Physical layer - Copper medium

Copper cabling is one of the three types of physical media used for the transmission of information over data networks. The Physical Layer of the OSI Model defines the types of cabling used, and how information is encoded on to that cable. Copper cabling comes in many forms. The most commonly used copper cable types for data networks include:

  • Unshielded Twisted Pair (UTP) - This cable type is often unofficially called Ethernet cable due to its extensive use with Ethernet. It is composed of four pairs of insulated wires, where each pair is twisted, and all four pairs are covered in a polyethylene jacket.
  • Coaxial cabling - This cable type is most commonly used for cable TV and cable modem installations, but is also commonly used as RF cables connecting transceivers to antennas. 10BASE5 (ThickNet) and 10BASE2 (ThinNet) Ethernet standards used coaxial cabling as their principle medium in the 1980s.

Other types of copper cabling include:

  • Two pair telephone grade wires - used for the last mile PSTN connections to homes and businesses. This is often used for xDSL technologies.
  • 25 pair color coded - which includes 25 twisted pairs of wires each with color coded insulation typically used for connecting multiple analog phone devices within an enterprise's premises, or within a neighborhood by the local telco.

Copper cabling used for telephony and data communications also comes in categories that denote the characteristics of the cable and the kinds of technologies they can support. These categories include:

  • Cat 3 - analog telephone cables and 10BASE-T and 100BASE-T Ethernet
  • Cat 4 - used for 16 Mbps Token Ring
  • Cat 5 - 1000BASE-T Ethernet
  • Cat 5e - 2.5GBASE-T Ethernet
  • Cat 6 - 5GBASE-T at 100 meters and 10GBASE-T at 55 meters
  • Cat 6A - 10GBASE-T at 100 meters
  • Cat 7 - Primarily used with GG45 and TERA connectors, not widely used
  • Cat 8.1 and 8.2 - 40GBASE-T Ethernet