In humanity’s journey toward a digital civilization, fiber optic communication is undeniably the lifeline supporting modern society. From the vast data oceans of cloud computing to the instantaneous connections of 5G networks, and the supercomputing power of intelligent computing centers, fiber optics carry the boundless dreams and possibilities of the information age.
However, as global data traffic grows exponentially, the capacity limitations of traditional single-mode fiber are becoming increasingly apparent, with signal loss and transmission latency posing significant constraints for long-distance communication. Against this backdrop, next-generation fiber optic technologies have emerged—SDM (Space Division Multiplexing) fiber breaks through capacity limits with multidimensional parallel transmission, while hollow-core fiber redefines speed benchmarks with ultra-low loss and near-light-speed transmission characteristics.
As of March 2025, these two technologies are becoming research hotspots, heralding the dawn of a communication revolution. They represent not only a technological leap but also a bridge to the future, propelling human communication to new heights.
SDM Fiber: A Breakthrough in Multidimensional Multiplexing Capacity
SDM, or Space Division Multiplexing, is one of the pioneers of next-generation fiber optic technology. Its core principle lies in leveraging the spatial dimension to enable parallel data transmission, overcoming the single-channel limitations of traditional single-mode fiber. Specifically, SDM fiber achieves this through designs such as multi-core fiber (MCF) or few-mode fiber (FMF), allowing multiple signal streams to be carried simultaneously within a single fiber.
Multi-core fiber integrates multiple independent transmission channels within its core, while few-mode fiber utilizes the spatial distribution of different light modes for multiplexing. This technological innovation can boost the transmission capacity of a single fiber by several times, or even tens of times. For instance, in late 2024, Japan’s NTT laboratories reported a 7-core SDM fiber achieving a single-fiber capacity exceeding 1 Pb/s (petabit per second), nearly ten times that of traditional fiber.
The progress in SDM fiber development is inspiring. Laboratories have already overcome several key challenges, such as suppressing crosstalk between cores and designing efficient couplers. However, hurdles remain: the manufacturing process for multi-core fiber is complex and costly, while few-mode fiber requires solutions for intermodal interference.
Nevertheless, as photonic device integration matures, SDM fiber is steadily advancing toward practical application. In 2025, industry experts predict that the first commercial SDM fibers will be deployed in intelligent computing centers to support the massive data throughput required for artificial intelligence training. For example, an intelligent computing center equipped with SDM fiber could elevate inter-cluster communication bandwidth to the Tb/s level, significantly accelerating model iteration speeds.
Moreover, in data-intensive applications such as 8K video streaming, virtual reality, and cloud gaming, SDM fiber will shine, delivering seamless user experiences.
The significance of SDM fiber lies not only in its capacity boost but also in ushering in a multidimensional era of optical communication. It serves as an “information superhighway” with boundless capacity, laying the foundation for the future of a digital society.
Hollow-Core Fiber: Ultra-Low Loss and High-Speed Transmission
Running parallel to SDM fiber is the rise of hollow-core fiber (HCF), a technology that revolutionizes the medium of light transmission—from solid glass cores to air cores—utilizing air’s extremely low refractive index for signal propagation.
The results are astounding: loss as low as 0.1 dB/km, far below the 0.2 dB/km of traditional fiber, and transmission speeds approaching the speed of light in a vacuum (99.7%), reducing latency by about 30%. These characteristics stem from the unique structure of hollow-core fiber: a hollow core surrounded by photonic bandgap or anti-resonant reflective layers that “trap” light for transmission through air.
Research on hollow-core fiber focuses on two designs. Photonic bandgap fiber (PBF) controls light waves through periodic microstructures and has achieved ultra-low loss in labs, while anti-resonant fiber (ARF), with a simpler structure, offers similar performance with greater cost-effectiveness potential.
In 2024, the University of Southampton in the UK showcased an anti-resonant hollow-core fiber with a transmission distance of 1,000 kilometers and a loss of just 0.12 dB/km, marking a critical step toward commercialization. However, challenges persist: the high precision required for microstructures increases production difficulty, and the mechanical stability of the core needs further optimization.
The application prospects for hollow-core fiber are vast. In long-distance backbone networks, its ultra-low loss can reduce the number of relay stations, lowering construction and maintenance costs. In high-performance computing fields, such as intelligent computing centers and quantum communication networks, its low-latency properties will significantly enhance system response times.
Post-2025, with breakthroughs in manufacturing processes, hollow-core fiber is expected to see initial commercial trials in transoceanic communication and ultra-large-scale data centers. It acts as a “lightspeed channel,” pushing global network connectivity efficiency to its limits.
Technology Comparison and Synergistic Development
While both SDM fiber and hollow-core fiber are next-generation technologies, they each have distinct focuses and complement each other. SDM fiber emphasizes capacity expansion, making it ideal for short-distance, high-throughput scenarios like data center interconnects, whereas hollow-core fiber prioritizes loss and latency optimization, suiting long-distance backbone transmission.
Their technical strengths create synergy: SDM’s multi-channel design can integrate with hollow-core fiber’s low-loss properties to create a “super fiber” combining high capacity and low latency. For example, a multi-core hollow-core fiber could handle Pb/s-level data while maintaining signal integrity over thousands of kilometers.
Currently, the industry ecosystem reflects both competition and collaboration. SDM fiber, being relatively mature, has attracted heavy investment from communication equipment giants like Huawei and Nokia, while hollow-core fiber is seeing breakthroughs in academia and startups, such as the UK’s Lumenisity, which is driving its commercialization. In the future, as standardization progresses, these two technologies are likely to develop synergistically, meeting the diverse needs of next-generation communication networks.
Future Outlook and Challenges
Standing at the cusp of 2025, the commercialization of next-generation fiber optic technologies is within sight. SDM fiber is projected to achieve large-scale deployment by 2026, initially serving data centers and 5G/6G base station interconnects, while hollow-core fiber may enter the backbone network market after 2027, gradually replacing some traditional cables. The market impact will be profound: forecasts suggest that by 2030, the SDM and hollow-core fiber industries could exceed $100 billion, reshaping the global communication landscape.
However, the path to widespread adoption is not without obstacles. Standardization remains a primary challenge: interface specifications for multi-core fiber and loss testing standards for hollow-core fiber urgently need unification. Additionally, upgrading existing optical networks is costly, and compatibility with traditional fiber must be addressed. Industry collaboration will be essential to bridge the gap from lab to market.
Looking ahead, the fusion of SDM and hollow-core fiber will provide robust support for 6G networks, quantum communication, and ultra-large-scale intelligent computing. They represent not just technological innovation but milestones in communication civilization, ushering global connectivity into an era of limitless capacity and boundless speed.
SDM fiber and hollow-core fiber embody two major leaps in optical communication technology. The former breaks capacity bottlenecks with multidimensional multiplexing, while the latter redefines efficiency with ultra-low loss and high-speed transmission. As of 2025, these technologies are transitioning from the lab to reality, signaling the opening of a communication revolution.
They will not only meet the digital society’s insatiable demand for data and speed but also reshape how people connect with each other and the world. Just as fiber optics evolved from a single strand into today’s communication backbone, the future of SDM and hollow-core fiber holds infinite possibilities. How will next-generation fiber lead us toward the vast sea of stars? The answer may lie just beyond tomorrow.
