1 optoelectronic communications ekt 442. 2 meeting lecture : 3 hours laboratory : 2 hours lecturer...
TRANSCRIPT
1
OPTOELECTRONIC COMMUNICATIONS
EKT 442
2
MEETING • LECTURE : 3 HOURS• LABORATORY : 2 HOURS
LECTURERAssoc. Prof. Dr. Syed Alwee [email protected]
3
TextbookTextbook
• John Wilson and John Hawkes “Optoelectronics: An Introduction, 3nd Ed.” Prentice Hall, 1998.
4
ReferencesReferences• 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.
5
AssessmentAssessment
• Final Exam = 50 %
• Coursework = 50 %– Assignments/Quiz = 10 %– Tests = 10 % – Labs/Tutorials = 30 %
6
Syllabus:Syllabus:1. Light Properties2. Fundamentals of Fiber Optic3. Optical Components/Devices4. Light Sources5. Light Detectors, Noise and Detection 6. Optical Amplifiers7. System Design
7
Chapter 1.0 Chapter 1.0
Light Properties
8
ContentsContents
a)Electromagnetic radiationb)Frequency and wavelength of lightc) Refraction of lightd)Polarization of light
9
Electromagnetic radiationElectromagnetic radiation
10
analogphone
AMradio
mobilephone
microwave oven
X-rays
Wavelength
Frequency [Hz]102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018
3000km 30km 300m 3m 3cm 0.3mm 3 mm 30nm 0.3nm
NFrange
HFrange
Microwavesrange
Opticalrange
X / gammarange
TV & FMradio
Wavelength range of electromagnetic transmission
Wavelength range of electromagnetic transmission
11
Frequency Hz
1800 1600 1400 1200 1000 800 600 400 200
2x1014 3x1014
5x1014
1x1015
Infraredrange
Ultravioletrange
wavelength nm
Visible range
1. Optical window 850 nm
2. Optical window 1300 nm
3. Optical window 1550 nm
Laserrange
Radarrange
Wavelength range of optical transmission
Wavelength range of optical transmission
12
Electromagnetic radiationElectromagnetic 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!
13
Electromagnetic radiationElectromagnetic 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.
14
Electromagnetic radiationElectromagnetic 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.
15
Electromagnetic radiationElectromagnetic 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
16
Electromagnetic radiationElectromagnetic 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.
17
Electromagnetic radiationElectromagnetic 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.
18
Electromagnetic radiationElectromagnetic 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.
19
Electromagnetic radiationElectromagnetic 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)
20
Frequency and wavelength of light
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.
21
Frequency and wavelength of light
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.
22
Frequency and wavelength of light
Frequency and wavelength of light
higher energies are associated with shorter wavelengths and lower energies are associated with higher wavelengths
23
Water tank
Light source
Expected way of the light
Effective way of the light
Total reflection at the boundary water-air
Light propagationLight propagation
24
Speed of light in vacuum: C0 = 299’793 km/sec.
Speed of light in glass: Cglass = 200’000 km/sec.
Milan Zurich
1 Millisecond
Milan Zurich1,5 Millisecond
Glas
Vacuum
Speed of lightSpeed of light
25
Wavelength (nm)
covered distance of a wave during one period (oscillation)
Frequency (Hz)
Number of oscillations (period per second)
Wavelength
Frequencyf
t
1 Sek.
Wavelength / FrequencyWavelength / Frequency
26
Frequency and wavelength of light
Frequency and wavelength of lightRelationship between wavelength and
frequency of light
c/
c is the speed of light is the frequency of the light in hertz (Hz)
is the wavelength of the light in meters
wavelength of light in inversely proportional to the frequency
Where:
27
Frequency and wavelength of light
Frequency and wavelength of light
relationship between the energy of a photon and it's frequency
E = h
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
E = hc/
energy of a photon is directly proportional to its frequency and inversely proportional to its wavelength
Where:
28
Frequency and wavelength of light
Frequency and wavelength of light
• 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.
Conclusion Conclusion
29
Nature of lightNature of light
30
Nature of lightNature of light
31
Nature of lightNature of light
32
Nature of lightNature of light
33
Nature of lightNature of light
34
ReflectionReflection
Total reflection
Perpendicularto division line
Division line Light path
Perpendicularto division line
Division lineLight path
Light reflection
35
Total reflection
Border ray
Light refraction
Light source
Optical denser Medium (n1)
Optical thinnerMedium (n2)
Light propagation in glass fiberLight propagation in glass fiber
36
Reflection of lightReflection of light
37
Refraction of lightRefraction of lightRefraction (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.
38
Refraction of lightRefraction of lightRefractive 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
39
Refraction of lightRefraction of lightWhen 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,
40
Refraction of lightRefraction of lightThis 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.
41
Refraction of lightRefraction of lightAnother 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
42
Polarization of lightPolarization of light
43
Diffraction of lightDiffraction of light
44
Difraction of lightDifraction of light
45
Difraction of lightDifraction of light
46
Polarization of lightPolarization of light
47
Polarization of lightPolarization of light
48
Polarization of lightPolarization of light
49
Polarization of lightPolarization of light
50
Brewster’s(Critical) angleBrewster’s(Critical) angle
51
Thank YouThank You