Demystifying Ethernet and Fiber Optics

Light signals illuminating the ends of fiber optic wires

In our last article, we talked about TCP and UDP, the protocols that handle the delivery and verification of data sent over the internet. In this article we will shift our focus to hardware: how is data passed between devices?

Ethernet and Fiber Optics are probably terms you’ve heard before, maybe in advertisements or skimming through E-Bay. You may already know that they have something to do with wired communication. But what are they really, and why is Fiber Optics all the rage now? This article will help you understand!

What is Ethernet?

Ethernet is a protocol for wired communications. It is most commonly used for Local Area Networks (LAN), i.e. small networks usually controlled by switches. However, the Ethernet protocol can be used for MAN (Metropolitan Area Networks) and WAN (Wide Area Networks) as well.

First developed by Xerox in 1973, it was standardized in 1980 by the Institute of Electrical and Electronic Engineers (IEEE) and has since gone through many revisions to improve bitrate and power usage. The standard for Ethernet and other wired communication infrastructure (IEEE 802) specify both the type of wire and how data is sent through it.

An ethernet cable is a telecommunications cable that meets the IEEE specification. Any cable you use to connect an internet-facing device to a switch or router is most likely an Ethernet cable.

Old Network Cable Types

The Ethernet standard has gone through many changes to improve bitrate and power usage. Most significant of these is the type of cable used to transfer the data.

Layers of a coaxial cable (image source)

The first telecommunications cables were known as coaxial (or coax) cables. Coax cables were first used in 1858 but were first patented in 1880 by British mathematician Oliver Heaviside. They were originally used for telegraph, radio and television communications, and 1980 to the 90’s were the Ethernet standard for 10Mb/s communication. They came in two varieties: thinnet (10BASE2 standard) or thicknet (10BASE5).

Coax cables consisted of a conductive wire (usually copper) surrounded by a dielectric layer and a metallic shield, all covered in an insulating jacket. The key benefit of coaxial cables was that the electrical field was contained within the metal shield. However, this is only true for ideal, infinitely smooth coax cables. In the real world, noise and signal leakage was a problem, and the cables were already very stiff. If internet speeds were to improve, another solution was needed.

Inside a twisted pair cable (image source)

Starting in the ‘90’s, the twisted pair design became the most performant Ethernet standard. Twisted pair cables could achieve bitrates from 10Mb/s to 10Gb/s. The 10Mb/s variety was called 10BASE-T or Category 3. The 100Mb/s standards were known as 100BASE-TX, Cat5, and Cat5e. Finally, the 10Gb/s variety was called 10GBASE-T.

As the name suggests, a twisted pair cable consists of four pairs of copper wires, each twisted in a helix shape. Twisted pair cables can be shielded (STP) or unshielded (UTP). In the shielded version, each pair is given its own insulating jacket, whereas the same is not true for the unshielded version. However, the unshielded version may have a separator or drain wire to achieve the same level of protection. In general, the unshielded variety is more common for cost reasons.

The twisted pair design dramatically increased internet speeds and reduced the problem associated with coax cables. But twisted pair cables are not the most performant cable out there.

Fiber Optics

Inside a fiber optic cable (image source)

Time for the main event!

Currently, the Ethernet standards with the highest bitrates use fiber optic cables. The standards go up to 100 Gb/s, but the best fiber optic cables support bitrates on the order of terabits. Unlike the previous types of cables, fiber optics is most commonly used for intercontinental, WAN communication.

What is most interesting about these cables, though, is their design. Instead of electrical signals passing through copper wires, infrared light is passed through threads of glass or plastic. This design is well-suited for long-distance communication because the signals are immune to electromagnetic interference and they taper off less quickly.

Fiber optics is nothing new. The first optical fiber was developed in the ’70s and its use as a communication medium was investigated in the 80s and 90s. It only took off in the 2000’s when optical fiber became commercially available. Since then, fiber optic cables have become an integral part of our global telecommunications system. ISPs (Verizon, AT&T, Optimum, etc.) have also invested in providing fiber optic internet to the home.

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