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Module 4: Telecommunications Engineering - Coggle Diagram
Module 4: Telecommunications Engineering
History
Telephone
Modulation
Telegram
Materials
Testing
Fibre Optics
Long thin cables of glass that transmit light that is received as electric signals
Manufacture
Layers
Core
Glass center
Cladding
outer optical material with a differing reflective index that causes the light to reflect back into the wire
Graded Index
Step up Index
Buffer material
Insulator/protective material for the cable
Modern Way
Modifired Chemical Vapour Depositition
Oxygen bubbled through germanium and silicon chloride
Protection flowchart tower
Modes
Single mode
Small Cores & transmit infra red light
Allows only 1 path of light reflection
Better capacity range and lower attenuation
Multi Mode
Larger cores but shorter infra red light wave lengths
For LEDs - LIght Emitting Diode
Multiple modes of light reflection
As light may take a longer path not all light arrive same time
intermodal dispersion
Cheaper
As light bounces across the cable - the light signal might degrade
Longer Wavelength less degradation
FO systems
Optical Fiber
trasnmits signal
Optical Regenerator
Boosts signal
Transmitter
produce and encode signal
Optical Reciever
Recieves and decodes signal
Why Better than normal wires
Higher signal capacity
Less signal degradation
thinner
Cheaper
Less power
Good for digital
Non Flammable
Good for long distances
Not affected by EM interference
Testing of Optics
Tensile strength
Attenuation
Carrying capacity
Operating Temperature and Humidity
Ability for underwater transmission
Total internal reflection
Physics Total internal reflection angle angle from perpendicular for which light fully reflects back into core
Fiber optic reflection angle is from internal middle axis of core there fore FO angle = 90 - Physics angle
Critical angle is angle for which the light passes directly across the two mediums
Semi Conductors
Silicon
Germanium
Doping
Types
N
Doping Material
Phosphorous & Arsenic
P
Doping Material
Boron & Gallium
Junctions
When P and N Types together creates a diode
Diodes
Diodes only allow current to go one way and not the other
Ideal Diode allows no current through but realistic diodes allow about 10mA through and have a breakdown voltage
Breakdown voltage is a large reversed voltage that which current can flow through unlike normal semiconductor behaviour
Transistors
3 layers of Semiconductors PNP or NPN
acts as a switch or to amplifiy
If a small amount of current added to centre of sandwich a larger current can pass through the junction
N close to + terminal and P close to negative terminal
No current can flow as holes in P move toward - and electrons go to +
Switched current flows fine as Holes repelled by + and electrons repelled by - terminal
Communication
Electronics