How Fiber Optics Work

When we refer to “fiber” in this guide we are talking about fiber optic Internet, which is a form of fiber-optic communications. By sending a beam of light through fiber optic glass cables, we are able to transfer information through what is a truly fascinating process.

Optical Fibers

Fiber cables are made up of many smaller optical fibers. These fibers are extremely thin, to be specific they are less than a tenth as thick as a human hair. Though they are thin, they have a lot going on. Each optical fiber has two parts:

The Core: Usually made of glass, the core is the innermost part of the fiber, where the light passes through.

The Cladding: Usually made of a thicker layer of plastic or glass, the cladding is wrapped around the core.

These two parts work together to create a phenomenon called total internal reflection. Total internal reflection is how light is able to move down the fibers, without escaping. It is when the light hits the glass at an extremely shallow angle, less than 42 degrees, and reflects back again as if reflecting against a mirror. The cladding keeps the light in the core because the glass/plastic it is made of has a different optical density or lower refractive index. Both these terms refer to how the glass bends (refraction)and therefore slows down the light.

Light is transmitted down the fiber in LED or Laser pulses that travel extremely fast. These pulses carry binary data, which is a coding system that makes up everything we see on the Internet, even the words you are reading right now. Binary code is made up of bits, which are just ones and zeroes. These bits send messages in organized eight-part patterns, called bytes. It is easy to translate the bits of binary into light pulses. One pulse means one and no pulse means zero. These pulses can travel sixty miles before they experience any degradation. To transport data across thousands of miles these pulses go through optical amplifiers that boost their signal so that no data is lost.

The Last Mile

Once the pulses reach their destination, an optical network terminal (ONT) converts the light pulses into electrical Ethernet. This is how light becomes something you can use to actually connect your devices to the Internet. This conversion happens at the end of the Last Mile, which isn’t actually a mile at all, but a term for the last stretch of fiber that connects the consumer to the backbone of the Internet.

The backbone of the Internet is what makes it possible for people across the globe to connect via the web, and most of it is made of fiber optic cables. Fiber optic Internet may seem like brand new technology, but it has actually been around since the early days of the Internet. In 1988 fiber optic cables were laid under the ocean to connect the U.S. and Europe. They were the first submarine lines to be laid, and today they have expanded to crisscross the entirety of the ocean floor.

The backbone is the core of the Internet. The instant you connect to a website, no matter the device or the destination, multiple steps are being taken to bring you there, and every one of them is connected by the backbone.

Types of Last Mile Connections

There are several types of last mile fiber connections an Internet service provider (ISP) can install, each one varying in how pure your fiber optic Internet connection actually is. Each one is referred to as “Fiber to the X” or “FTTX”, with x representing where the optical fiber connection actually ends.

FTTP/FTTH/FTTB/FTTD: Fiber to the premise, home, business or desktop are the most direct fiber lines. With them, you are getting pure fiber straight to your residence, with no copper cables involved. These are also the most expensive fiber connections for the ISPs.

FTTB: With fiber to the building, the fiber line is distributed throughout the building by copper lines. This is a popular choice for apartment buildings, hotels, schools or buildings that provide Internet to several different businesses.

FTTC/FTTN/FTTS: Fiber to the cabinet/curb, neighborhood, or street are the most common fiber connections. Fiber is delivered to a street cabinet, around 1000ft from the farthest premise, and is then dispersed by copper cables. It is the most affordable fiber optic Internet connection for ISPs because they do not have to invest in costly infrastructure to the individual premises, and it can be re-distributed if/when new residence or businesses move in.