Three Classes of Cable
While there are dozens of cable types currently in use for data and telecom network cabling, they all fall within three classes, differentiated by the transmission media (i.e. what material carries electrical signals), and by how the transmission medium is shaped.
These three common classes are:
- Coaxial cable (often referred to simply as “coax”), which uses copper as a transmission medium
- Twisted-pair cable, which also uses copper as a transmission medium, but has a different structure
- Optic cable, which uses optic fibre to carry signals in the form of light
The material and build determine how much the cable costs, how it’s installed and verified, and many other operational parameters – but it also dictates how it behaves. In particular, it determines:
- The bandwidth and latency of your network – that is, how much information can be transmitted in a unit of time (megabits or gigabits per second), and how much time it takes for one unit of information to travel over the cable.
- The distance over which signals of a particular speed can be carried. Electrical signals are inherently attenuated or dampened – and the material used for the cable determines how much a signal attenuates over a given length. As they travel through the cable, data signals are also mixed with interference that cables pick from outside sources and from the electrical installation itself. After a certain point, this interference or noise “drowns out” the useful signal – and the cable material and build determine how long a signal can travel through the wire before so much interference is picked up, that the original signal can no longer be reconstructed
- Installation requirements: depending on the material and build of the cable, various types of connectors need to be used, installing the cable may require specific precautions (such as protecting cable from the elements) or special operations, such as fusion splicing.
There are several types of cable within each class, and modern company networks routinely use cables from all three classes.
The most familiar one is twisted-pair cable, which is used on virtually all office floors. Fibre cable is used primarily for long-distance cabling, such as telecom and outdoor security equipment, and high-bandwidth applications, such as data centre cabling. Coaxial cabling, while rarely used for computer data networking anymore, is still used for CATV and some radio applications.