NETWORK TRANSMISSION MEDIA: Part2

Coaxial Cables

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 following figure shows the structure of a coaxial cable.

In the preceding figure, 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.

Coaxial cables provide effective protection against EMI during data transmission. This high level of resistance to EMI is attributed to the structure of the coaxial cable, which consists of a conductor made up of thick copper or stranded wire, which is covered with an insulator coating. An outer conductor made up of a braided metal shield covers this insulator coating.
The following are the most commonly used categories of coaxial cable:
RG-6
RG-8
RG-11
RG-58
RG-59


Coaxial cables are easy to install as compared to twisted pair cables, support higher transmission rates (10 Mbps and above). In addition, because coaxial cables suffer from lower attenuation rates than TP-based cables, coaxial cables effectively ranges up to 1 Km, which is a much higher range than either of the TP cables. Another advantage of coaxial cables is that although they use copper-based wire, they are less sensitive to EMI and other electrical interferences.

The main limitation of coaxial cables is that they are more expensive than TP cables. In addition, because of the hard covering of coaxial cables, the reconfiguration and reinstallation of the current network setup becomes difficult.

Fiber Optic Cables

Fiber optic cables are based on the fiber optic technology, which uses light rays or laser rays instead of electricity to transmit data. This makes fiber optic 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 the light-conducting fiber, cladding, and insulator jacket. The cladding covers the core fiber and prevents the light from being reflected through the fiber and the insulating jacket. The outer covering (or the insulator jacket) is responsible for providing the required strength and support to the core fiber as well as for protecting the core fiber from breakage or high temperatures.
The following figure shows a cross-section of a fiber optic cable.

Fiber Optic Cable

Fiber optic cables can be differentiated into the following two categories:


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

Single Mode Cables

Multimode cables: These cables use multimode fiber, which provides multiple paths for light rays to pass through the cable. The following figure shows a multimode fiber:

Multimode Cable

Because 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. In addition, optical cables can support high bandwidths, from 100 Mbps to 2 Gbps. As a result, a network setup using fiber optic cabling can expand up to 10 Kms, without any problems. These facts have made fiber optic cabling popular on the networking market today.
Fiber optic cabling also has a few limitations. It is the most expensive cabling type. It is also cumbersome to install fiber optic networks because fibers are damaged if they are bent sharply.

Working of the Token Ring Network

Token Ring is a network architecture developed by International Business Machines (IBM). It is also a protocol, IEEE 802.5, developed by Institute of Electrical and Electronics Engineers (IEEE), which serves as a standard for IBM Token Ring.

When a token ring network is initiated, all the nodes on the network negotiate and decide upon the node that will monitor the network to ensure that the network traffic passes smoothly.

Data on the token ring network is transmitted in the form of tokens. The tokens are passed in a unidirectional way. When the destination node receives the message, it marks the message as “Read”. The message is passed in the ring and it comes back to the sender. The sender checks the message read mark to identify that the message was read by the destination node.

On the token ring network, only the node that possesses a token can transmit data. Each node on the network is allowed to hold the token for a specified time period. If the node holding the token does not have any data to transmit, it passes the token to the next node on the ring.


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