiber has become the preferred option for backbone long-haul and metropolitan optical transmission system deployments. Solid-core single-mode fiber supports high-capacity C+L multiband transmission, exceeding 400Tb/s over short distances and over 100Tb/s over thousand-kilometer spans. Its application scenarios have also extended from inter-data-center links to within AI computing centers, directly supporting 800G/1.6T ultra-high-speed optical interconnects in AI computing centers and enabling metropolitan and inter-provincial computing resource scheduling.

Meanwhile, the optical transmission capacity of multi-core fiber continues to rise, with technical maturity steadily improving as the technology moves from application exploration into a new phase of engineering deployment. Multi-core fiber, with 2 to 24 cores and a 125-micrometer cladding design, is compatible with existing networks, can save 40%-70% of installation space, and can deliver transmission capacity on the Pbit scale. Live network verification has already been completed. Demand for multi-core fiber is expected to exceed 2.7 million fiber-km by 2030, largely reusing existing single-mode fiber manufacturing capacity.

Demand scenarios for hollow-core fiber are also expanding. With advantages such as low latency, low loss and low nonlinearity, it is rapidly enabling high-value applications including data center interconnects, high-frequency financial trading and long-haul transmission. The hollow-core fiber market is currently still in the trial and pilot stage, with an average annual growth rate of more than 80% from 2026 to 2030 and global demand reaching 800,000 fiber-km in 2030. Of total multi-core fiber demand, data center interconnects are estimated to account for 62% in 2030.

Challenges and opportunities coexist as a unified standards system remains to be built

While acknowledging the rapid development of new fiber technologies, Ao Li also noted that industrial progress and deployment still face multiple challenges.

Take hollow-core fiber as an example. The technology still faces five major engineering challenges: the drawable length of a single preform is less than 100 kilometers, while structural stability, loss flatness and yield need improvement, and manufacturing process maturity is low; moisture ingress and temperature sensitivity leave environmental adaptability insufficient, and service life cannot yet be assessed; the supporting device ecosystem, including high-power broadband amplifiers and connectors, is incomplete; there is a lack of a full-link testing and evaluation standards system for fiber characteristics, and evaluation methods for some key indicators have not yet been standardized; and field splicing takes a long time with relatively high loss, while construction and maintenance specifications have not yet been established.

Standardization is the key threshold for new fiber to move from "can be made" to "can be used and is trusted for use." Ao Li stressed that, overall, the international and domestic standards systems for new fiber still need to be built.

For multicore fiber, ITU-T SG15 began work in March 2025 on the G.smmcf and G.csmcf standards, launching a study of "single-mode weakly coupled multicore" characteristics based on single-core G.652/G.654, with publication expected in 2028. On the industry side, Corning, Sumitomo Electric, Fujikura and TeraHop formed the four-core space-division multiplexing multicore fiber multi-source agreement (SDM4 MCF MSA) alliance in March 2026 to develop a 4-core fiber specification for AI data centers. In China, TC6 of the China Communications Standards Association (CCSA) has completed three space-division multiplexing research projects covering fiber characteristics, optical components and transmission systems, and has approved one research project on multicore submarine cable.

For hollow-core fiber, ITU-T SG15 jointly launched a study report, "Hollow-core fibre technologies and systems," in July 2026. The report's scope covers key characteristics, application scenarios, system requirements, interoperability, deployment and maintenance. In China, CCSA has approved one industry standard, "Test methods for transmission characteristics of hollow-core fiber for telecommunications," and has launched six related projects covering optical fiber, optical components and ultra-high-speed optical transmission systems.

In closing his presentation, Ao Li stressed that future networks will not be a one-fiber show. Instead, new fiber types such as multicore and hollow-core fiber will be deployed as needed alongside conventional fiber in a heterogeneous converged architecture: enhanced multimode fiber will support short-reach, ultra-high-speed interconnects, high-density fiber will build computing-power interconnect channels, and multicore and hollow-core fiber will accelerate adoption in their respective high-value scenarios. Together, they will meet the differentiated needs of new services such as intelligent computing interconnection, 5G-A/6G and computing-power interconnection, as well as traditional services, creating a heterogeneous network that integrates multiple fiber types.