An RFS Guide to Hollow Core Fiber
HCF is a major advancement in optical fiber, with YOFC and Microsoft leading the way in pushing the boundaries of this technology. Unlike traditional solid-core fibers, and as the name suggests, it has a unique hollow core design to enable faster and more reliable data transmission with even lower latency.
In this article, we delve into why HCF is a game-changer and the applications driving its development. We examine the technology itself, its performance in real-world terms, and explore the potential we at RFS see in this new type of fiber.
A Need for Speed (…and capacity and low-latency)
Although traditional fiber technologies represent the best option for many applications needing high capacity, high-speed, low-latency connectivity, there are some use cases where the physics of what is possible needs to be pushed on all three metrics.
Artificial Intelligence (AI) is already transformational and is set to be more disruptive than the Industrial Revolution. Generative AI is now used by 71% of businesses for at least one application, with the scale of how companies utilize the technology set to grow even further and faster. Healthcare, entertainment, education, manufacturing, aerospace – virtually every sector is seeing AI as a catalyst for advancement, and with this demand comes a need for the underlying infrastructure to push AI to its seemingly limitless potential.
As AI and other data-hungry applications –like cloud computing, and edge technologies–expand, data centers become even more critical as the beating heart of our digital ecosystem. Processing and storing vast amounts of data, the demand for faster, more reliable transmission is growing unrelentingly, with no sign of slowing.
These are just two applications where HCF is set to shine. It’s designed to handle immense workloads with previously unattainable efficiency, bridging the gap between traditional fiber limitations and the rapidly increasing demands of a data-driven world.
We’ve made some bold statements on what HCF is capable of, so let’s delve into how the technology works and how it delivers on its promises.
HCF in 30 seconds
Hollow Core Fiber (HCF) is an advanced optical fiber technology designed to meet the growing demand for efficient, high-speed data transmission. Its unique hollow core structure allows light to travel through air instead of glass, significantly reducing signal loss and improving overall transmission efficiency for high-speed, low-latency communication.
HCF: Deep Dive
HCF takes a transformative approach to optical fiber technology, improving performance in four key categories.
- Ultra-Low Attenuation: Exceptional light transmission efficiency with minimal loss.
- Low Latency: Ensures ultra-fast data transmission
- Low Nonlinear Effects: Minimizes signal distortion even at high power levels.
- Low Dispersion: Maintains signal integrity over long distances.
The Technology
HCF employs a revolutionary approach to how light is transmitted to improve the performance of the fiber technology.
Whereas traditional solid-core fibers rely on total internal reflection within glass structures, HCF's hollow core design allows light to travel through air. This significantly minimizes signal loss as air has much lower attenuation compared to glass. Additionally, this enables its ultra-low dispersion capabilities, allowing HCF deployments to maintain integrity over long distances.
To address the need to reduce nonlinear distortions and ensure signal clarity, instead of relying on conventional refractive index contrasts HCF uses advanced waveguide mechanisms. This design allows HCF to maximize performance, even under high-power conditions.
While moving the needle in all the above categories, it maintains ultra-low latency to meet the complete needs of the most data-intensive applications.
Testing Data
The theory of how the technology pushes the boundaries of what we can physically achieve with fiber is a useful starting point. But it is arguably more important to demonstrate its impact with real testing data. Through RFS’s relationship with HCF leader YOFC, we are able to show comparative data to highlight the performance improvement possible using HCF.
| Solid Core Fiber | Hollow Core Fiber | Improvement | |
|---|---|---|---|
| Lower Attenuation | ≈ 0.14dB/km | <0.1dB/km | ~ 50% |
| Lower Latency | 4.911 microseconds/km | 3.356 microseconds/km | ~ 31% |
| Reduced Nonlinear Effects | ~ 2.6 x 10 -20m2/W | ~ 1.1 x 10 -23m2/W | ~ 1000 times |
| Lower Dispersion | ~ 17 picoseconds/nm/km | 2~3 picoseconds/nm/km | ~ 8 times |
Beyond the test data highlighted in the table, At the OFC (Optical Fiber Communication Conference) held in the United States in April 2025, YOFC set a new global record for the lowest attenuation at 0.05 dB/km with its latest generation of HCF.
The difference we see on every metric is significant. HCF is not an incremental step up in terms of what we can achieve with fiber. It is a complete game-changer.
HCF in the Real World
As mentioned at the start of this article, Microsoft and YOFC are the leading pioneers in the hollow-core fiber space. They have both made significant investments and committed substantial R&D to advancing the technology from decades of academic and theoretical research into a commercial proposition. Microsoft’s CEO has announced that over the next two years, 15,000 kilometers of HCF will be installed across its AI data centers, while YOFC has already seen success in facilitating China’s first HCF pilot project on a live network and has begun to service commercial orders in China and beyond.
What the Future Holds
The future of HCF extends far beyond its current use cases. Here are just a few examples of where the technology has huge potential:
Financial Trading
Financial data centers are expected to be transformed by the capabilities HCF offers, that are ideal for high-frequency trading environments. By minimizing delays in data transmission with ultra-low latency over long distances, financial institutions can gain a competitive edge in a sector where time is very literally money.
Extended Relay Station Spacing
There is also huge potential in industries, for example, telecommunication and broadcasting, that need relay sites as part of their infrastructure. HCF's superior low-nonlinearity and reduced optical distortions allow it to maintain signal integrity at higher optical power levels. This allows the distance between relay stations to be extended significantly – doubled or even tripled – resulting in lower infrastructure construction and maintenance costs.
Interconnection Between Data Centers
As HCF achieves near-light-speed data transmission, it drastically minimizes link latency between data centers while maintaining stable performance. This has the potential to disrupt the entire data center landscape by giving unprecedented flexibility for the location of data center sites. They can be positioned further apart than ever before, without compromising speed or reliability. This opens the door for data centers to be built in areas with lower electricity costs due to the high availability of cheaper renewable energy, resulting in lower OPEX that aligns with sustainability goals.
Conclusion
This is just the beginning of what we can achieve. As fiber capabilities extend, we expect to see use cases arise in numerous industries set to benefit from faster, reliable data transmission with even lower latency over ever-increasing distances.
Through our relationship with YOFC, RFS is one of only a handful of companies able to explain HCF to our customer base where the application demands ultra-high-performance fiber. To find out more about how your project can benefit from HCF, get in touch with the team.