Transmission Media

Amandeep SinghComputer Science Department,PCTE

Transmission Media

Guided Media

Unguided Media

WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998

Figure 7-2

WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998

Figure 7-3

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Twisted-Pair Cable

Figure 7-4 and 7-5

WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998

Effect of Noise on Parallel LinesFigure 7-6

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Noise on Twisted-Pair LinesFigure 7-7

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Twisted-Pair Cable

Figure 7-4 and 7-5

WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998

•The bandwidth depends on the thickness of the wire and the distance traveled, but several megabits/sec can be achieved for a few kilometers in many casesCategory 3 twisted pairs consist of two insulated wires gently twisted togetherthe more advanced category 5 twisted pairs were introduced with more twists which results in less crosstalk and a better-quality signal over longer distances

Twisted-Pair Cable

Figure 7-4 and 7-5

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•A twisted pair consists of two insulated copper wires, typically about 1 mm thick.•Twisting is done because two parallel wires constitute a fine antenna.•When the wires are twisted, the waves from different twists cancel out•Twisted pairs can run several kilometers without amplification, but for longer distances, repeaters are needed•Twisted pairs can be used for transmitting either analog or digital signals•The bandwidth depends on the thickness of the wire and the distance traveled, but several megabits/sec can be achieved for a few kilometers in many casesCategory 3 twisted pairs consist of two insulated wires gently twisted togetherthe more advanced category 5 twisted pairs were introduced with more twists

Unshielded Twisted-Pair Cable

Figure 7-8

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UTP Connectors

Figure 7-9

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Shielded Twisted-Pair Cable

Figure 7-10

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Coaxial Cable

Figure 7-11 and 7-12

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A coaxial cable consists of a stiff copper wire as the core, surrounded by an insulating material. The insulator is encased by a cylindrical conductor, often as a closely-woven braided mesh. The outer conductor is covered in a protective plastic sheath.

Figure 7-11 and 7-12

WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998

Coaxial CableIt has better shielding than twisted pairs, so

it can span longer distances at higher speeds.Two kinds of coaxial cable are widely used.

One kind, 50-ohm cable, is commonly used when it is intended for digital transmission from the start.

The other kind, 75-ohm cable, is commonly used for analog transmission and cable television

Fiber Optics cable

Figure 7-20

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Refraction

Figure 7-13

WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998

Fiber Optics cable

Figure 7-20

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•An optical transmission system has three key components: the light source, the transmission medium, and the detector.

•A pulse of light indicates a 1 bit and the absence of light indicates a 0 bit.

Figure 7-16

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Multimode Step-Index

Figure 7-17

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Multimode Graded-Index

Figure 7-18

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Single Mode

Figure 7-19

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Transmission Impairments

Attenuation Means loss of energy or signals.Distortion means change in signal due to long distance travellings.Noise is interference of other sources such as

Thermal noise, Crosstalk noise Induces noise from appliances and motors which act as anttena Impulse noise comes from lightening and power lines and vehicles.