Guided Transmission Media
• Twisted Pair
• Coaxial cable
• Optical fiber
Transmission Characteristics of Guided Media
|
Transmission Media |
Diameter |
Band Width |
Data Rate |
Repeater Spacing
|
Typical Delay
|
Frequency Range
|
|
Twisted Pair |
|
|
|
|
|
|
|
Coaxial Cable |
0.4 – 1 inch |
350 MHz |
500 Mb/s |
1 – 10 Km |
4 µs/km
|
0 – 500 MHz |
|
Optic Fiber |
2-125 µm |
2 GHz |
2 Gb/s |
10 – 100 Km |
5 µs/km
|
186-370 THz |
Data rate
Rate of data transmission in bits per second
Repeater Spacing
Depends upon the field of electromagnetic waves. If the cable is near telephone or electrical wires then repeater should be closely fitted.
Giga = 109
Tera = 1012
BandWidth
The difference between the highest and lowest frequencies that an analog communications system can pass as measured in Hertz (Hz) or cycles per second. For example, a telephone accommodates a bandwidth of 3,000 Hz: the difference between the lowest (300 Hz) and highest (3,300 Hz) frequencies it can carry.
Twisted Pair
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)
Twisted Pair – Pros and Cons
• Cheap
• Easy to work with
• Low data rate
• Short range
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)
Coaxial Cable
© Outer conductor is a braided shield.
© Inner conductor is solid metal.
© Separated by insulated material.
© Covered by padding.
© Co = Common , Axial = Axis
Optical Fiber
Optic = light
Fiber = thread ( very delicate that’s why known as thread ). Data travel with speed of light. It’s a glass tube. Jacket = plastic, cladding = protective layer.
If it’s kept straight then there would be no loss of data, to stop bending we use arms.
To stop the data loss light is injected in a specific angle, this is known as total internal reflection.
This angle of reflection is known as Critical angle, which for water is 42°&° for glass it’s 57°
Optical Fiber – Benefits
N Greater capacity
N Smaller size & weight
N Electromagnetic isolation
N Greater repeater spacing
Optical Fiber – Applications
N Long-haul trunks
N Metropolitan trunks
N Rural exchange trunks
N Subscriber loops
N LANs
LED( Light Emitting Diode ) & ILD ( Injection Laser Diode) are used to convert electrical signal into
light signal.
TRANSDUCER:
Device which convert energy from one form to other form e,g fan is Transducer.
LED & ILD are electrical to optical ( E/O )transducer & photodiode (solar cell) are O/E transducer.
Electrical signal à (e/o) light à(o/e) electric .
Optical Fiber Transmission Modes