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Communication between two computers is not possible without a transmission medium. There are different types of media, which have different properties, and the selection of media depends entirely on the needs, size, and environment of the network. The most commonly used transmission medium is copper and fiber optic wires, air, and radio waves. This section deals with different types of cables used to connect computers in a network.
The most widely used network media is copper wire. Since copper is a good conductor of electricity, the digital signals generated by a computer are converted to electrical signals so that they can be sent over the network. The disadvantage of copper wire is that there is too much energy loss if the message is sent over long distances. Different types of copper wires are described as follows:
UTP (Unshielded Twisted Pair): Unshielded twisted pair cable is the most popular cable used in today's networks. It consists of various pairs of unshielded twisted copper wires. It is extensively used in telephone systems and computer networking due to its low cost, easy installation and maintenance. UTP cables provide transmission speed from 4 Mbps to 100 Mbps, depending on the type and category of the cable used. The disadvantage of this cable is that it cannot be used for networks spread over long distances, as its runs are limited to 100 meters or less. Since it is not shielded, it is more sensitive to electromagnetic interference.
STP (Shielded Twisted Pair): Shielded twisted pair cable consists of one or more pairs of twisted wires that are insulated with a metal foil to minimize electromagnetic interference. The metal shield is connected to the ground to prevent external signals from getting into and internal signals from getting out of the cable. Different types of STP cables with different characteristics are available. The maximum segment length that it provides is commonly 100 meters, although a few hundred meters is also possible. The advantage of using the STP cable is that its ability to reduce the EMI is better than the UTP cable. Its disadvantages are that it is costly and provides less speed than the UTP cable.
Coaxial Cable: Coaxial cables were the first to be used in Ethernet networks. This cable consists of an insulator that separates the braided inner conductor and the outer conductor, which is a woven copper braid. These cables are commonly used for cable TV connections at homes. They are also used by 10 Base5 and 10 Base2 Ethernet networks. Coaxial cable is of two types, namely the Thinnet and the Thicknet, depending on the thickness of the cable. Thinnet supports a maximum segment length of 185 meters, and Thicknet can send signals up to 500 meters. The cost of the cable depends on which type of cable is used. Thinnet is less costly and easier to install, whereas Thicknet is costlier and demands more efforts in installation. The transmission speed that these cables provide is between 2.5 Mbps and 10 Mbps. Coaxial cables are more resistant to EMI than the UTP cable, as they use insulators to minimize the external interference.
Fiber Optic Cable: Fiber optic cables are made up of glass and transmit data in the form of light, unlike the copper wire that uses electrical signals. A reflective coating that allows light beams to travel without outer interference covers the glass cable. The advantages of the Fiber optic cable are that signals can be sent at a much higher speed and to very long distances without the risk of outer interference. Fiber optic cables can be categorized into Single Mode Fiber (SMF) and Multi Mode Fiber (MMF).
- SMF (Single Mode Fiber) optic cable
The Single Mode Fiber optic cable supports high-speed local area networks (LAN) covering long distances and also wide area networks (WAN) that spread over different buildings or cities. It is used in 10GBase-LR Ethernet specification, which runs at the speed of 10Gbps. The SMF cable is so named because it allows only one mode of light to transmit.
- MMF (Multi Mode Fiber) optic cable
The Multi Mode Fiber optic cable is also used for high-speed networks that are spread over short distances. It is used for 10GBasse-SR Ethernet standard that supports the transmission speed of 10Gbps, Unlike the SMF cable, the MMF Cable allows the light signals to travel in more than one path. It is used extensively for short distance networking, as it is less costly than the SMF cable.
