Wired Media | Guided Media | Bound Transmission Media

Ø  Bound transmission media are the cables that are tangible or have physical existence and are limited by the physical geography. 

Ø  Popular bound transmission media in use are twisted pair cable, co-axial cable and fiber optical cable.

Ø  Each of them has its own characteristics like transmission speed, effect of noise, physical appearance, cost etc. 

Ø  They will transmit the data in the form of electrical signals.

1) Twisted Pair Cable:

Ø  A twisted pair cable is made of two identical wires twisted together to form a single media.

Ø  Out of these two wires, only one carries actual signal (Conductor) and another is used for ground reference (Insulator).

Ø  The twists between wires are helpful in reducing noise and crosstalk (Bleeding of signal from one wire to another i.e.)

ØThere are two types of twisted pair cables:

·     Shielded Twisted Pair (STP) Cable

·     Unshielded Twisted Pair (UTP) Cable

Ø  STP cables come with twisted wire pair covered in metal foil-It is very thin sheet of metal with aluminium, copper. This makes it more indifferent to noise and crosstalk.

Ø  UTP has seven categories, each suitable for specific use. In computer networks, Cat-5, Cat-5e, and Cat-6 cables are mostly used. UTP cables are connected by RJ45 connectors.

ØAdvantages:

·     Simple to use

·     Easy to install and maintain

·     Cheaper

ØDisadvantages:

·     The strength of signals goes on decreasing as they travel over long distance.(High attenuation i.e. loss in signal  so need repeater to transmit signal over long distance)

·     Low bandwidth

·     Data rate ranges from 1Mbps to 10Mbps

2) Coaxial Cable

Ø  Coaxial cable has two wires of copper(Concentric conductor)

Ø  The core wire lies in the center and it is made of solid conductor. The core is enclosed in an insulating sheath.

Ø  The second wire is wrapped around over the sheath and that too in turn encased by insulator sheath. This all is covered by plastic cover.

Ø  Because of its structure, the coaxial cable is capable of carrying high frequency signals than that of twisted pair cable. The wrapped structure provides it a good shield against noise and cross talk.

Ø   Coaxial cables provide high bandwidth rates of up to 450 Mbps.

Ø  There are three categories of coaxial cables namely, RG-59 (Cable TV), RG-58 (Thin Ethernet-185 meters long), and RG-11 (Thick Ethernet-500 meters long). RG stands for Radio Government.

Ø  Cables are connected using BNC connector and BNC-T. BNC terminator is used to terminate the wire at the far ends.

ØAdvantages:

·     Much better than twisted pair cable in regards of attenuation, data rate

·     Mainly used for broadband transmission i.e. sending all channels on same cable

·     High bandwidth upto 450Mbps

ØDisadvantages:

·     Expensive than twisted pair

·     Not compatible with twisted pair cable

3) Fiber Optics

Ø  Fiber Optic works on the properties of light.

Ø  When light ray hits at critical angle it tends to refracts at 90 degree. This property has been used in fiber optic.

Ø  It works on the principle of Total Internal Reflection(TIR)

Ø  From one end of it light is emitted, it travels through it and at the other end light detector detects light stream and converts it to electric data.

Ø  The Optical core of fiber optic cable is made of high quality glass or plastic through which light travels

Ø  Cladding: Reflect light back to core.

Ø  Protective Coating (Sheath): Used to prevent cable from hostile environment.

Ø  Fiber Optic provides highest mode of speed. It comes in two modes, one is single mode fiber and second is multimode fiber.

Ø  Single mode fiber of 2km can carry a single ray of light with 100Mbps whereas multimode fiber of maximum length 100km with maximum speed 2Gbps is capable of carrying multiple beams of light.

Ø  Fiber Optic also comes in unidirectional and bidirectional capabilities.

Ø   To connect and access fiber optic special type of connectors are used. These can be Subscriber Channel (SC), Straight Tip (ST), or MT-RJ.