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Introduction to Computer Networks - Network Media Types:
Almost anyone who has connected to the Internet through a broadband connection (like cable or DSL) has used an Ethernet cable to do it. You have connected your PC’s network interface card (NIC) to your cable modem, DSL modem, or home router with an Ethernet cable. Or May be you are using your notebook and wireless connection to your wireless modem at home or office. Actually, Data is transmitted over copper wires, fiber optic cable, radio and microwaves. The term 'media' is used to generically refer to the physical connectors, wires or devices used to plug things together.
There are four major categories of media types namely:
1. Copper
   - Unshielded Twisted Pair (3,5,5e,6,7)
   - Shielded Twisted Pair
   - Coaxial Cable (Thinnet, Thicknet)
2. Fiber Optic
   - Single-mode
   - Multi-mode
3. Infrared
4. Radio & Microwave
1. Copper:
Unshielded Twisted Pair (UTP) Cable
Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks.
Bus
Unshielded Twisted Pair (UTP)
The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated six categories of wire (additional categories are emerging).
Categories of Unshielded Twisted Pair
   Category    -     Speed     -    Use
     1      1 Mbps      Voice Only (Telephone Wire)
     2      4 Mbps      Local Talk & Telephone (Rarely used)
     3      16 Mbps      10BaseT Ethernet
     4      20 Mbps      Token Ring (Rarely used)
     5      100 Mbps (2 pair)     100BaseT Ethernet
            1000 Mbps (4 pair)     Gigabit Ethernet
     5e      1,000 Mbps      Gigabit Ethernet
     6      10,000 Mbps      Gigabit Ethernet
UTP Connector
The standard connector for unshielded twisted pair cabling is an RJ-45 connector. This is a plastic connector that looks like a large telephone-style connector. A slot allows the RJ-45 to be inserted only one way. RJ stands for Registered Jack, implying that the connector follows a standard borrowed from the telephone industry. This standard designates which wire goes with each pin inside the connector.
Bus
RJ-45 Connector
Shielded Twisted Pair (STP) Cable
Although UTP cable is the least expensive cable, it may be susceptible to radio and electrical frequency interference (it should not be too close to electric motors, fluorescent lights, etc.). If you must place cable in environments with lots of potential interference, or if you must place cable in extremely sensitive environments that may be susceptible to the electrical current in the UTP, shielded twisted pair may be the solution. Shielded cables can also help to extend the maximum distance of the cables.
Shielded twisted pair cable is available in three different configurations:
    1. Each pair of wires is individually shielded with foil.
    2. There is a foil or braid shield inside the jacket covering all wires (as a group).
    3. There is a shield around each individual pair, as well as around the entire group of wires (referred to as double shield twisted pair).
Bus
Shielded Twisted Pair

Coaxial Cable

Coaxial cable uses a single conductor in the middle of a cable. The central conductor is surrounded by an insulator called the dielectric. A conductive shield is put around the dielectric. This shield acts as the second conductor for the circuit as well serves to protect the inner conductor from interference. Coaxial cable for local area network (LAN) connections is obsolete. Coaxial cable is being used in some cases for delivering the last mile of service. For e.g., coaxial cables are being used by Cable TV networks to deliver high-speed service customer premises.
Bus
Coaxial Cable
Although coaxial cabling is difficult to install, it is highly resistant to signal interference. In addition, it can support greater cable lengths between network devices than twisted pair cable. The two types of coaxial
Thin coaxial cable is also referred to as thinnet. 10Base2 refers to the specifications for thin coaxial cable carrying Ethernet signals. The 2 refers to the approximate maximum segment length being 200 meters. In actual fact the maximum segment length is 185 meters.

Thick coaxial cable is also referred to as thicknet. 10Base5 refers to the specifications for thick coaxial cable carrying Ethernet signals. The 5 refers to the maximum segment length being 500 meters. Thick coaxial cable has an extra protective plastic cover that helps keep moisture away from the center conductor. This makes thick coaxial a great choice when running longer lengths in a linear bus network.
Coaxial Cable Connector
The most common type of connector used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector (See fig. 4). Different types of adapters are available for BNC connectors, including a T-connector, barrel connector, and terminator. Connectors on the cable are the weakest points in any network. To help avoid problems with your network, always use the BNC connectors that crimp, rather
Bus
BNC Connector


2. Fiber Optic Cable

Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The center core of fiber cables is made from glass or plastic fibers. A plastic coating then cushions the fiber center, and kevlar fibers help to strengthen the cables and prevent breakage. The outer insulating jacket made of teflon or PVC.
Bus
Fiber Optic Cable
There are two common types of fiber cables -- single mode and multimode. Multimode cable has a larger diameter; however, both cables provide high bandwidth at high speeds. Single mode can provide more distance, but it is more expensive. Single Mode Fiber Optic Cable Single mode fiber is used outdoors and for long distances. Single mode fiber optic cable can operate over much longer distances. Because the fiber only allows one mode of light to propagate, light pulses put on the fiber keep their shape much longer. This allows the light pulses to travel much further without interfering with other pulses. Single mode fiber is recommended for cable runs in excess of 1.6 mi. Multi Mode Fiber Optic Cable Fiber optic cable is sometimes called wave guide or light guide because it guides the light waves along the length of the cable. Multi mode fiber is used for short cable runs, usually 1.6 mi (approximately 2 km) or less.
Ethernet Cable Summary:

      Specification           Cable Type
10BaseT           Unshielded Twisted Pair
10Base2           Thin Coaxial
10Base5           Thick Coaxial
100BaseT           Unshielded Twisted Pair
100BaseFX           Fiber Optic
100BaseBX           Single mode Fiber
100BaseSX           Multimode Fiber
1000BaseT           Unshielded Twisted Pair
1000BaseFX           Fiber Optic
1000BaseBX           Single mode Fiber
1000BaseSX           Multimode Fiber


3. Infra-Red

There are many systems today using infra-red communications. This is usually a directional infrared light signal transmitted into the air and received by nearby devices. Such systems came into use in the early 90's for use with laptops, printers and later in the 90's with cameras and handhelds.


4. Radio and Microwave

These are the signals we think of as being radio, television and satellite, but they are now being put to use in wireless Ethernet and Bluetooth communications technologies.
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Highlights
Computer Networks Media Types
Computer Networks Cables
Copper
Unshielded Twisted Pair (UTP)
Shielded Twisted Pair (STP)
Coaxial Cable
Thinnet Coaxial Cable
Thicknet Coaxial Cable
Fiber Optic
Single-mode
Multi-mode
Infrared
Radio & Microwave
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