60 years of fiber optics: How a carrier of light you can’t see underlies much of the modern world

Imagine a world without internet, email, streaming services or social media. Imagine having to write letters or call everyone on a rotary dial phone to communicate. Imagine having to drive to a store to buy anything and everything. Unthinkable, right?

You can thank fiber optics for all these conveniences and more. And while you’re at it, wish the fiber a happy 60th birthday in 2026.

As a materials scientist who has worked with fiber optics for over 30 years, I’ve seen how useful they are, and how scientists are working to improve them.

What are fiber optics?

Fiber optics are hair-thin strands of glass that confine and carry light. Information encoded on that light is how we communicate, watch movies, buy things and stay connected.

To carry information over long distances, the fiber must be extraordinarily clear. The magic behind an optical fiber’s transparency is a combination of material science and manufacturing. As the light journeys along the fiber, little by little, some scatters off the glass molecules themselves and is lost. In modern fiber optics, this loss is so small that light can travel hundreds of miles and still be seen.

Carrying information in the form of light over long distances requires the fiber to act like a mirror. This way it can bounce those bits of light around corners when the fiber is bent, as it might be when strung like electrical wire inside a building.

Optical fibers comprise an inner core surrounded by an outer layer called a cladding, both made from glass. Protective plastic layers surround these glass parts and keep the fiber remarkably strong. The core glass is made from a material that has a slightly higher refractive index than the cladding.

You can think of the refractive indexlike density. A denser material has more atoms or molecules for its size, so it takes the light longer to travel through it. The refractive index measures this slowing of light inside a material.

In such a design, light undergoes “total internal reflection,” bouncing off the core-clad interface. A remarkable feature of this phenomenon is that the glasses comprising both the core and clad are transparent, but when sandwiched together, light impinging on that interface at certain angles reflects off like a perfect mirror. So how are these special types of glass made?

A simple science

In the age of quantum technologies and AI, sometimes sophistication comes best from simplicity.

The optical fibers that wire our world are predominantly made from silicon dioxide, which also makes up beach sand. However, while chemically the same, beach sand is made up of tiny crystals of quartz that have been pulverized by geological weathering and the pounding of ocean waves. These natural origins riddle beach sand with impurities that can absorb light.

Manufacturers create fiber optic silicon dioxide, called silica, by chemically reacting gases that contain silicon with oxygen, leading to an ultrapure glass. This is all done using a process called chemical vapor deposition, where the reacted gases create layers of glass that build into the form of a rod. Typically, pure silica is used for the layers that make up the core and cladding, though to get a higher refractive index in the core, researchers add small amounts of other glass components to the silica. The finished rod is called a “blank” or “preform.”

That rod, containing both core and clad, is then heated and pulled into a thin fiber. Think of pulling on a wad of gum in your mouth – that thin strand is like the fiber, except scientists slowly lower the big preform into the furnace and pull out the small fiber quickly.

Another beauty of glass is that it controllably softens with temperature. This permits us scientists to reliably pull fiber from the preform rod that already has the core and clad built into it.

Billions of miles of fiber optics have been made for global communications, and it all conforms to a diameter of 125 micrometers – one millionth of a meter – with a tolerance typically less than about one micrometer.

That level of material purity and manufacturing control makes fiber optics a modern marvel. But fiber optics haven’t always been this advanced – it took time to get to this level of purity and control.

The trivergence

Three events took place within roughly a 10-year span that paved the way for today’s fiber optics.

In 1960, physicist Ted Maiman developed the laser by building on its 1950s predecessor, the maser. In 1966, 60 years ago, experiments by engineers George Hockham and Charles Kao tested the transparency of various materials along with some light-guiding structures. They determined that a glass fiber could, in theory, carry light over the span of at least a kilometer.

While that distance might not sound too good today, other communication systems at the time were losing far more signal strength.

The trick was to make the glass clean enough. With this finding, Hockham and Kao started a global race to make optical fiber that exceeded this level of transparency.

By 1970, scientists from Corning Inc. used chemical vapor deposition to make a fiber breaking Kao’s mark. With both these highly transparent fibers and more mature lasers to create light pulses, long-distance optical communication was born.

From 1970 to today, the clarity of fiber has continued to improve, becoming over 100 times clearer now and allowing networks to connect the world. For “groundbreaking achievements concerning the transmission of light in fibers for optical communication,” Charles Kao was awarded the 2009 Nobel Prize in physics.

Through the looking glass

Glass lets a lot of visible light through – you can tell by looking out your window. But interestingly, it is even clearer at colors, called wavelengths, that are invisible to the human eye. Fiber optics used in communication networks operate at a wavelength of light of about 1.55 micrometers, between 50 and 100 times smaller than a human hair. At this infrared wavelength, the interaction of the light with the silica glass is disappearingly small.

Billions of miles of fiber optics have been made since the 1970s and installed globally for communications. But the technology’s small size and weight, coupled with its high strength, flexibility and transparency, make fiber optics useful for many other applications.

Today, fiber optics are used as sensors for geologic events, such as earthquakes, as monitors for infrastructure, including bridges, roads and buildings, and as conduits for imaging and laser treatments inside the body. Optical fibers are also used as the source of light within the fiber lasers employed worldwide for machining, manufacturing, defense and security – to name just a few.

It’s remarkable how something that hardly interacts with light can underpin most of our human interactions. Fiber optics use light you can’t see to enable things most people cannot live without.

John Ballato receives funding from numerous federal funding organizations including the National Science Foundation and US Department of Defense.