Illuminating the Digital Age

We live in a world where streaming movies, making video calls, and conducting online banking transactions have become routine. Yet few people stop to consider the invisible network that enables it all: the vast web of fiber-optic cables spanning cities, continents, and ocean floors.

Unlike traditional copper wires, these bundles of hair-thin glass strands transmit information using pulses of light, delivering the bandwidth needed for today's high-speed internet. Though largely unseen by the average user, fiber-optic infrastructure is critical to modern life.

Govind Agrawal, the Dr. James C. Wyant Professor of Optics at the University of Rochester, has spent decades researching and teaching about this technology. His textbooks on fiber-optic communications and nonlinear optics have helped train generations of engineers around the world. He offers insights into how fiber optics work, how the cables are manufactured, and what the future holds for this vital technology.

How Fiber Optics Transmit Data

At the core of fiber-optic technology is a remarkably simple yet powerful idea: sending data as light pulses.

“When you watch a Netflix movie, it’s brought to you through blinking light,” explains Agrawal. The content is converted into a sequence of electrical pulses that are digitized into bits—ones and zeroes. A device called a modulator translates this electrical signal into laser light that turns on and off in rapid succession, much like Morse code.

Once the laser light enters the fiber, it remains confined within the strand thanks to the glass’s optical properties. “No matter how much you twist and turn the cable, your signal will come out the other end intact,” says Agrawal.

Unlike copper wires, which have physical limits on speed and capacity, fiber-optic cables can transmit data at light speed with far greater bandwidth. This capability makes them essential for delivering data-rich content such as 4K video. When the light pulses reach their destination, devices convert them back into electrical signals for use by computers and other equipment.

Crafting the Ultra-Thin Glass Fibers

Manufacturing fiber-optic cables begins with specially formulated glass rods that are about three feet long and less than half an inch thick. Though rigid in bulk form, these rods gain extraordinary flexibility when heated and drawn into fine strands.

“You put that glass tube in a furnace in a three-story-tall building and let it melt,” says Agrawal. “Gravity pulls it down, and the fiber becomes thinner and thinner until it’s fine enough to wind around a drum.”

The finished fiber is typically about a hundredth of an inch thick. To make it suitable for real-world use, manufacturers coat the fibers in protective layers and bundle them together as needed. Long-distance cables, such as those laid on the ocean floor, often contain 10 to 20 individual optical fibers, each providing an independent pathway for data transmission.

Linking Continents Beneath the Sea

Stretching fiber-optic cables across oceans is an enormous engineering feat. Massive spools of cable are loaded onto specialized ships that set off from opposite shores. As they travel, they lay the cable along the seafloor, meeting in the middle to complete the link.

“It takes months of preparation and a huge amount of money,” Agrawal notes. The costs can reach billions of dollars per project, meaning these undersea networks are typically owned by technology giants like Google, Meta, Microsoft, and Amazon.

The first transatlantic fiber-optic cable was laid in 1988. Today, nearly 600 undersea systems are active or under construction, forming a dense web of global connectivity. Each cable is designed to last at least 25 years, though occasional repairs can be costly and logistically challenging.

Looking Ahead: The Future of Fiber Optics

Despite remarkable advances, the future of fiber-optic technology still holds plenty of promise.

“The future looks quite bright,” says Agrawal. “Since we already have all this infrastructure, fiber optics will likely remain our main tool for communicating and transmitting data for the next 30 to 40 years. All we need to do is keep improving the capacity—either by sending more data per second or by putting more fibers everywhere.”

One promising innovation is space division multiplexing, which allows more data channels within the same fiber. Researchers are also exploring related fields such as nonlinear optics and nanophotonics to further enhance telecommunications. At the University of Rochester, teams are even experimenting with using fiber-optic lines to create a prototype quantum network connecting institutions in the city.

Fiber-optic cables may be hidden beneath our feet or the ocean floor, but they are the backbone of our connected world—and experts like Agrawal are working to ensure they continue to evolve for decades to come.