Copper Media

The most used media for data communications is cabling (copper media); that uses copper wires to transmit data and control bits between network devices. Cabling used for data communications generally consists of a series of individual copper wires; that form circuits dedicated to specific signaling purposes. 

There are three main types of copper media used in networking:

• Unshielded Twisted-Pair (UTP)


• Shielded Twisted-Pair (STP)


• Coaxial

The above cables are used to interconnect computers on a LAN and other devices such as switches; routers, and wireless access points. Each type of connection and the associated devices has cabling requirements specified by physical layer standards.physical layer standards specify the use of different connectors for different. Physical layer standards also specify the mechanical dimensions of the connectors and the acceptable electrical properties of each type.

Unshielded Twisted-Pair Cable (UTP)

Unshielded twisted-pair (UTP) cabling is the most common networking media for voice; and data communications. UTP cable consists of four pairs of color-coded wires that have been twisted 

together and then encased in a flexible plastic sheath that protects from minor physical damage. The twisting of wires helps to minimize electromagnetic and radio-frequency interference induced from one wire to the other.

 

UTP cabling, terminated with RJ-45 connectors; is used for interconnecting network hosts with intermediate networking devices, such as switches and routers.

In the figure, you can see that the color codes identify the individual pairs and wires and help in cable termination.

Shielded Twisted-Pair Cable(STP)

Shielded twisted-pair (STP) provides better noise protection than UTP cabling. However; compared to UTP cable, STP cable is more expensive and difficult to install. Like UTP cable, STP uses an RJ-45 connector.

The extra covering in shielded twisted pair wiring protects the transmission line from electromagnetic interference leaking into or out of the cable. STP cabling often is used in Ethernet networks, especially fast data rate Ethernets.

Shielded twisted-pair (STP)  cables combine the techniques of shielding to counter EMI and RFI, and wire twisting to counter crosstalk. To put on the full advantage of the shielding; STP cables are terminated with special shielded STP data connectors. If the cable is improperly grounded; the shield may act as an antenna and pick up unwanted signals.

Coaxial Cable

Coaxial cable is called "coaxial" because of the fact that there are two conductors that share the same axis. The outer channel serves as a ground. Many of these cables or pairs of coaxial tubes can be placed in a single outer sheathing and; with repeaters, can carry information for a great distance.

As shown in the figure, coaxial cable consists of:

• A copper conductor used to transmit the electronic signals.


• A layer of flexible plastic insulation surrounding a copper conductor.


• The insulating material is surrounded in a woven copper braid or metallic foil; that acts as the second wire in the circuit and as a shield for the inner conductor. This second layer, or shield; also reduces the amount of outside electromagnetic interference.


• The entire cable is covered with a cable jacket to prevent minor physical damage.

There are different types of connectors used with coax cable.

Although UTP cable has essentially replaced the coaxial cable in modern Ethernet installations, the coaxial cable design is used in:

• There are many types of coax cable that we can use in different ways following is the table of different types of coax cable

Cable Type	Impedance	Uses
RG-6	75 Ohms	Video, TV
RG-8	50 Ohms	Radio, computer
RG-11	75 Ohms	Long runs
RG-58	50 Ohms	Radio, Computer
RG-59	75 Ohms	Video, TV

 

Types of Physical Media

A network required a physical medium to connect its nodes. The physical media is where the data actually flows. You have most likely heard about OSI reference model, which defines network hardware and services in terms of the functions they perform. The OSI reference model we already discussed in detail in Chapter 1, ("Network and their building blocks.") Transmission media work at Layer 1(physical layer) of the OSI model:The physical layer represents bits as voltages, radio frequencies; or light pulses so various standards organizations have contributed to the definition of the physical; electrical, and mechanical properties of the media available for different data communications. These characteristics guarantee; that cables and connectors will function as expected with different data link layer implementations. There are three main categories of media types that will be discussed in detail later:

Copper cable

Types of cable include unshielded twisted-pair (UTP), shielded twisted-pair (STP), and coaxial cable. Copper-based cables are inexpensive and easy to work with compared to fiber-optic cables, but as you'll learn when we get into the particulars, the main disadvantage of copper cable is that it offers a limited range that cannot handle the advanced applications.

Fiber optics

Fiber offers huge data bandwidth, protection to many types of noise and interference, and enhanced security. 

So, fiber provides clear communications and a comparatively noise-free environment. The disadvantage of fiber is that it is costly to purchase and it requires specialized equipment and techniques for installation.

Wireless

Wireless media include radio frequencies, microwave, satellite, and infrared. Deployment of wireless media is faster and less costly than the deployment of cable, mostly where there is no existing infrastructure. There are a few disadvantages associated with wireless. It supports much lower data rates than do wired media. Wireless is also greatly affected by external environments, such as the impact of weather, as a result reliability can be difficult to guarantee.

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