Transmission Media and its different types

According to laws of physics, communication is nearly impossible without the existence of a transmission media. Thus transmission medium has been playing an important role in the world way before our existence, from our day-to-day communication to even communicating in a computer network.

In this article we will be discussing various kinds of transmission media and how does a computer network function using these different medias. Also we will be looking at various applications of it with advantages and disadvantages. So without any further delay let's begin.

Types of Transmission Media:

1. Guided Transmission Media
2. 1. Twisted Pair Cables
   2. Co-Axial Cables
   3. Fibre-optic Cable
3. Unguided Transmission Media
4. 1. Radiowaves
   2. Microwaves
   3. Infrared waves

Speed has been the major factor while measuring a computer network's performance, and fortunately we can say that guided transmission medium have speeds greater than unguided transmission medium.

Twisted Pair Cable

This was the first of it's kind, and was used almost in every computer network in the early 1960's. Consists of 8 cables and comes down to 4 pairs of twisted cables, 2 for incoming and 2 for outgoing at least for today's generation. Earlier only 1 pair each were used for incoming and outgoing which resulted in slower speeds. The prominent reason for twisting those cables is to reduce the electromagnetic interference.

In short according to the laws of physics any medium that is carrying a signal or simply current produces a electromagnetic field around it, this makes the data corrupt meaning changes the data during transmission, hence this phenomena needs to be reduced. To do so we use a clever method of twisting the cables which makes interference very low. There is also another way of acheiving the same thing by introducing shielding. 

1. Unshielded Twisted Pair Cable: (UTP)
   As the name suggests these cables have no outer cover that prevents electromagnetic intereference. These are cheaper and are used widely among many local area networks.
2. Shielded Twisted Pair Cables: (STP)
   This cable has a outer shield that blocks the electromagnetic interference entirely due to the added twisting. These cables are very expensive and are used in high speed data server.

Further these cables are used in ethernet which is a popular networking cable standard, are basically color coded in two types, so you need to use the appropriate RJ45 connector to make these cables usable. 

1. T568a
2. T568b

Also these ethernet cables are divided in to two types according to their function as

1. Straight Ethernet Cable
   This cable connects to same kinds of colour coding at each end (eg. T568A-5T68A or T568B-5T68B).
2. Cross-over Ethernet Cable
   This cable connects two different kinds of colour coded ethernet cable, under the hood swaps the cable for Tx Transmission and Rx Receiving.

Usually nowadays MDI-X technology is integrated into the networking devices that auto-detects and configures itself to receive data frames accordingly which completely wipes the need for using straight and cross-over twisted pair Ethernet cables.

These Ethernet cables are also further classified into different CATEGORIES on the basis of speed.

1. CAT1
2. CAT2
3. CAT3
4. CAT4 16gbps
5. CAT5 1gbps
6. CAT5E - Enhanced Version 1gbps
7. CAT6 10gbps
8. CAT6A 10gbps and so on...

Pros: Cheap and Easy to install

Cons: Low data rate and short range

Co-Axial Cable

It is a copper cable with metal shielding and other engineered components to prevent electromagnetic interference. Primarily used by cable TV companies to connect satellite antennas to customer homes and businesses.

Pros: 

1. Used in high frequency applications 
2. High bandwidth and cheap
3. Reduces attenuation and shielding 
4. Reduces noise

Cons:

1. Bulky and not easy to install
2. Grounding Necessary

Optical Fibre Cable

It is a special kind of cable that is able to transmit digital data in the form light with extremely high speeds. These kind of cables use different wavelengths to channelise the whole bandwidth into different bands for Wavelength Division Multiplexing (WDM). The Small Form Factor Pluggable (SFP) device is responsible for conversion of digital data or electrical signals into light signals.

There are two kinds based on size of the wire core:

1. Single-Mode Fibre (SMF)
   Uses higher wavelengths like 1310nm and  1550nm which provide higher throughput rates. It only supports upto a range of 120km so can only be used across a city.
2. Multi-Mode Fibre (MMF)
   Uses lower wavelengths like 850nm and provides slower throughput rates and also supports a range only upto 550m which is a drastic fall comparing with the previous one.

Choice of the optical fibre is highly dependent upon the range of the network, what kind of throughput rates are desired and which Small form factor pluggable is available. Also we should note that unlike an ethernet cable we cannot upgrade it from MMF to SMF without upgrading the SFP. Also SMF is very expensive than MMF and these optic fibre cables are used in at the backbone of the internet, laid down in the oceans and data centres across the globe.

Pros: 

1. Very fast and high bandwidth 
2. Easy to install and highly flexible physically
3. Non existence of electromagnetic intereference

Cons:

1. Costly and fragile
2. Not easy to install

Congratulation my dear, you have successfully gained knowledge on different types of transmission media with their applications, advantages and disadvantages. Now you may go on further learning various topologies used for designing and implementing a network.

Thank You !

All the best and have a nice day..