Transmission Mediums ( Guided / Unguided ) Part 1

Transmission Medium :

• Transmission medium is the way in which data is transmitted from one place to another .

• It provide a pathway over which the message can travel from sender tp receiver .

• Each of the message can be sent in the form of data by converting them into binary digits.

• These binary digits are then encoded into a signal that can be transmitted over the appropriate medium. 

Wired / Guided Transmission Media :

• Guided Transmission Media are the cables that are tangible or having physical existence

• Bounded transmission means having connectivity between source and destination using cables or wires . The signals having to travel through this channel i.e.physical media.

Twisted Pair Cable :

A twisted pair cable is a pair of copper wires .

Copper wires are the most common wires used for transmitting signals because of good performance at low costs .

A twisted pair consists of two conductors each with its own plastic insulation , twisted together to form a signal media .

Out of these two wires , only one carries actual signal and another is used for ground reference.

To identify every cable , these cables are color coded .

This twists between wires are helpful in reducing noise ( electo-magnetic interference ) and crosstalk.

This type of cables is used in telephone lines tp provide voice and data channels .

The two types of twisted pairs are :

Unshielded Twisted Pair ( UTP ) :

• UTP is more common.
• UTP cost less than STP and easily available due to its many use.
• Due to its low cost , UTP cabling is used extensively for Local Area Networks (LANs) and telephone connections.
• UTP cables consists of 2 or 4 pairs of twisted cables.
• Cable with 2 pair use RJ11 connector and 4 pair cable use RJ45 connector.

RJ-45 connectors is used with Ethernet cables in computer networking.

RJ-11 connectors is used in connecting telephone units.

Shielded Twisted Pair ( STP ) :

• This type of cable has a metal foilcovering which encases each pair of insulator connectors.
• Electromagnetic noise penetration is prevented by metal casing . Shielding also eliminates crosstalk.
• It is similar to UTP but has a mesh shielding that is protect itfrom EMI which allows for higher transmission rate .
• It is more expensive than coaxial and UTP.

Coaxial Cable :

• Coaxial cables are copper cables with better shielding than twisted pair cables , so that transmitted signals may travel longer distances at higher speeds.
• The shield minimizes electrical and radio frequency interference.
• Coaxial cabling is the primary type of cabling used by the cable television industry and is also widely used for computer networks such as Ethernet. 

• Coaxial cable has two wires of copper .
• The core/inner copper wire in center and is made of solid conductor . It is enclosed in an insulating sheath.
• The second/outer copper wire is wrapped around , and is used to protect from external electromagnetic interference ( Noise ).
• This all is covered by plastic cover used to protect the inner layers from physical damage such as fire or water.

Fiber Optics Cable

• A fiber Optic cable is made of high quality of thin glass or plastic and iis used to transfer digital data signals in the form of light up to distance of thousand of miles.

• Fiber optic cables are not affected by electromagnetic interference , so noise and distortion is very less.
• Fiber optic cables carry communication signals using pulses of light generated by small lasers or light emitting diodes ( LEDs ).
• The cable consists of one or more strands of glass , each only slightly thicker than a human hair . The centre of each strand is called the core , which provides the Pathway for light to travel. The core is surrounding by a layer of glass called Cladding that reflects light inwards to avoid loss of signal and allow the light to pass through bends in the cable . No light escapes the glass core because of this reflective cladding .

Advantages of Optical Fiber :

• Fiber optic cables have a much high bandwidth ( BW ) than metal cables . This means that they can carry more data 
• Smaller size and lighter weight .
• Low attenuation .
• Not affected electromagnetic interference .
• Signals carrying data can travel long distance without weakening.
• Suitable for industrial and noisy areas.

Disadvantages of Optical Fibre :

• Optical fibre cables are expensive.
• Difficult to install .
• Maintenance is expensive and difficult.