Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Title: Communication sysystem
Description: Fiber optic communication in our generation
Description: Fiber optic communication in our generation
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Dar es Salaam institute of Technology (DIT)
ETT 06208/ETD 602
Communication Systems
Ally, J
jumannea@gmail
...
With optical fibers, electromagnetic waves are guided
through a media composed of a transparent material
without using electrical current flow
...
DIT
An optical communication systems
An optical communication systems is one that uses light as
the carrier of information
...
Optical fiber cables have, for all practical purposes, an
infinite bandwidth
...
Light frequencies used in optical fiber communication
systems are between 1x1014Hz and 4x1014Hz
(100,000GHz to 400,000GHz)
...
DIT
Transmission Media
Twisted Pair
Coaxial Cable
10 megabit/sec (Mb/s)
110 kilometers
100 megabit/sec
110 kilometers
Optical fiber
Digital Microwave Radio
100 megabit/sec
10100 kilometers
DIT
Fiber Optic
Transmission Systems
Multimode: 100 megabit/sec
Singlemode: 10,000+ megabit/sec
1010010,000 kilometers
Optical Fiber Cables
DIT
Optical Fibers
Fibers of glass
usually 120 micrometers in diameter
Used to carry signals in the form of light over
distances up to 50 km
...
DIT
Parts of Optical Fibers
Core–thin glass center of the fiber where light travels
...
Buffer Coating–plastic coating that protects the fiber
...
DIT
Disadvantages of Optical Fiber
Interfacing costs
Lower tensile strength
Needs more expensive optical transmitters and
receivers
More difficult and expensive to splice than the
metallic wires
More qualified and experienced persons are
required for maintenance and handling
Optical fiber cables are more susceptible to losses
introduced by bending the cable
Need specialized tools, equipment and training
DIT
Areas of Application
Telecommunications
Local Area Networks
Cable TV
CCTV
Optical Fiber Sensors
DIT
Optical Fiber Architecture
DIT
Transmitter (from E to O)
Transmitter use Laser / LED as signal source
Optical fiber transmission is in the infrared regions
Wavelength longer than visible light around 0
...
3dB/km
Attenuated by 7% /km
Diameter: (Example) 2
...
6dB/km
Attenuated by 99
...
4 mm, Weight: 1,110 kg/km
DIT
Long-distance and Capacity (2/3)
Capacity (Bandwidth): 800nm to 1700nm at attenuation < 3dB/km
Frequency(Hz):f, Light speed (m/sec) :C0, Wavelength:λ (m)
λ
f=
C0
, (C0= 3
...
00x108
λ= 800nm
800x109
3
...
5 microns in diameter) and transmit infra-red
light from LED
MMF
SMF
Clad
Core
DIT
Fiber Types(2)
Multi-mode fibers are further categorized as:
Multimode stepindex fiber
Discussed in previous slide, has constant refractive index
throughout the core
...
This theory is known as Planck’s Law, which states, “When
visible light or high frequency electromagnetic radiation
illuminates a metallic surface, electrons are emitted
...
Planck’s Law is expressed mathematically as Ep = hf
where Ep = energy of the photon
h = Planck’s constant = 6
...
Refractive index is a ratio of the speed of light in a material
to the speed of light in free space, it does not have any
units
...
The angle of refraction can be
larger or smaller than the angle of
incidence, depending on the
refractive indexes of the two
materials
...
If the angle of refraction is 900 or greater, the light ray is not allowed to
penetrate the less dense material
...
Critical angle represent mathematically as
n2
sin θ 1 =
sin θ 2
n1
with θ2=900, θ1 becomes the
Critical angle (θc), and
n2
n2
−1 n2
sinθc = (1) ⇒sinθc = ⇒θc = sin
n
n1
n1
1
DIT
Example
A light ray is traveling in a transparent material of
refractive index 1
...
46
...
Solution:
Using the formula for the critical angle just derived:
Put in the values of the refractive indices:
Divide the two numbers:
So:
DIT
How Does Optical Fiber Transmit Light?
Using principle of Total Internal Reflection
Fiber Optics Relay Systems has
-Transmitter
-Optical Fiber
-Optical Regenerator
-Optical Receiver
DIT
Total Internal Reflection
It is an optical phenomena that occurs when a ray of light strikes a
medium boundary at an angle larger than the critical angle with
respect to the normal to the surface
...
However, if the light approaches the boundary at an angle greater
than the critical angle, the light is actually reflected from the boundary
region back into the first material
...
This effect is called total internal reflection (TIR)
...
DIT
Total Internal Reflection(2)
DIT
Testing of Optical Fiber
Tensile Strength
Refractive Index Profile
Fiber Geometry
Information Carrying Capacity
Operating temperature/humidity range
Ability to conduct light under water
Attenuation
DIT
Optical Fiber System Link Budget
As with any communication system, optical fiber systems
consists of a source and a destination that are separated
by numerous components and devices that introduce
various amount of loss or gain to the signal as it
propagates through the system
...
A repeaterless system consists of a light source, such as
an LED or ILD, and a light detector, such as an APD
connected by optical fiber and connectors
...
DIT
Optical Fiber Communication Systems
Without repeater
With repeater
DIT
Main Elements in Photonic Layer
λ1
λ2 ・・・
λn
WDM Terminal
Σλ
Wideband Optical Amplifier
Σλ
λ1
・・・λ2
λn
Σλ
Σλ
Optical Add/Drop Multiplexer
(OADM)
Σλ
Σλ
λi
λj
Wavelength MUX/DEMUX
Simultaneous amplification of
WDM signal
Signal Add/Drop
Transmission capacity control
λi
Optical CrossConnect
(OXC)
Network restoration
Network management
λi
λj
All optical regeneration
Wavelength conversion
λi
Optical Processing
λi
DIT
Basic Network Configurations
(TwoFiber) Ring Network
(Full) Mesh Network
Star Network
Tree Network
Main
Main
DIT
Main
Thanks!
Technology changes but communication lasts
Title: Communication sysystem
Description: Fiber optic communication in our generation
Description: Fiber optic communication in our generation