Information Transmission Media

There are the following types of cables:

· Coaxial

· Twisted-Pair

Unshielded Twisted-Pair (UTP)

Shielded Twisted-Pair (STP)

· Fiber-Optic

1. Coaxial cable is the kind of copper cable used by cable TV companies between the community antenna and user homes and businesses. It is also widely installed for use in business and corporation Ethernet and other types of local area network. Coaxial cable is called "coaxial" because it includes one physical channel that carries the signal surrounded by another concentric physical channel, both running along the same axis. The outer channel serves as a ground. There are two types of coaxial cables: thinnet (thin-wire Ethernet) and thicknet (standard Ethernet).

Thinnet is a flexible coaxial cable about 0.25-inch thick. It is used for short distance communication. Thinnet coaxial cable can carry a signal up to approximately 185 meters (or about 607 feet) before needing a repeater.

Thicknet is about 0.5-inch in diameter. Typically, thicknet is used as a backbone to connect several smaller thinnet based networks. Thicknet can carry a signal for 500 meters (about 1,640 feet) before needing a repeater.

2. Twisted pair is the ordinary copper wire that connects home and many business computers to the telephone company. To reduce crosstalk or electromagnetic induction between pairs of wires, two insulated copper wires are twisted around each other. For some business locations, twisted pair is enclosed in a shield that functions as a ground. This is known as shielded twisted pair (STP). Ordinary wire to the home is unshielded twisted pair (UTP).

3. Optical fiber (or "fiber optic") refers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic wire or fiber. Optical fiber carries much more information than copper wire and is in general not subject to electromagnetic interference and the need to retransmit signals. Single mode fiber is used for longer distances; multimode fiber is used for shorter distances.

Дата добавления: 2014-12-27