Fiber optics are the backbone of our modern computer networks. From long-range communications over the Internet to high-speed information transfer in data centers and exchanges, optical fiber remains essential in our globalized world.
However, fiber networks are not structurally perfect and the transfer of information can be compromised if something goes wrong. To solve this problem, physicists at the University of Bath in the UK have developed a new type of fiber designed to improve the robustness of networks. This robustness could prove especially important in the age of quantum networks.
The team fabricated optical fibers (the flexible glass channels through which information is sent) that can shield light (the medium through which data is transmitted) using the mathematics of topology. Most importantly, these modified fibers are easily scalable, meaning that the structure of each fiber can be preserved for thousands of kilometres.
The Bath study is published in the latest issue of Scientists progress.
Protect the light from clutter
In its simplest form, optical fiber, which is typically 125 µm in diameter (similar to a thick hair) comprises a solid glass core surrounded by a sheath. Light travels through the core, where it bounces off as if reflecting off a mirror.
However, the path taken by an optical fiber as it traverses the landscape is rarely straight and undisturbed – twists, loops and switchbacks are the norm. Distortions in the fiber can cause information to degrade as it travels between sender and receiver. “The challenge was to build a network that takes robustness into account,” said physics doctoral student Nathan Roberts, who led the research.
“Every time a fiber optic cable is manufactured, there are inevitably small variations in the physical structure of the fiber. When deployed in a network, fiber can also twist and bend. One way to counteract these variations and defects is to ensure that the fiber design process emphasizes strength. This is where we found topology ideas useful. »
To design this new fiber, the Bath team used topology, which is the mathematical study of quantities that remain the same despite constant distortions of geometry. Its principles are already applied to many areas of physics research. By relating physical phenomena to immutable numbers, one can avoid the destructive effects of a cluttered environment.
The fiber designed by the Bath team deploys topological ideas by including several light-conducting cores in a fiber, connected to each other in a spiral. Light can jump between these nuclei but gets trapped in the edge due to the topological design. These edge states are protected against disturbances in the structure.
The bathroom physicist, Dr. Anton Souslov, co-author of the study as theory leader, said: ‘Using our fiber, the light is less affected by environmental disturbances than it would be in an equivalent system devoid of topological design.
“By adopting optical fibers with a topological design, researchers will have the tools to anticipate and prevent signal degradation effects by building intrinsically robust photonic systems. »
Theory meets practical experience
Bath physicist Dr Peter Mosley, who co-authored the study as lead investigator, said: ‘Scientists have previously applied the complex mathematics of topology to light, but here at the University of Bath we have a lot of experience in the physical production of fibres. optics, then we combine the math with our experience to create a topological fiber. »
The team, which also includes PhD student Guido Baardink and Dr Josh Nunn from the Physics Department, is now looking for industrial partners to further develop their concept.
“We are very keen to help people build strong communication networks and are ready for the next phase of this work,” said Dr. Souslov.
Mr. Roberts added, “We have demonstrated that it is possible to make miles of topological fiber wound around a coil. We envision a quantum internet where information will be robustly transmitted across continents using topological principles. »
He also pointed out that this research has implications beyond communication networks. He said, “The development of fibers is not only a technological challenge, but also an exciting scientific field in its own right.
“Understanding how to design fiber optics has led to light sources ranging from bright ‘supercontinuous’ that cover the entire visible spectrum to quantum light sources that produce single photons – single particles of light. »
The future is quantum
Quantum networks are expected to play an important technological role in the coming years. Quantum technologies have the ability to store and process information more powerfully than today’s “classic” computers, as well as send messages securely over global networks without any possibility of eavesdropping.
But quantum states of light that transmit information are easily affected by their surroundings, and finding a way to protect them is a major challenge. This work could be a step towards retaining quantum information in optical fibers using topological design.