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OPTOELECTRONIC COMMUNICATIONS
EKT 442
1
MEETING
• LECTURE
• LABORATORY
: 3 HOURS
: 2 HOURS
LECTURER
Assoc. Prof. Dr. Syed Alwee Aljunid
017-5872667
[email protected]
2
Textbook
• John Wilson and John Hawkes
“Optoelectronics: An Introduction, 3nd Ed.”
Prentice Hall, 1998.
3
References
•
•
•
Joseph C. Palais “Fiber Optic
Communications, 5th Ed.” Prentice Hall,
2005.
Ghatak and Thyagarajan“ An introduction to
Fiber Optics”, Cambridge University Press,
1998.
John. M. Senoir “Optical Fiber
Communication: Principle and Practise, 2nd
Ed. ”, Prentice Hall, 1993.
4
Assessment
• Final Exam = 50 %
• Coursework = 50 %
– Assignments/Quiz = 10 %
– Tests = 10 %
– Labs/Tutorials = 30 %
5
Syllabus:
1.
2.
3.
4.
5.
6.
7.
Light Properties
Fundamentals of Fiber Optic
Optical Components/Devices
Light Sources
Light Detectors, Noise and Detection
Optical Amplifiers
System Design
6
Chapter 1.0
Light
Properties
7
Contents
a)
b)
c)
d)
Electromagnetic radiation
Frequency and wavelength of light
Refraction of light
Polarization of light
8
Electromagnetic radiation
9
Wavelength range
of electromagnetic transmission
Wavelength
3000km
102
30km
103
104
300m
105
106
NF
range
analog
phone
3m
107
108
HF
range
AM
radio
TV & FM
radio
3cm
109
0.3mm
1010
1011 1012 1013
Microwaves
range
mobile
phone
3 mm
30nm
1014 1015
Optical
range
microwave
oven
0.3nm
1016 1017 1018
Frequency [Hz]
X / gamma
range
X-rays
10
Wavelength range
of optical transmission
wavelength nm
1800
1600
1400
1200
1000
2x1014
Radar
range
Laser
range
800
600
400
3x1014
Infrared
range
1. Optical window
2. Optical window
3. Optical window
200
1x1015
Frequency Hz
Visible
range
5x1014
Ultraviolet
range
850
nm
1300
nm
1550
nm
11
Electromagnetic radiation
Gamma rays,
• highest-frequency electromagnetic energy
• emitted by certain radioactive materials and also
originate in outer space.
• tremendous penetrating ability and able to pass through
three meters of concrete!
12
Electromagnetic radiation
X-rays
• frequency just above ultraviolet
• powerful enough to pass easily through many materials
including soft tissues of animals.
• This has led to the extensive use of X-rays in medicine
to investigate textures in the human body.
13
Electromagnetic radiation
Ultraviolet radiation
• frequencies just above those of visible light
• these rays have enough energy to kill living cells and cause tremendous tissue damage.
• sun is a constant source of ultraviolet radiation
• small doses of this light can promote the production of vitamin D and tan the skin.
• Too much ultraviolet radiation can lead to serious sunburn.
• Ultraviolet light is used extensively in scientific instruments to probe various systems,
and it is also important in astronomical observations of the solar system, galaxy, and
other parts of the universe.
14
Electromagnetic radiation
Infrared radiation
• This type of radiation is associated with the thermal region where visible light is not
necessarily present.
• For example, the human body does not emit visible light but it does emit infrared
radiation which is felt as heat.
• Almost all objects emit infrared rays, depending on the temperature of the object.
Warmer objects emit more infrared radiation than cooler objects.
• Common uses for infrared radiation are night vision scopes, electronic detectors,
sensors in satellites and airplanes, and in astronomy
15
Electromagnetic radiation
Microwave
• The energy spectrum of microwaves has been utilized in oven technology
where the wavelength is tuned to frequencies that are readily absorbed by
water molecules in food causing them to absorb energy and release heat as
they vibrate.
• Microwaves are the highest frequency radio waves and are emitted by the
Earth, buildings, cars, planes, and other large objects.
• Short wavelength microwaves are the basis for RADAR, which stands for
radio detecting and ranging, a technique used in locating large objects and
calculating their speed and distance.
16
Electromagnetic radiation
Radio
• well known for their ability to transmit radio and television signals.
• wide spectrum of electromagnetic radiation
• Radio waves used in communication usually consist of two types of transmissions:
amplitude modulated (AM) waves that vary in the amplitude of the wavelengths and
frequency modulated (FM) waves that vary in wavelength frequency. FM radio
waves are shorter in length than AM waves and tend to be blocked by large objects
such as houses, buildings, and tunnels. AM waves are longer than FM waves and
can be bent around these large objects to improve reception.
17
Electromagnetic radiation
Visible light
• comprises only a tiny portion of the entire electromagnetic
spectrum of radiation.
