This Nokia Bell Labs researcher says today’s fiber optics can also sense the world By Aron Heller | Nokia, Friday, 03 Mar 2023

Our globe is hyper-connected by an elaborate network of high-capacity fiber optic cables. These strands of fiber, each about the dimension of a human hair, make up the backbone of the Internet and allow us to transmit millions of text, audio and video communications at the speed of light.

When this network suffers an outage without warning it sets off a cascading series of costly and complicated actions to quickly restore service and repair the engineering damage.

Mikael Mazur is trying to prevent that scenario from happening.

The Nokia Bell Labs researcher’s recent field trial demonstrates how communication fibers can also act as environmental sensors that provide an early detection system for network failure.

The real-time coherent transceiver prototype deployed in Mazur’s native Sweden can detect vibrations and distortions in the fiber. It can be used for continuous sensing over a 524-km live network aerial fiber that looks to usher in an era of a more versatile and robust network.

The technology could also have potentially far-reaching implications beyond the realm of telecom, providing ecological monitoring that would be helpful in measuring climate change in terms of temperature shifts and ocean current swells, and could even detect earthquakes.

It is these findings that Mazur will present next week (March 5-9) in San Diego, California at the Optical Fiber Communication Conference, the most prestigious gathering of the optical research community.

“What I do is figure out how to extract environmental information from the real-time digital signal processing engine,” Mazur explained. “The best way to sense what is going on in the network is to use the network itself.”

In other words, Mazur is seeking to “marry” the two primary functions of fiber optics that have generally been distinct from each other: communications and sensing.

Fibers to the rescue

Fibers are incredibly good vibration sensors so by incorporating this capability into existing communication cables it offers the potential for a self-monitoring system, like the fibers that exist in bridges, buildings and other critical infrastructure. These offer what is called “distributed sensing” that can warn of pending problems from extreme weather conditions and other external factors. When the fibers stretch, it helps tell engineers to be proactive in preventing a break or to reroute data traffic to avert an outage.

Some of this technology already exists in the vast submarine cable system. But Mazur’s 524-km aerial cable deployed in harsher conditions last June between the Swedish cities of Gothenburg and Karlstad is believed to be the first one to be wrapped around high-voltage power cables suspended from outdoor poles.

“We are trying to design sensing functionality that is compatible with coherent optical transceiver architectures,” Mazur said. “This is very important because we deploy so much fiber to the grid. So, if you know ahead of time that a link is going down, you can have it go down without affecting your network.”

This dual purpose provides a potential alternative to purchasing specifically designed, yet extremely expensive, fiber-sensing devices and could offer vendors a competitive advantage at a time when improving speed performance has become increasingly more difficult.

Pushing the boundaries of science

There is a fundamental limit to the quantity of error-free information that can be transmitted over any communication channel. It’s known as The Shannon Limit – named after famed Bell Labs researcher and father of information theory Claude Shannon. In optical fibers, we’re quickly approaching that theoretical boundary.

Since boosting the speed per channel has become so challenging, Mazur says there is a need to improve fiber optics in other ways. Sensing is just one such way to make them more versatile.

“Using multiple spatial channels with a fiber could lead to both higher capacities and novel sensing approaches,” explained Mazur.

Beyond protecting the network from damage or sabotage, this new function also offers benefits beyond telecom, particularly in environmental monitoring of wind, temperature, currents and more. In earthquake-prone areas of the globe, there are typically more sophisticated seismic instruments in place. But elsewhere, in the deep oceans for example, these sensing capabilities can prove helpful in providing storm, earthquake and tsunami warnings.

“From a Nokia perspective, our first interest is to protect the network and ensure reliability and robustness,” Mazur said. “But then there is this secondary use case, which is if we could enable these things, maybe the optical telecommunications network could play an even bigger role in our society than it does today.”

From Sweden to New Jersey, via Switzerland

Mazur’s motivations in this work derive from his upbringing.

He was born in Stockholm and grew up on the west coast of Sweden, where from an early age he was drawn to engineering. He briefly considered becoming a doctor or a police officer, but it quickly became clear where he was headed.

“I’ve always enjoyed building stuff, always felt more satisfied by experimental stuff,” he said. “I’ve always been a person who wanted to understand how things work.”

He then began his academic training at Chalmers University of Technology in Gothenburg, Sweden, earning a bachelor’s degree in engineering physics, a master’s in electrical engineering and a PhD in Microtechnology and Nanoscience. But it was in Switzerland where, as an exchange student at a technical institute, he “saw the light” and found his calling in optical research.

“I went to Switzerland because I wanted to go skiing,” joked Mazur, 32, who is also an avid runner, hiker and scuba diver. “But I had to take a class in optics as part of my masters, and that’s where it clicked.”

He began presenting his work at conferences, where he got to meet several Nokia Bell Labs researchers. In 2018, he completed his Bell Labs internship and in January 2020, as a post-doc, he joined Bell Labs in New Jersey as a member of technical staff in the Advanced Photonics Research Department. Today, he develops subsystems and techniques for space division multiplexing in multi-mode optical fibers, investigates multi-mode arbitrary waveform synthesis and develops real-time signal processing techniques for optical transmission and fiber sensing systems. He’s published dozens of papers in his field and is also a member of several research communities.

“The fiber infrastructure is already critical because it enables the internet, but we are trying to see if we can make it have an even bigger role than that,” he said. “We are fortifying what exists and enabling it to do new things.”

For Mazur, the greatest satisfaction comes from experimentally overcoming practical challenges. He said it’s the same engineering bug he caught as a child that drives his passion today.

“To some degree, I like optical communications because you can’t see it. It’s fascinating that we can communicate with laser light we cannot see,” Mazur said. “I’ve built systems, I’ve built prototypes, but I still find it all mind-boggling.”