This document outlines the course objectives and structure for an optical fiber communications systems course at Taiz University in Yemen. The course aims to help students understand optical components, fiber propagation characteristics, system design, and optical networks. It assumes a background in communication systems and electronic devices. The course will cover topics like light propagation, transmission characteristics, optical sources, detectors, noise, and photonic networks. It will be assessed through a midterm, final exam, and course assignments.
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►To understand operation of optical
components which are utilized in
communication systems and networks.
►To understand optical fiber propagation
characteristics and transmission
properties.
►To design and analysis the optical fiber
communication systems.
►To overview the optical networks and its
applications.
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►It assumes students have a
background in
Communication Systems
Electronic Devices.
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• Text Book:
Optical Fiber Communications Principles and
Practice by J. Senior, 2009.
• References:
Introduction to Fiber Optics by J. Crisp, 2005.
Fiber Optic Communications by Joseph C Palais,
2005.
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Grade Date
Test 1 30 5th week
Final Exam 120
Total 150
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• Introduction
• Light Propagation In Optical Fiber
• Transmission Characteristics of Optical
Fibers
• Optical sources
• Optical detectors
• Noise
• Basic System Design
• Photonic and optical network
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History (10 greatest communications inventions)
1. Cable Communications
2. The Telephone
3. Radio
4. Television
5. Satellite
6. Fiber Optics
7. The Mobile Phone
8. The Internet
9. The Wireless Internet
10. Converged Devices
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Throughout the world fiber optics is now being
used to transmit voice, video, and data signals
by light waves over flexible hair-thin threads of
glass or plastics. Its advantages in such use, as
compared to conventional coaxial cable or
twisted wire pairs, are fantastic. As a result,
light-wave communication systems or fiber
optics communication systems are one of the
important feature for today's communications.
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EM-Spectrum
extend from 10 Hz
to 1025 Hz.
All EM radiations
travel in free space
with constant
velocity of 3 x 108
m/s.
Optical radiation
lies between radio
waves and x-rays
on the spectrum.
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• Frequency multiples of 50 GHz or 100 GHz
• λ = c/f c = 299792458 m/s
• λ [nm] = 299792.458/f [THz]
f = 195.0 THz → λ = 1537.397 nm = 1.5374 µm
f =195.1 THz → λ = 1536.609 nm = 1.5366 µm
f =195.2 THz → λ = 1535.822 nm = 1.5358 µm
f =193.4 THz → λ = 1550.116 nm = 1.5501 µm
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• Transmission Medium, or channel, is the actual
physical path that data follows from the
transmitter to the receiver.
• Copper cable is the oldest, cheapest, and the
most common form of transmission medium to
date.
• Optical Fiber is being used increasingly for high-
speed and long-distance applications.
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Transmission by Light: why?
• Growing demand for faster and more efficient
communication systems
• Internet traffic is tripling each year
• It enables the provision of Ultra-high
bandwidth to meet the growing demand
• Increased transmission length
• Improved performance
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Typical data bandwidth requirement
– Raw text = 0.0017 Mb
– Word document = 0.023 Mb
– Word document with picture = 0.12 Mb
– Radio-quality sound = 0.43 Mb
– Low-grade desktop video = 2.6 Mb
– CD-quality sound = 17 Mb
– Good compressed (MPEG1) video = 38 Mb
– Good compressed (MPEG4) video = 700 Mb
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0
20000
40000
60000
1990 2000 2010 2020
Bandwidth Demand (Mbps)
Bandwidth
Demand (Mbps)
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Development
Year
Laser lifetime extended to 7000 hours using AIGaAs operating at 0.8
µm and 0.9µm. Other materials emitting light at 1.1µm to 1.6µm was
found.
1977
Japan, Graded index multi-mode fibre
-Bandwidth: 20 GHz, but only 2 GHz/km
-Start of fibre deployment
1976
- 1300 nm Single mode fibre @ 100 Gbps/km
- 1500 nm Single mode fibre @ 1000 Gbps/km
- Erbium Doped Fibre Amplifier
1980’S
- Optical amplifiers
- Wavelength division multiplexing,
- Optical time division multiplexing (experimental) OTDM
1990’S
- Optical Networking
- Dense WDM, @ 40 Gbps/channel, 10 channels
- Hybrid DWDM/OTDM
2000’S
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• At present the minimum attenuation for glass
fibers is reported to be 0.2 dB/km. There are
1.5µm systems operating with repeater spacing
of 150km.
• Alcatel has unrepeatered systems of 2.5 Gb/s and
622 Mb/s spanning distance of 3200 km and 3500
km respectively.
• WDM systems operating at 1.28 Tbit/s (128
wavelengths at 10.7 Gbit/s (Lucent Technology) is
possible today.
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• An optical fiber communication system is similar in basic concept to any
type of communication systems.
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(a) The general communication system. (b) The optical fiber communication system
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• Information source provides electrical signal to the transmitter
comprising of an electrical stage which drives an optical source to
modulate the light wave carrier.
• The optical source which converts electrical to optical signal may
be either a semiconductor injection laser diode (ILD) or light
emitting diode (LED).
• Transmission medium consists of an optical fiber cable and the
receiver consists of an optical detector which drives a farther
electrical stage and hence provides demodulation of the optical
earner.
