Network Media

Network Media

The physical channel that connects network components, such as nodes and printers, is known as transmission medium or network medium. The transmission medium determines speed and connectivity of the network, the resulting overall performance of the network, and the investment required to set up the network. The two types of network media are:

Cables : 

Cables connect networks over short distances. Different types of cables that can be used to set up networks include twisted pair cables, coaxial cables, and fiber optic cables.

Wireless :

 Wireless transmission channel connect mobile computers, such as laptops and PDAs, over a network. Various types of wireless transmission media are radio wave and microwave media.

Based on the type of media in the network, you can form wired network or a wireless network.

Wired Network

Cables are conventional media that is used to set up wired networks. 

The following types of cables are available to set up a wired network:

• Twisted pair cable
•  Coaxial cable 
• Fiber optic cable
•  Twisted Pair Cable 

Twisted pair cables

 are the most widely used cables for setting up networks. A twisted pair cable uses copper wires, which are good conductors of electricity. However, when two copper wires are placed in close proximity, they interfere with each other’s transmission, resulting in EMI. This is known as crosstalk. In a twisted pair network cable, multiple pairs of wires are twisted around each other at regular intervals. The twists negate the electro- magnetic field and reduce network crosstalk . Twisted pair cables are easy to set up, economical, and widely available media for network transmission. However, this media cannot be used in areas where network security is critical or the network is close to electronically sensitive equipment that may prove to be a potential source of EMI. Twisted pair cables are of the following types:

1. Unshielded Twisted Pair (UTP) cables
2.  Shielded Twisted Pair (STP) cables

 Unshielded Twisted Pair Cables 

UTP cables are the most commonly used cabling media. This type of cable is generally used in telephone systems. UTP cables consist of a set of twisted pairs that are covered with a plastic jacket. However, this plastic jacket does not provide any protection against EMI. To ensure that data transmission is not disrupted due to EMI, UTPs are not installed in close proximity to electro-magnetic devices. Another problem related to these cables is the signals that the UTP cables carry undergo rapid attenuation. As a result, the recommended length of these cables is not more than 100 meters. 

Shielded Twisted Pair Cables 

STP cables consist of multiple twisted pairs surrounded by an insulator shield. This shield protects the copper-based core from EMI. This insulator shield, in turn, is covered with a plastic encasement.

STP cables are protected against EMI by two layers. As a result, they are less sensitive to EMI and interference. However, STP cable shielding should be grounded to prevent interference in the cable. In addition, as compared to UTP, STP cables offer higher transmission rates - from 16 Mbps to 155 Mbps. Despite high transmission rates, STP cables have a number of limitations. They are expensive and not as widely available as UTP and coaxial cables. STP cables are not implemented commonly on large networks because of their incompatibility with the normal telephone cabling. 

Coaxial cables, 

commonly referred to as coax cables, derive their name from their structure. The structure is designed in a way that the two conductors share a common axis. The structure of the coaxial cable consists of a center conductor responsible for transmitting data. The outer conductor or shield protects this center conductor from EMI, ensuring that data transmission is not disrupted. The insulator provides a uniform space between the two conductors. A plastic jacket covers the cable and protects it from damage.

Fiber Optic Cable

 Fiber optic cables are based on fiber optic technology, which uses light rays or laser rays instead of electricity to transmit data. This makes fiber optics a suitable carrier of data in areas that are prone to high levels of EMI or for long distance data transmissions, where electrical signals may be significantly distorted and degraded. The components of a fiber optic cable include light- conducting fiber, cladding, and insulator jacket. The cladding covers core fiber and prevents light from being reflected through the fiber and the insulating jacket. The outer covering (or the insulator jacket) is responsible for providing required strength and support to the core fiber as well as for protecting the core fiber from breakage or high temperature. The fiber optical cables can have single or multiple paths for light rays. Based on this, fiber optic cables can be differentiated into the following categories:

Single mode cables : 

These cables use single mode fiber, which provides a single path for light rays to pass through the cables. A single mode fiber is suitable for carrying data over long distances. The following figure shows a single mode cable.

Multimode cables :

 These cables use multimode fiber, which provide multiple paths for light rays to pass through. Light rays are unaffected by large distances or environment, the signals do not attenuate or suffer from EMI or other interferences. This makes multimode cables extremely safe and prevents outsiders from eavesdropping on an ongoing transmission.