Types of Data Cable

Data cables are used to transmit electronic information from a source to a destination. Extensively used in computer and telecommunication systems the type of data cabling is either copper or fibre optics. These can then be divided into three main types:

  • Twisted pair. (copper)
  • Coax. (copper)
  • Optic cables. (fibre)

Used in different environments, these data cables have different characteristics that make them identifiable.

Twisted Pair

Telecommunications and computer networks use mainly twisted pair copper wiring. The twisted pair cable consists of two copper cores, each with its own plastic insulation and twisted together. One wire carries the signal and other is used as ground reference. The advantage of twisting is that both wires are equally affected by external influences. This twisting in the cables helps protect the data communications from signal degradation. However, the average length for a twisted pair wire before signal degradation is approximately 300 feet.

This cable is of two types such as.

  • UTP (unshielded twisted pair)
  • STP (shielded twisted pair)

STP cable has one extra metal shield covering the insulated twisted pair conductors. But this is absent in UTP cables. The most common UTP connector is RJ45.

The unshielded twisted pair cable is classified into seven categories based on cable quality. Performance of twisted-pair cable is measured by comparing attenuation versus frequency. Attenuation increases with frequency above 100 kHz.

Data cabling systems are categorised in terms of the data rates that they can maintain without degradation. The specifications describe the cable material as well as the types of connectors and junction blocks to be used in order to conform to a category. For ISO/IEC standards, the category refers to the cable and class refers to the connector. ISO are international standards and can be followed anywhere in the world.

The two most widely-installed categories are CAT 3 (voice) and CAT 5e, traditionally, however with new installations, category 5e for voice and one high speed to support 10GBASE-T for long term usage are becoming most common.


Coaxial (coax) cable is used in older computer networks. Coax cable carries high frequency signals than twisted-pair cables and has a central core conductor of solid wire enclosed in an insulator, which is covered by an outer conductor of metal foil. This outer conductor completes the circuit and the whole cable is protected by a plastic cover.

Though the coaxial cable has higher bandwidth, its attenuation is far higher compared to twisted-pair cables. It is widely used in digital telephone networks where a single cable can carry data up to 600 Mbps.

Coax cabling requires a special connector called a BNC connector; it is used to connect the end of the cable to a device. These cables are categorized by RG (radio government) ratings. RG-59 used for Cable TV, RG-58 for thin Ethernet and RG-11 for thick Ethernet.

Fibre Optic

Used extensively by cable and telephony companies to provide fast connections to the Internet, fibre optic cable transmits data signals in the form of light. This light channel consists of two main parts: core and cladding The cladding acts as a protective cover to core.

The difference in density of core and cladding is such that a beam of light moving through the core is reflected off the cladding, instead of being refracted into it.

Fibre optic cable is light weight, and it does not have the signal degradation problems that the other two data cables suffer. However, fibre optic cable is very fragile due to the glass parts of the cable and is more expensive.

Two modes of propagation of light are possible in optical fibre such as: multimode and single mode. Multimode fibre allows multiple beams from a light source move through the core.

There are two types of connectors for fibre optic cables. The SC connector is used for cable TV, and ST connector used for connecting cable to networking devices.

Attenuation in fibre optic cable is very low compared to other two types of cable. It provides very high bandwidth and immunity to electromagnetic interference.

Being light weight and less likely to get trapped, fibre optic cables makes it more preferable to cable installation companies. Fibre optic cable is often used in backbone networks because of its wide bandwidth and cost effectiveness.


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