Types of Network Cables: Twisted Pair, Coaxial, Fiber Optic

Twisted Pair Cable

Twisted pair cable consists of two conductors, usually copper, each with its own plastic insulation, twisted together. One of the cables carries signals to the receiver, and the other is used as a signal ground reference.

In addition to the signal sent by the sender, interference and noise can affect both cables and create unwanted signals. If the cables are parallel, the effect of these unwanted signals is not the same in both due to their different positions relative to noise and interference sources. This creates a difference at the receiver. Twisting maintains balance and helps to equalize the noise between the two wires.

Types of Copper Twisted Pair

  • UTP (Unshielded Twisted Pair): The most common type used in communications.
  • Screened UTP: A shielded twisted pair cable with a coating that surrounds each pair of insulated conductors. It offers better quality but is more expensive.
  • STP (Shielded Twisted Pair): Created by IBM, this cable has a woven mesh lining that surrounds each pair of insulated conductors. It improves quality by preventing noise penetration but is bulkier and more expensive.

Categories of Twisted Pair Cable

Categories are determined by cable quality, with 1 being the lowest and 7 the highest.

  • Category 1: Basic cable used in telephone systems.
  • Category 2: Unshielded twisted pair, originally used in T-type lines.
  • Category 3: Improved CAT 2, used in LANs.
  • Category 4: Improved CAT 3, used in Token Ring networks.
  • Category 5: 24 AWG cable with an envelope and a shield.
  • Category 5E: An extension of Category 5 with extra features to minimize noise and electromagnetic interference.
  • Category 6: A newer category that requires specific components from the same manufacturer.
  • Category 7 (SSTP – Screened Shielded Twisted Pair): Shielding reduces interference and increases data speed.

Coaxial Cable

Coaxial cable consists of a center conductor and a shield. Coaxial cables can carry higher frequency signals than twisted pair cables. They are classified according to Radio Government (RG) ratings. Common types include RG-29 (cable TV), RG-58 (Thin Ethernet), and RG-11 (Thick Ethernet). Popular connectors include BNC, BNC-T, and BNC terminators. They are used in cable TV and traditional Ethernet networks.

Fiber Optic Cable

Fiber optic cables have an inner core of glass or plastic surrounded by a cladding, all enclosed within an outer sheath. They transmit data signals as light. The signal propagates through the inner core by reflection. Fiber optic transmissions are increasingly popular due to their noise resistance, low attenuation, and high bandwidth. Disadvantages include unidirectional light propagation and cost. They are used in backbone networks, cable TV networks, and fast Ethernet networks.