A+: Fiber Optic and Coax Cables

Fiber-optic cabling transmits signals with light rather than with electrical signals, which makes it immune to electrical interference. It is used primarily as a backbone between networks.

When Ethernet is run over fiber-optic cables, the letter F is used in place of T (twisted pair) in the name. For example, 10BASE-F is 10 Mbps Ethernet running on fiber-optic cable, 100BASE-F is 100 Mbps Ethernet running on fiber-optic cable, and so on.

Fiber-optic cable comes in two major types:

    • Single-mode— Has a thin core (between 8 and 10 microns) designed to carry a single light ray long distances.

    • Multi-mode— Has a thicker core (62.5 microns) than single-mode; carries multiple light rays for short distances.

Fiber-optic cabling can be purchased prebuilt, but if you need a custom length, it should be built and installed by experienced cable installers because of the expense and risk of damage. Some network adapters built for servers are designed to use fiber-optic cable. Otherwise, media converters are used to interconnect fiber optic to conventional cables on networks.

Coaxial cables ('Coax')

Coaxial cabling is the oldest type of network cabling; its data wires are surrounded by a wire mesh for insulation. Coaxial cables, which resemble cable TV connections, are not popular for network use today because they must be run from one station directly to another rather than to or from a hub/switch.

Coaxial cabling creates a bus topology; each end of the bus must be terminated, and if any part of the bus fails, the entire network fails.

The oldest Ethernet standard, 10BASE5, uses a very thick coaxial cable (RG-8) that is attached to a NIC through a transceiver that uses a so-called “vampire tap” to connect the transceiver to the cable. This type of coaxial cable is also referred to as Thick Ethernet or Thicknet.

Thin Ethernet, also referred to as Thinnet, Cheapernet, or 10BASE2 Ethernet was used for low-cost Ethernet networks before the advent of UTP cable. The coaxial cable used with 10BASE2 is referred to as RG-58. This type of coaxial cable connects to network cards through a T-connector that bayonet-mounts to the rear of the network card using a BNC connector. The arms of the T are used to connect two cables, each running to another computer in the network.

If the workstation is at the end of a network, a terminating resistor is connected to one arm of the T to indicate the end of the network. If a resistor is removed, the network fails; if a station on the network fails, the network fails.

Two other types of coaxial cable are common in cable Internet, satellite Internet, and fixed wireless Internet installations:

• RG-59— Used in older cable TV or satellite TV installations; 75-ohm resistance. Also used by the long-obsolete Arcnet LAN standard.

• RG-6— Uses same connectors as RG-59, but has a larger diameter with superior shielding; used in cable TV/Internet, satellite TV/Internet, and fixed wireless Internet/TV service; 75-ohm resistance.