16-02-2013, 10:35 AM
Data Transmission and Media
Data Transmission.ppt (Size: 324.5 KB / Downloads: 43)
Guided media: Twisted pair:
Applications: LAN, Telephones
Twist decreases crosstalk
Tighter the twists, the better the cable
Bundled pairs vary twist rate
Most common medium
Telephones, 10 Base-T, 100 Base-T, ISDN
Inexpensive, flexible, easy to work
Useful for shorter applications
Useful to 100 Mbps (1 GHz for CAT7)
Guided cable: optical fiber
Thin, flexible medium made from glass (fused silica) or plastic capable of conducting ultra-high frequency signals (light)
Ultra-pure fiber: best performance-highest cost
Multicomponent glass: moderate/moderate
Plastic: low/least
Cylindrical with 3 concentric sections: the core, the cladding, the jacket
Optical fiber:
Long trunks: 900 miles, high capacity (20K to 60K voice channels)
Metropolitan trunks: 8 miles, 100K voice channels, no repeaters, connect telephone exchanges to each other and to backbone
Rural exchange trunks: 25-100 miles, link towns and different telco’s (5K voice channels)
Subscriber loop trunks: central exchange to subscriber
LAN’s: 100 Mbps, price is attractive
Mediums
Fiber Optics
use total internal reflection
This occurs in a transparent medium whose index of refraction is higher that surrounding medium