7.1

Chapter 7

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Transmission Media

7.2

Figure 7.1 Transmission medium and physical layer

7.3

Figure 7.2 Classes of transmission media

7.4

7-1 GUIDED MEDIA

Guided media, which are those that provide a conduit from one device to another, include twisted-pair cable, coaxial cable, and fiber-optic cable.

Twisted-Pair Cable�Coaxial Cable�Fiber-Optic Cable

Topics discussed in this section:

7.5

Figure 7.3 Twisted-pair cable

7.6

Figure 7.4 UTP and STP cables

7.7

Table 7.1 Categories of unshielded twisted-pair cables

7.8

Figure 7.5 UTP connector

7.9

Figure 7.6 UTP performance

7.10

Figure 7.7 Coaxial cable

7.11

Table 7.2 Categories of coaxial cables

7.12

Figure 7.8 BNC connectors

7.13

Figure 7.9 Coaxial cable performance

7.14

Figure 7.10 Bending of light ray

7.15

Figure 7.11 Optical fiber

7.16

Figure 7.12 Propagation modes

7.17

Figure 7.13 Modes

7.18

Table 7.3 Fiber types

7.19

Figure 7.14 Fiber construction

7.20

Figure 7.15 Fiber-optic cable connectors

7.21

Figure 7.16 Optical fiber performance

7.22

7-2 UNGUIDED MEDIA: WIRELESS

Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication.

Radio Waves

Microwaves

Infrared

Topics discussed in this section:

7.23

Figure 7.17 Electromagnetic spectrum for wireless communication

7.24

Figure 7.18 Propagation methods

7.25

Table 7.4 Bands

7.26

Figure 7.19 Wireless transmission waves

7.27

Figure 7.20 Omnidirectional antenna

7.28

Radio waves are used for multicast communications, such as radio and television, and paging systems.

7.29

Figure 7.21 Unidirectional antennas

7.30

�Microwaves are used for unicast communication such as cellular telephones, satellite networks,�and wireless LANs.

7.31

�Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation.