1. Optical Communication system
CHAPTER 1
Optical
Communication system
School of Computer and Communication Engineering,
University Malaysia Perlis (UniMAP)
EKT 465

2. Coursework Contribution
COURSE IMPLEMENTATIONS
Lecture
3 hours per week for 14 weeks (Total = 42 hours)
Tutorial +assignment
20%
Test 1&2
20 %
Final Exam
60%
Total
100%
Lecturer: Dr. Hilal A. Fadhil,
Prof. Dr. Syed Alwee Aljunid (hp: )

3. Course material Course text book: Reference Books:
“Gerd Keiser, Optical Fiber Communications, 3rd Edition, Mc Graw Hill, 2000
Reference Books:
Joseph C. Palais, Fiber Optic Communications, 5th Edition, Prentice Hall, 2005
Jeff Hecht, Undestanding Fiber Optics, 5th Edition, Prentice Hall, 2006

4. 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

5. 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 ”?

7. A History of Fiber Optic Technology
The Nineteenth Century
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

8. The Twentieth Century core cladding
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
cladding
core

9. 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

10. Optical Wavelength Bands
Short
band
C-band: Conventional Band
L-band: Long Band

11. 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

12. Applications of Fiber Optics
Military
Computer
Medical/Optometric
Sensor
Communication

13. Military Application

14. Computer Application

15. Sensors Gas sensors Chemical sensors Mechanical sensors Fuel sensors
Distance sensors
Pressure sensors
Fluid level sensors
Gyro sensors

16. Medical Application
Endoscope
Eyes surgery
Blood pressure meter

17. 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 using (Li-Fi Technology).

18. Li-Fi Technology

19. Real time usage of Li-Fi
Li-Fi advantages: High Speed, Green Information Technology, Lighting points used as Hotspot

20. Fiber Optic Fundamentals

21. Advantages of Fiber Optics
Immunity from Electromagnetic (EM) Radiation and Lightning
Lighter Weight
Higher Bandwidth
Better Signal Quality
Lower Cost
Easily Upgraded
Ease of Installation
The main advantages:
Large BW and Low loss

22. Immunity from EM radiation and Lightning:
- 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.

23. 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.

24. Lower Cost 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.

25. Principles of Fiber Optic Transmission
Electronic signals converted to light
Light refers to more than the visible portion of the electromagnetic (EM) spectrum

26. 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.
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.

28. 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.

29. 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

30. Fiber optic links contain three basic elements
Elements of an Optical Fiber communication
Fiber optic links contain three basic elements
transmitter
optical fiber
receiver
Optical Fiber
User
Input(s)
Transmitter
Receiver
User
Output(s)
Optical-to-Electrical
Conversion
Electrical-to-Optical
Conversion

31. Transmitter (TX) Electrical Interface Data Encoder/ Modulator Light
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

32. Receiver (RX) Light Detector/ Amplifier Data Decoder/ Demodulator
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
User
Output(s)
Optical
Input
Light Detector/
Amplifier
Data Decoder/
Demodulator
Electrical
Interface

33. 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

34. Fiber Optic Components

35. 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)

36. A FIBER STRUCTURE

37. Light Emitters 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

38. Detectors 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

39. 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

40. Exercises (page no.25/ Text book)
Q1: Convert the following absolute power levels to dBm values: 1pW, 1nW, 1mW.
Q2: What are the advantages of using Optical fiber over other wireless communication system ? Give an example to show the application of fiber optics in the real life.
Q3: A 50-km long optical fiber has a total attenuation of 24 dB. If 500 micro watt of optical power get lanuched into the fiber, what is the output power level in dBm and in Mico watt?
Q4: There are many methods which have been used to fabricate and manufacture an optical fiber, list out at least three methods and explain one of them.
Q5: Convert the following dBm values to power level in mW: -13 dBm, -6 dBm.
Q6: Discuss and sketch the block diagram of an optical fiber communication elements?