As a part of UKTIN’s Optical-themed month, we spoke to Francesco Poletti, an academic professor at the University of Southampton, where he co-founded a start-up called Lumenisity.
Please tell us about your research/ business.
Lumenisty’s focus was on producing telecommunication cables that incorporate a novel type of optical fibre—one with an air core rather than the traditional glass core. Last year, Lumenisity was acquired by Microsoft Azure. In my current role, I bridge the gap between academia and industry, working to advance and scale up this groundbreaking technology.- There is a lot of buzz around hollow core optical fibres at the moment. Why?
Hollow core fibres have been a topic of interest for over two decades, yet during the first 15 years of this century they remained primarily a scientific curiosity, supporting high-profile experiments in selected laboratories worldwide. However, a recent innovative design, proposed and demonstrated by our team in Southampton, has marked a significant milestone. This breakthrough has allowed hollow core fibres to transition from theoretical concepts to real-world products. These novel fibres possess the potential to outperform the more conventional glass-based optical fibres. By guiding light through air rather than glass, they can substantially mitigate limitations imposed by the interaction between light and glass. For example, one can launch significantly more power before the fibre melts or before undesired effects caused by the glass nonlinearity arise; information is transmitted 30% faster, at speeds approaching the speed of light in the air; it seems potentially possible to lose less power as light/information propagates, reducing the need for optical amplification along the route; and finally, one can operate the fibres at wavelengths that are suited to the application and not imposed by the glass transparency. Where are the big opportunities for hollow core fibres? And for your research/ business?
We are witnessing a growing interest in this technology across various sectors. Microsoft Azure is particularly enthusiastic about scaling up production volumes for hollow core optical fibre cables, integrating them into their global network. The immediate benefit of this integration is a reduction in round-trip time or latency for data travelling within and between data centres. As more and more services rely on optical communication networks and on the cloud services they support, minimising latency becomes crucial for network and cloud operators. This importance is expected to escalate further as the demand grows for responsive (tactile) services with minimal delay between action and reaction. Additionally, the race to train ever-larger AI language models within increasingly powerful supercomputers adds to the urgency in reducing the interconnection latency.
Beyond the cloud and communication tech giants, interest in hollow-core fibres also extends to other industrial sectors. For instance, they find applications in civil and military inertial navigation, high-power laser beam delivery for industrial and biomedical purposes, and the burgeoning field of quantum engineering. Notably, these fibres have a distinct advantage: since light propagates mainly through air (with minimal overlap with glass), they exhibit inherent robustness against ionising radiation—a feature that traditional glass-guided fibres lack. Consequently, they are excellent candidates for supporting the development of sensors in contexts such as large particle colliders (like the new Future Circular Collider at CERN), advanced sensors in the next generation of fusion reactors, and even sensors for space missions.- What are your predictions for the year ahead?
In the upcoming year, there is a chance that hollow core fibres will achieve lower propagation loss compared to standard telecom fibres. If this milestone is reached, it could prompt other major fibre manufacturers to initiate research and development efforts aimed at producing air-guiding fibres. The global competition will drive technical advancements and solutions to practical challenges. Additionally, it will foster the growth of an ecosystem around these fibres, including the gradual development and introduction of custom transceivers, cables, splicers, and amplifiers into the market. Ultimately, this trajectory may lead to the establishment of international standards, although achieving this goal will likely take more than a year. - What is the one thing you’d like people to know about your work?
Over the past 50 years, the optical communication and sensing community has become accustomed to operating within a very narrow spectral region—specifically, the so-called C and L bands, spanning approximately 11 terahertz (THz). In this range, silica glass exhibits its lowest loss, and optical amplifiers based on erbium-doped silica glass have excelled. Lasers, detectors, integrated photonics, and various applications have all been constrained to function within this limited spectrum. Hollow core fibres hold the potential to revolutionise this landscape. They can in the future allow different applications to operate at wavelengths where the surrounding technology offers its most significant advantages. Single photon transmission for quantum communications could occur at the wavelength where ion traps or single photon sources and detectors have the highest efficiency, without the need for down-conversion into the near-infrared. Cheaper VCSEL and silicon detectors could bring energy saving to longer-distance optical communications, and potentially broader and better optical amplifiers operating at different spectral bands could finally see a low-loss optical fibre tailored to these wavelengths.
These are only some of the exciting applications that can be enabled by hollow core fibres.
I believe that the technology presents a remarkable opportunity for those who can seize the first-mover advantage in this field. Researchers, entrepreneurs, and companies that delve into this technology stand to benefit significantly. By capitalising on innovative applications, optimising performance, and creating tailored solutions, they can shape the future of telecommunications and beyond. The race is on, and those who pioneer this transformative technology are poised for exciting opportunities.