• Photodiodes (p-n, p-i-n, or avalanche) are utilized for the detection
of the optical signal or the optical to electrical conversion.
• At present the signal processing is usually performed electrically.
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A digital optical fiber link using a semiconductor laser source and an
avalanche photodiode (APD) detector
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• A serial bit stream in electrical form is presented to a
modulator, which encodes the data appropriately for fiber
transmission
• A light source (laser or Light Emitting Diode - LED) is driven by
the modulator and the light focused into the fiber
• The light travels down the fiber (during which time it may
experience dispersion and loss of strength)
• At the receiver end the light is fed to a detector and converted
to electrical form
• The signal is then amplified and decoded to restore the
original bit stream
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• High data rate, low transmission loss and low
bit error rates
The optical carrier frequency in the range 1013 to
1016 Hz yields a far greater potential transmission
bandwidth than metallic cable systems (i.e.
coaxial cable bandwidth up to around 500 MHz)
or even millimeter wave radio systems (i.e.
systems currently operating with modulation
bandwidths of 700 MHz).
Potential BW 50 Tbit/s
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• High immunity from electromagnetic
interference and crosstalk
Optical fibers are free from electromagnetic interference
(EMI) and radio frequency interference (RFI). Hence the
operation of an optical fiber communication system is
unaffected by transmission through an electrically noisy
environment and the fiber cable requires no shielding from
EMI. The fiber cable is also not susceptible to lightning
strikes if used overhead rather than underground.
Moreover, it is fairly easy to ensure that there is no optical
interference between fibers and hence, unlike
communication using electrical conductors, crosstalk is
negligible, even when many fibers are cabled together.
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• Small size, light weight, and stronger
Optical fibers have very small diameters which are
often no greater than the diameter of a human hair.
Hence, even when such fibers are covered with
protective coatings they are far smaller and much
lighter than corresponding copper cables. This is a
tremendous boom towards the alleviation of duct
congestion in cities, as well as allowing for an
expansion of signal transmission within mobiles such
as aircraft, satellites and even ships.
RG-19/U 14 dB/km at 100 MHz 1110 kg/km
Silica Fiber 0.2 dB/km 6 kg/km
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The attenuation of a length of RG-19/U coaxial cable is
about 14 dB/km at 100 MHZ. Suppose the input power
to the cable is 10 mW and the receiver sensitivity is
0.001 mW. How long can the coaxial cable be under
these conditions ? If optical fiber is used instead , with
a loss rated at 0.2 dB/km ,how long can the
transmission line be?
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• Signal security
The light from optical fibers does not radiate
significantly and therefore they provide a high degree
of signal security. Unlike copper cables, a transmitted
optical signal cannot be obtained from a fiber in a non-
invasive manner (i.e. without drawing optical power
from the fiber). Therefore, in theory, any attempt to
acquire a message signal transmitted optically may be
detected. This feature is obviously attractive for
military, banking and general data transmission (i.e.
computer network) applications.
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• Electrical isolation
Optical fibers which are fabricated from glass or
sometimes a plastic polymer are electrical
insulators and therefore, unlike their metallic
counterparts, they do not exhibit earth loop and
interface problems. Furthermore, this property
makes optical fiber transmission ideally suited for
communication in electrically hazardous
environments as the fibers create no arcing or
spark hazard at abrasions or short circuits.
Bi-directional signal transmission
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• Low transmission loss
The development of optical fibers has resulted in the
production of optical fiber cables which exhibit very
low attenuation or transmission loss in comparison
with the best copper conductors. Fibers have been
fabricated with losses as low as 0.2 dB km-1 It
facilitates the implementation of communication links
with extremely wide repeater spacing (long
transmission distances without intermediate
electronics). Thus reducing both system cost and
complexity.
RG-19/U 500 MHz 14 dB/km
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• High reliability, and ease of maintenance
These features primarily stem from the low loss property of
optical fiber cables which reduces the requirement for
intermediate repeaters or line amplifiers to boost the
transmitted signal strength. Hence with fewer repeaters,
system reliability is generally enhanced in comparison with
conventional electrical conductor systems. Furthermore, the
reliability of the optical components is no longer a problem
with predicted lifetimes of 20-30 years now quite common.
Both these factors also tend to reduce maintenance time and
costs.
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• Potential low cost
The glass which generally provides the optical fiber
transmission medium is made from sand-not a scarce
resource. So, in comparison with copper conductors,
optical fibers offer the potential for low cost line
communication. Overall system cost when utilizing
optical system optical system are substantially less than
those for equivalent electrical line systems because of
the low loss and wideband properties of optical
transmission.
The main advantages: Large BW and Low loss
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Two major applications:
1. Optical communications systems
– Voice
o Telephone trunk for high data
o Subscriber service
o fiber-to-the home (FTTH)
o broadband services (multimedia, video, etc. )
– Video
o Broadcast Television
o Remote monitoring
o Fiber-guided missile
o Fiber-to-the home
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– Data
• Computers ,CPU to CPU
• Interoffice data links
• Local Area Network (LAN)
• Fiber-to-the home
• Aircraft and ship wiring - reduced weight
• Satellite ground stations
2. Non communication applications
• Sensors (gyroscopes, pressure, temperature, strain etc.)
• Illumination
• Imaging and inspection
• Medical applications
• Broad Optoelectronics
• Electronics and Computers
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