What Is Fiber and How Does It Work?

Fiber delivers internet service over the world’s fastest telecommunications conduit: fiber-optic cabling that can carry exponentially more data while being more reliable than any other internet type. Fiber is such a powerful networking conduit that every internet service provider (ISP) uses it for the most crucial parts of their networks. The internet we know today would not be possible without fiber-optic networks.

This streamlined guide provides a breakdown of exactly how fiber achieves such fast speeds and why it’s unquestionably the best type of internet connection.

Fiber internet’s advantages come from its transmission medium (light) and its conduit: fiber-optic cables. Other telecommunications lines use copper cores to carry electrical signals, whereas fiber-optic cables use extraordinarily thin strands of glass to carry light pulses.

Digital data is encoded into these light signals by modulating (changing) the light pulses’ power or “brightness.” A level of brightness above a certain threshold can represent a one, and, likewise, a level of brightness below the same threshold can represent a zero.

Because these light pulses oscillate at such high frequencies, ISPs are able to change or modulate the level of brightness very rapidly. The speed at which a signal can be modulated determines how much data can be transmitted per second, and fiber signals can be modulated much faster than other internet types, like cable.

Why is fiber better than cable (and everything else)?

Fiber’s advantages come from its conduit (fiber-optic cables) and its transmission medium (light). A signal strand of single-mode fiber can carry up to 100Gbps of data, and fiber cables can contain many strands. For some perspective, a coaxial cable maxes out at about 1 to 2Gbps. Using light to carry data allows for high-frequency modulation and far-reaching signals, which both contribute to the faster speeds and increased reliability of fiber. We’ll break down these advantages a bit further, but first, we should dispel a few common misconceptions.

The speed of light myth

Fiber is not the fastest type of internet because it travels at the speed of light. We’ve been harnessing those speeds since the deployment of the telegraph. Furthermore, no terrestrial telecommunications signals travel at the speed of light in a vacuum, as the signals are slowed by friction against their surroundings. In terms of raw speed, cable internet signals travel considerably faster than fiber light pulses, up to 80% of the speed of light, whereas fiber light signals travel at about 66% of the speed of light.

Despite a slower literal top speed, if we had a race across the country between a fiber light pulse and a cable internet transmission, fiber would still cross the finish line first, not because of raw speed but because of the superior efficiency and propagation of fiber-optic cabling.

Fiber’s long-reaching signals

If you removed the jacket of a transmitting fiber-optic cable to view the glass strands, you wouldn’t see any flashes of light. This is because the fiber is engineered to reflect 100% of the light back into the cable; it doesn’t waste any of the signal. (Also, fiber ISPs transmit in the infrared spectrum, which we can’t see.) Keeping all the light within the fiber strand helps the signal travel further before needing a boost.

You can’t say the same for other internet types. The inherent properties of the electrical signals in coaxial cables degrade quickly by comparison. Those signals distort, absorb into their surroundings, and become mangled from outside interference, all issues that fiber largely avoids. Because of this signal loss, non-fiber ISPs need to use amplifiers and repeaters to boost, copy, and rebroadcast the signal many times before it reaches customer homes. All that extra processing takes a measurable amount of time, and the difference is big enough to show up as increased latency on an internet speed test and to annoy internet customers.

Fiber’s long-persisting, clean signals don’t need as much extra processing. This is how fiber light pulses outrun cable electrical signals, despite starting with less raw speed, and why fiber internet is snappier and more responsive than other internet types.

Faster Speeds via faster modulation

Now, let’s talk about what most people consider internet speed: throughput. Throughput is the amount of data transmitted within a certain amount of time. That’s why internet speed is usually advertised in megabits per second (Mbps) or gigabits per second (Gbps). Fiber achieves more throughput than other internet types because fiber light pulses operate at extremely high frequencies.

Regardless of internet type, internet signals transmit digital data by modulating (changing) the properties of energy waves. For example, in fiber, ISPs change the brightness of the light pulses to communicate either a one or a zero. With cable internet, ISPs change the frequency of an electric signal. A higher frequency means the energy wave, such as a fiber light pulse, is oscillating faster, which means you can change the signal more rapidly.  More modulations per second means more 1s and 0s per second, which equates to faster internet speeds.

The fiber properties we’ve discussed are already more than enough to make fiber the fastest internet on the planet, but fiber pushes things even further with multiplexing, which just means taking advantage of different physical properties of the signal, enabling multiple signals to travel in the same fiber simultaneously. Fiber’s primary multiplexing method utilizes the frequency ( i.e. color) of the light pulses, sending signals over many different wavelengths or “colors” of light over a single fiber strand.

Watch out for phony fiber

Every internet provider uses fiber-optic lines for heavy data lifting, like connections between major data centers and internet hubs. What sets a bona fide fiber internet service apart is the use of fiber-optic cables for the entire network path: from the ISP data center all the way to your door. This type of network provides fiber-to-the-premises (FTTP) internet connections.

Non-FTTP providers use other conduits, like coaxial cable, wireless 5G broadcasts, or even (gulp) phone lines, to complete the “last mile” of the network that delivers service to customer’s homes.

If all ISPs use fiber, does it matter that you have a fiber-optic cable leading right up to your door? Well, yes, it matters a lot. That last stretch of network between your home can bottleneck your connection.

Unless you get a genuine FTTP connection that runs a fiber-optic cable to your home, you don’t receive the benefits fiber has over other internet types. You don’t get the speeds, symmetrical bandwidth, or lower latency. Real fiber means a fiber optic cable makes it onto your property, so make sure you confirm you’re purchasing an FTTP internet plan when you’re shopping for fiber internet.

Ready to get real fiber internet?

As you can see, home fiber internet is the best you can get. Take a look at some of the top providers in the U.S.