Analog vs Digital signals

Analog Signal:-
An analog signal is a continuous wave denoted by a sine wave (pictured below) and may vary in signal strength (amplitude) or frequency (time). The sine wave's amplitude value can be seen as the higher and lower points of the wave, while the frequency (time) value is measured in the sine wave's physical length from left to right.

There are many examples of analog signals around us. The sound from a human voice is analog, because sound waves are continuous, as is our own vision, because we see various shapes and colors in a continuous manner due to light waves. Even a typical kitchen clock having its hands moving continuously can be represented as an analog signal.
                                                           

Digital Signal:-
A digital signal - a must for computer processing - is described as using binary (0s and 1s), and therefore, cannot take on any fractional values. As illustrated in the graphic below, digital signals retain a uniform structure, providing a constant and consistent signal. Because of the inherent reliability of the digital signal, technology using it is rapidly replacing a large percentage of analog applications and devices. For example, the wristwatch, showing the time of day, with its minute, hour, and sweeping second hands, is being replaced by the digital watch, which offers the time of day and other information using a numerical display. A typical digital signal is represented by 1s and 0s .
                                                         

        

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GUIDED MEDIA or WIRED MEDIA

GUIDED MEDIA or WIRED MEDIA :-
-Electrical/Optical signals are passed through a solid medium (different types of cables/wires)
-As the path traversed by the signals is guided by the size, shape and length of the wire, this type of media is called guided media.
-Also, in guided media, the signals are confined within the wire and do not propogate outside of the wire/media.
-E.g., Copper Unshielded Twisted Pair (UTP), Copper Shielded Twisted Pair (STP), Copper Co-axial cables, Fiber Optic Cables.


Twisted Pair Copper:
-It is the most widely deployed media type across the world, as the last mile telephone link connecting  every home with the local telephone exchange is made of twisted pair copper. These telephone lines are reused as last mile DSL access links to access the internet from home.
-They are also used in Ethernet LAN cables within homes and offices.
They support  low to High Data Rates (in order of Giga bits)
However, they are effective only upto a maximum distance of a few kilometres/miles, as the signal strength is lost significantly beyond this distance.
-They come in two variants, namely UTP (unshielded twisted pair) and STP (shielded twisted pair). Within each variant, there are multiple sub-variants, based on the thickness of the material (like UTP-3, UTP-5, UTP-7 etc.)
-E.g. DSL, 10/100/1000Mbps Ethernet cables


Copper Co-axial Cables
-Co-axial copper cables have an inner copper conductor and an outer copper shield, separated by a di-electric insulating material, to prevent signal losses.
-It is primarily used in cable TV networks and as trunk lines between telecommunication equipments.
-It serves as an internet access line from the home.
 -It supports medium to High Data Rates
 -It has much better immunity to noise and hence signal strength is retained for longer distances than in copper twisted pair media.


Fiber Optic Cables
-Here, information is transmitted by propogation of optical signals (light) through fiber optic cables and not through electrical/electromagnetic signals. Due to this, fiber optics communication supports longer distances as there is no electrical interference.
-As the name indicates, fiber optic cables are made of very thin strands of glass (silica).
-As they support very high data rates, fiber optic lines are used as WAN backbone and trunk lines between data exchange equipments.
-They are also used for accessing internet from home through FTTH (Fiber-To-The-Home) lines.
-Additionally, they are used even for LAN environment with different LAN technologies like Fast Ethernet, Gigabit Ethernet etc. using optical links at the physical layer.
 - OC-48, OC-192, FTTC, HFC are examples of Fiber Optical links.


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