Hollow-core fibre tech could reshape telecom’s physical layer

Inside a high-frequency trading floor, where nanoseconds delineate gain from loss, or across the fortified corridors of a command network, data must traverse vast distances swiftly and securely. Across much of the world, single-mode silica fibre has long served as the physical backbone of high-speed networks—a marvel in its time, but one now brushing against its physical limits.

The world now has its new contender: hollow-core fibre (HCF), which guides light not through glass, but through air.

Developed by researchers at the University of Southampton and also by Microsoft, the latest evolution—nested antiresonant nodeless fibre (DNANF)—has achieved a record-low attenuation of 0.091 dB/km at 1,550 nm. This surpasses the long-standing floor of conventional silica fibres, which rarely drops below 0.14 dB/km. By minimising leakage, surface scattering, and microbending losses, this design ushers in a new class of low-loss fibres suitable for both classical and quantum communication.

Rewriting the Physics of Fibre Transmission

The DNANF structure consists of a hollow central core surrounded by a ring of thin-walled capillaries—each precisely engineered to act as an antiresonant reflector. This enables tight confinement of specific light wavelengths while maintaining structural symmetry during the fibre-drawing process.

Technically, HCF marks a notable departure from photonic bandgap fibres and earlier Kagome-style designs. Unlike those, DNANF does not require intricate lattice arrangements to confine light. Instead, it relies on carefully nested tubes that support antiresonant guidance—simplifying fabrication while enhancing performance. Crucially, it avoids many nonlinear effects common in glass fibres, such as self-phase modulation and Raman scattering, making it ideal for high-power, long-distance links.

Furthermore, the air-filled core significantly reduces the refractive index contrast with the surrounding material, resulting in lower group velocity dispersion—an advantage for high-bit-rate transmission across multiple wavelengths.

Conventional fibres use total internal reflection to contain light within a silica core. But silica, however refined, introduces dispersion, attenuation, and latency. In contrast, HCF uses air, where light travels nearly 50% faster. This translates to ~5 µs/km delay, compared to ~8.5 µs/km in solid-core fibres. In applications where low latency is sacrosanct—such as algorithmic trading, AI cluster synchronisation, and battlefield telemetry—this gain is not merely incremental; it is transformative.

Early Deployments and Strategic Potential

Real-world deployments are already underway. Microsoft has integrated HCF into its Azure metro networks, enabling ultra-low-latency data paths. China Mobile reported 114.9 Tbit/s throughput across an HCF link between Shenzhen and Hong Kong. Relativity Networks, a US-based start-up, claims that HCF can extend inter-data-centre distances from 60 to 90 km without amplification—a potential boon for energy-constrained AI infrastructure.

These early projects have validated the field-worthiness of HCF, demonstrating that its fragile internal structure can be preserved over kilometres during deployment, with no field failures reported.

HCF also presents distinct advantages for defence and secure communication networks. Its ability to transmit single-photon signals makes it a viable medium for quantum key distribution, offering future-proof encryption.

Its resilience to electromagnetic interference and reduced need for repeaters make it apt for long-range, low-visibility communication in high-threat and remote environments. The potential to deploy HCF in unrepeated subsea cables is also being explored, offering cost and reliability benefits by minimising the number of amplifiers required. Also, HCF’s compatibility with mid-infrared and visible light wavelengths could unlock future use cases in sensing, tactical LIDAR, or spectrum-flexible battlefield networks.

Yet, barriers remain. HCF is difficult to manufacture at scale, lacks industry-wide standards, and entails high cost. Efforts to address this include performing pressurisation techniques, improved stack-and-draw assembly, and reduced gas absorption during production.

Its evolution trajectory, nevertheless, mirrors that of early fibre optics—once niche, now fundamental to global connectivity. To be clear, HCF will not supplant legacy fibre networks overnight. However, in domains where latency, reach, and signal fidelity are non-negotiable, it is poised to become not just a superior alternative but an indispensable one.