• The wavelengths that we are able to see lie between 400 and 700
nanometers in length.
18
Electromagnetic radiation
Visible Light Wavelength and Perceived Color
Wavelength Range
(nanometers)
Perceived Color
340-400
Near Ultraviolet (UV; Invisible)
400-430
Violet
430-500
Blue
500-560
Green
560-620
Yellow to Orange
620-700
Orange to Red
Over 700
Near Infrared (IR; Invisible)
19
Frequency and wavelength of light
electrons moving in orbits around the
nucleus of an atom are arranged in different
energy levels within their electron clouds.
20
Frequency and wavelength of light
These electrons can absorb additional energy from
outside sources of electromagnetic radiation, which
results in their promotion to a higher energy level or
electron cloud.
21
Frequency and wavelength of light
higher energies are associated with shorter
wavelengths and lower energies are associated
with higher wavelengths
22
Light propagation
Water tank
Expected way of the light
Light
source
Effective way
of the light
Total reflection at the boundary water-air
23
Speed of light
Vacuum
Milan
1 Millisecond
Zuric
h
Glas
Milan
1,5 Millisecond
 Speed of light in vacuum:
C0 = 299’793 km/sec.
 Speed of light in glass:
Cglass = 200’000 km/sec.
Zurich
24
Wavelength / Frequency
1 Sek.
f
Wavelength
(nm)
covered distance of a
wave during one period
(oscillation)
Frequency
t
Frequency
(Hz)
Number of oscillations
(period per second)
Wavelength
25
Frequency and wavelength of light
Relationship between
wavelength and frequency of
light
n = c/l
Where:
c is the speed of light
n is the frequency of the light in hertz (Hz)
l is the wavelength of the light in meters
wavelength of light in inversely proportional to the
frequency
26
Frequency and wavelength of light
relationship between the energy of a photon and it's frequency
E=h n
E = h (c/ l)
Where:
E is the energy in kiloJoules per mole
h is Planck's constant with a value of
6.626 x10-34 Joule-seconds per particle
energy of a photon is directly proportional to its frequency and inversely
proportional to its wavelength
27
Frequency and wavelength of light
Conclusion
•
Very high-frequency electromagnetic radiation such a gamma rays, x-rays, and
ultraviolet light possess very short wavelengths and a great deal of energy.
•
On the other hand, lower frequency radiation such as visible, infrared,
microwave, and radio waves have correspondingly greater wavelengths with
lower frequencies and energy.
28
Nature of light
29
Nature of light
30
Nature of light
31
Nature of light
32
Nature of light
33
Reflection
Perpendicular
to division line
Division line
Light path
Light path
Division line
Light
reflection
Total
reflection
Perpendicular
to division line
34
Light propagation in glass fiber
Optical thinner
Medium (n2)
Light refraction
Border ray
Optical denser
Medium (n1)
Total reflection
Light source
35
Reflection of light
36
Refraction of light
Refraction (or bending of the light) occurs as light passes from a one medium to another when there is a
difference in the index of refraction between the two materials, and is responsible for a variety of familiar
phenomena such as the apparent distortion of objects partially submerged in water.
When light passes from a less dense medium (such as air)
to a more dense medium (such as water), the speed of the wave decreases.
37
Refraction of light
Refractive index is defined as the relative speed at which light moves through a material with
respect to its speed in a vacuum. By convention, the refractive index of a vacuum is defined as
having a value of 1.0. The index of refraction, N (or n), of other transparent materials is defined
through the equation:
Material
Refractive Index
Air
1.0003
Water
1.33
Glycerin
1.47
Immersion Oil
1.515
Glass
1.52
Flint
1.66
Zircon
1.92
Diamond
2.42
Lead Sulfide
3.91
38
Refraction of light
When light passes through a medium of high refractive index into a medium of lower
refractive index, the incident angle of the light waves becomes an important factor.
If the incident angle increases past a specific value (dependent upon the refractive index of the two media), it
will reach a point where the angle is so large that no light is refracted into the medium of lower refractive
index,
39
Refraction of light
This phenomenon takes place when the angle of refraction (angle r in Figure 4) becomes
equal to 90 degrees and Snell's law reduces to:
When the critical angle is exceeded for a particular wave, it exhibits total
reflection back into the medium.
40
Refraction of light
Another important feature of light refraction, is that the wavelength of light has an impact on the amount of refraction in
the same material. The amount of refraction is inversely proportional to the wavelength..
Thus, shorter wavelength visible light is refracted at a greater angle than longer wavelength light. White light is
composed of all the colors in the visible spectrum. When this light is passed through a glass prism, the white light is
dispersed into its component colors in a manner that is dependent upon the individual wavelengths
41
Polarization of light
42
Diffraction of light
43
Difraction of light
44
Difraction of light
45
Polarization of light
46
Polarization of light
47
Polarization of light
48
Polarization of light
49
Brewster’s(Critical) angle
50
Thank You
51