Transcript Chapter 1-Introduction

CHAPTER 1
Optoelectronics Communications
School of Computer and Communication Engineering,
University Malaysia Perlis (UniMAP)
EKT 442: Optoelectronics
Coursework Contribution
1. COURSE IMPLEMENTATIONS
I)Lecture
 3 hours per week for 14 weeks (Total = 42 hours)
II)Laboratory
 2 hours per week for 14 weeks (Total = 28 hours)
Laboratory assignment
30%
Test 1&2
20 %
Final Exam
50%
Total
100%
Lecturer: Mr. Hilal A. Fadhil
Office: 1st Floor, House #8A, KKF 34, K.wei- Kuala Perlis
E-mail: [email protected]
Office tel#: 04-9852639
HP#: Upon Request
Teaching Engineer: Mr. Matnor+ Ms. Fazilna, [email protected]
Office: House #A4, KKF 33, Kuala Perlis
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Course material
Course text book:
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“Gerd Keiser, Optical Fiber Communications,
3rd Edition, Mc Graw Hill, 2000
Reference Books:
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Joseph C. Palais, Fiber Optic Communications, 5th
Edition, Prentice Hall, 2005
Jeff Hecht, Undestanding Fiber Optics, 5th Edition,
Prentice Hall, 2006
Course Outcome
Chapter 1-Introduction:
Chapter 2: Light Propagation & Transmission Characteristics of Optical Fiber
Chapter 3: Optical Components/ Passive Devices
Chapter 4: Optical Sources
Chapter 5: Light Detectors, Noise and Detection
Chapter 6: SYSTEM DESIGN
Introduction
For years fiber optics has been merely a system for piping light
around corners and into in accessible places so as to allow the hidden to be
seen. But now, fiber optics has evolved into a system of significantly greater
importance and use. Throughout the world it 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 of fiber optics communication system are one of the
important feature for today’s communication.
What are the features of a optical communication system?
Why “optical ” instead of “copper wire ”?
A History of Fiber Optic Technology
The Nineteenth Century
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John Tyndall, 1870
– water and light experiment
– demonstrated light used
internal reflection to follow a
specific path
William Wheeling, 1880
– “piping light” patent
– never took off
Alexander Graham Bell, 1880
– optical voice transmission
system
– called a photophone
– free light space carried
voice 200 meters
Fiber-scope, 1950’s
The Twentieth Century
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Glass coated fibers developed to reduce optical loss
Inner fiber - core
Glass coating - cladding
Development of laser technology was important to fiber
optics
Large amounts of light in a tiny spot needed
1960, ruby and helium-neon laser developed
1962, semiconductor laser introduced - most popular type
of laser in fiber optics
core
cladding
The Twentieth Century (continued)
• 1966, Charles Kao and Charles Hockman proposed optical fiber could be
used to transmit laser light if attenuation could be kept under 20dB/km
(optical fiber loss at the time was over 1,000dB/km)
• 1970, Researchers at Corning developed a glass fiber with less than a
20dB/km loss
• Attenuation depends on the wavelength of light
Optical Wavelength Bands
Short
band
C-band: Conventional Band
L-band: Long Band
Fiber Optics Applications
• Military
– 1970’s, Fiber optic telephone link installed aboard the U.S.S.
Little Rock
– 1976, Air Force developed Airborne Light Fiber Technology
(ALOF)
• Commercial
– 1977, AT&T and GTE installed the first fiber optic telephone
system
– Fiber optic telephone networks are common today
– Research continues to increase the capabilities of fiber optic
transmission
Applications of Fiber Optics
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Military
Computer
Medical/Optometric
Sensor
Communication
Military Application
Computer Application
Sensors
Gas sensors
Chemical sensors
Mechanical sensors
Fuel sensors
Distance sensors
Pressure sensors
Fluid level sensors
Gyro sensors
Medical Application
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Endoscope
Eyes surgery
Blood pressure meter
The Future
• Fiber Optics have immense potential bandwidth
(over 1 teraHertz, 1012 Hz)
• Fiber optics is predicted to bring broadband services
to the home
– interactive video
– interactive banking and shopping
– distance learning
– security and surveillance
– high-speed data communication
– digitized video
Fiber Optic Fundamentals
Advantages of Fiber Optics
• Immunity from Electromagnetic
(EM) Radiation and Lightning
• Lighter Weight
• Higher Bandwidth
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Better Signal Quality
Lower Cost
Easily Upgraded
Ease of Installation
The main advantages:
Large BW and Low loss
Immunity from EM radiation and Lightning:
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Fiber is made from dielectric (non-conducting)
materials, It is un affected by EM radiation.
- Immunity from EM radiation and lightning most
important to the military and in aircraft design.
- The fiber can often be run in same conduits that
currently carry power, simplifying installation.
Lighter Weight:
- Copper cables can often be replaced by fiber optic
cables that weight at least ten times less.
- For long distances, fiber optic has a significant
weight advantage over copper cable.
Higher Bandwidth
- Fiber has higher bandwidth than any alternative
available.
- CATV industry in the past required amplifiers every
thousand feet, when copper cable was used (due to
limited bandwidth of the copper cable).
- A modern fiber optic system can carry the signals up
100km without repeater or without amplification.
Better Signal Quality
- Because fiber is immune to EM interference, has
lower loss per unit distance, and wider bandwidth,
signal quality is usually substantially better compared
to copper.
