Guided and unguided transmission media can be used to transmit signals. Guided media includes twisted pair, coaxial cable, and fiber optic cable, which use a physical medium to transmit signals. Unguided media transmits signals through wireless technologies like radio waves. Key factors in transmission include bandwidth, impairments like attenuation, and number of receivers. Common guided media are twisted pair, most widely used in telephone networks; coaxial cable, used for television and cable networks; and fiber optic cable, used for long-distance trunks.

1. 1
Transmission Media
lesson 3

2. 2
Overview
• Guided transmission media – wire (twisted pair,
coaxial cable, fiber)
• Unguided – wireless (radio wave, microwave,
satellite)
• Characteristics and quality determined by
medium and signal
• For guided, the medium is more important
• For unguided, the bandwidth produced by the
antenna is more important

3. 3
Design Factors
• Bandwidth
—Higher bandwidth gives higher data rate
• Transmission impairments
—Attenuation
• Interference
• Number of receivers

4. 4
Electromagnetic Spectrum

5. 5
Guided Transmission Media
• Twisted Pair
• Coaxial cable
• Optical fiber

6. 6
Twisted Pair

7. 7
Twisted Pair - Applications
• Most common medium
• Telephone network
—Between house and local exchange (subscriber loop)
• Within buildings
—To private branch exchange (PBX)
• For local area networks (LAN)
—10Mbps or 100Mbps

8. 8
Twisted Pair - Pros and Cons
• Cheap
• Easy to work with
• Low data rate
• Short range

9. 9
Twisted Pair - Transmission
Characteristics
• Analog
—Amplifiers every 5km to 6km
• Digital
—Use either analog or digital signals
—repeater every 2km or 3km
• Limited distance
• Limited bandwidth (1MHz)
• Limited data rate (100MHz)
• Susceptible to interference and noise

10. 10
STP &UTP
• STP&UTP

11. 11
Unshielded and Shielded TP
• Unshielded Twisted Pair (UTP)
—Ordinary telephone wire
—Cheapest
—Easiest to install
—Suffers from external EM interference
• Shielded Twisted Pair (STP)
—Metal braid or sheathing that reduces interference
—More expensive
—Harder to handle (thick, heavy)

12. 12
UTP categories
The Electronic Industries Association (EIA) has developed standards to grade
UTP.
1. Category 1. The basic twisted-pair cabling used in telephone systems.
This level of quality is fine for voice but inadequate for data
transmission.
2. Category 2. This category is suitable for voice and data transmission of
up to 2Mbps.
3. Category 3.This category is suitable for data transmission of up to 10
Mbps. It is now the standard cable for most telephone systems.
4. Category 4. This category is suitable for data transmission of up to 20
Mbps.
5. Category 5. This category is suitable for data transmission of up to 100
Mbps.

13. 13
Coaxial Cable
Coaxial cable consist the followings layers in its construction
-The copper conductor
-Insulation layer of plastic foam
-Second conductor or shield of wire mesh tube or metallic foil
-Outer jacket of tough plastic
Coaxial cable can be used over longer distances and support more
stations on a shared line than twisted pair

14. 14
Coaxial Cable Applications
• Most versatile medium
• Television distribution
—Ariel to TV
—Cable TV
• Long distance telephone transmission
—Can carry 10,000 voice calls simultaneously
—Being replaced by fiber optic
• Short distance computer systems links
• Local area networks

15. 15
Coaxial Cable - Transmission
Characteristics
• Analog
—Amplifiers every few km
—Closer if higher frequency
—Up to 500MHz
• Digital
—Repeater every 1km
—Closer for higher data rates

16. Coaxial cable
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17. • Coaxial types:
— Thicker used with large networks.
— Thinner used with small networks.
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Coaxial Cable (or Coax)

18. Coax Advantages & Disadvantages
Advantages Disadvantages
• Higher bandwidth
—400 to 600Mhz
• Much less susceptible to
interference than twisted pair
• It will not cause a toxic gas
when its burned. That’s why
they use it in some buildings.
• High attenuation rate makes
it expensive over long
distance
• It’s not used anymore due to
high cost and other technical
factors.
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19. 19
Optical Fiber

20. 20
Optical Fiber - Applications
• Long-haul trunks
• Metropolitan trunks
• Subscriber loops
• LANs

21. 21
Optical Fiber - Transmission
Characteristics
• Act as wave guide for 1014 to 1015 Hz
—Portions of infrared and visible spectrum
• Light Emitting Diode (LED)
—Cheaper
—Wider operating temp range
—Last longer
• Injection Laser Diode (ILD)
—More efficient
—Greater data rate

22. Digital data is converted to light
• Single mode - one light source flashes a light down the
cable.
—can carries single ray of light
• Multimode - supports many simultaneous light
transmissions.
—capable of carrying multiple beams of light.
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Fiber Optic Types

23. Fiber Optic Advantages & Disadvantages
Advantages Disadvantages
• greater capacity (bandwidth of up to
2 Gbps)
• Speed (100 - 500 mbps)
• smaller size and lighter weight
• lower attenuation
• immunity to environmental
interference
• highly secure
• Electromagnetic isolation
• expensive over short distance
• requires highly skilled installers
• adding additional nodes is
difficult
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