Lower Cost
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Fiber certainly costs less for long distance applications.
The cost of fiber itself is cheaper per unit distance than copper if
bandwidth and transmission distance requirements are high.
Principles of Fiber Optic Transmission
• Electronic signals converted to light
• Light refers to more than the visible portion of the electromagnetic
(EM) spectrum
Optical power Measurement units:
In designing an optical fiber link, it is of interest to establish, measure the signal
level at the transmitter, at the receiver,, at the cable connection, and in the cable.
Power: Watt (W), Decibel (dB), and dB Milliwatt (dBm).
dB: The difference (or ratio) between two signal levels. Used to describe the effect of system
devices on signal strength. For example, a cable has 6 dB signal loss or an amplifier has 15 dB of
gain.
 PowerOut 
 dB
Gain  10 log 
Power
In 

dBm: A signal strength or power level. 0 dBm is defined as 1 mW (milliWatt) of power into a
terminating load such as an antenna or power meter.
The Electromagnetic Spectrum
- Light is organized into what is known as the
electromagnetic spectrum.
- The electromagnetic spectrum is composed of visible
and near-infrared light like that transmitted by fiber
and all other wavelengths used to transmit signals
such as AM and FM and television.
Principles of Fiber Optic Transmission
• Wavelength - the distance a single cycle of an
EM wave covers
• For fiber optics applications, two categories of
wavelength are used
– visible (400 to 700 nanometers) - limited use
– near-infrared (700 to 2000 nanometers) - used
almost always in modern fiber optic systems
Elements of an Optical Fiber communication
• Fiber optic links contain three basic elements
– transmitter
– optical fiber
– receiver
Optical Fiber
User
Input(s)
Transmitter
Electrical-to-Optical
Conversion
Receiver
User
Output(s)
Optical-to-Electrical
Conversion
• Transmitter (TX)
– Electrical interface encodes user’s information through AM,
FM or Digital Modulation
– Encoded information transformed into light by means of a
light-emitting diode (LED) or laser diode (LD)
User
Input(s)
Electrical
Interface
Data Encoder/
Modulator
Light
Emitter
Optical
Output
• Receiver (RX)
– decodes the light signal back into an electrical signal
– types of light detectors typically used
• PIN photodiode
• Avalanche photodiode
• made from silicon (Si), indium gallium arsenide (InGaAs)
or germanium (Ge)
– the data decoder/demodulator converts the signals into the
correct format
Optical
Input
Light Detector/
Amplifier
Data Decoder/
Demodulator
Electrical
Interface
User
Output(s)
• Transmission comparison
– metallic: limited information and distance
– free-space:
• large bandwidth
• long distance
• not private
• costly to obtain
useable spectrum
– optical fiber: offers
best of both
Fiber Optic Components
• Fiber Optics Cable
• Extremely thin strands of ultra-pure glass
• Three main regions
– center: core (9 to 100 microns)
– middle: cladding (125 or 140 microns)
– outside: coating or buffer (250, 500 and 900 microns)
A FIBER STRUCTURE
Light Emitters
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Two types
– Light-emitting diodes
(LED’s)
• Surface-emitting
(SLED): difficult to
focus, low cost
• Edge-emitting (ELED):
easier to focus, faster
– Laser Diodes (LD’s)
• narrow beam
• fastest
Detectors
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Two types
– Avalanche photodiode
• internal gain
• more expensive
• extensive support electronics required
– PIN photodiode
• very economical
• does not require additional support circuitry
• used more often
Interconnection Devices
• Connectors, splices, couplers, splitters, switches, wavelength
division multiplexers (WDM’s)
• Examples
– Interfaces between local area networks and devices
– Patch panels
– Network-to-terminal connections
Manufacture of Optical Fiber
Introductions
• 1970, Corning developed new process called inside vapor
deposition (IVD) to first achieve attenuation less than 20dB/km
• Later, Corning developed outside vapor deposition (OVD) which
increased the purity of fiber
• Optical fiber was developed that exhibits losses as low as
0.2dB/km (at 1550nm). This seemed to be adequate for any
application.
• As the Internet expanded, more capacity was needed.
Electronics can handle about 40Gbps, but not much more.
Researchers developed Dense Wavelength-Division
Multiplexing (DWDM) - 80 or more simultaneous data streams
can now be combined on a single fiber, each being transmitted
at a slightly different color of light
Manufacture of Optical Fiber - MCVD
• Modified Chemical Vapor Deposition (MCVD)
– another term for IVD method
– vaporized raw materials are deposited into a pre-made silica
tube
Cont…
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Widely adopted to produce very low – loss graded – index fibers.
The glass vapor particles, arising from the reaction of the constituent metal halide
gases and oxygen, flow through the inside of a revolving silica tube.
As the SiO2 particles are deposited, they are sintered to a clear glass layer by an
oxyhydrogen torch which travels back and forth along the tube.
When the desired thickness of glass has been deposited, the vapor flow is shut off
and the tube is heated strongly to cause it to collapse into a solid rod preform.
The fiber that is subsequently drawn from this preform rod will have a core that
consists of the vapor deposited material and a cladding that consists of the original
silica tube.
Manufacture of Optical Fiber - OVD
• Outside Vapor Deposition (OVD)
– vaporized raw materials are deposited on a rotating rod
– the rod is removed and the resulting perform is consolidated by heating