Optical Fiber Introduction

1. Prof. Junaid Mandviwala
Department of Electronics and
Telecommunication
Rizvi College of Engineering
Optical Communication

2. Scheme

3. Prerequisites
 Physics
 Electromagnetic Wave Propagation
 Electronic Devices and Circuits
 Principles of Communication

4. Course Outcome
After successful completion of the course student
will be able to
 List, write and explain fundamentals and
transmission characteristics of optical fiber
communication.
 List, write and explain principles and
characteristics of various sources, detectors
and various fiber optic components.
 Calculate parameters for optical link budgeting
and analyze the link.

5. Syllabus
1. Optical Fiber & Their Properties
2. Transmission Characteristics of Optical Fiber
3. Optical Sources
4. Optical Detectors
5. Fiber Optic Components
6. Optical Link

6. Books
Text Books
 Optical Fiber Communication – Gerd Keiser, 4th Ed.,
MGH, 2008.
 Optical Fiber Communications– – John M. Senior,
Pearson Education. 3rd Impression, 2007.
Reference Books
 Fiber Optics Communications-Harold Kolimbiris
 Introduction to Optical Fibers, Cheri, McGraw Hill.
 Fiber optic communication– Joseph C Palais: 4th Edition,
Pearson Education.

7. Examination Scheme

8. Chapter 1 : Optical Fiber and Their
Properties

9. History

10.  Fiber optics deals with study of propagation of light through transparent
dielectric waveguides. The fiber optics are used for transmission of data from
point to point location. Fiber optic systems currently used most extensively as
the transmission line between terrestrial hardwired systems.
 The carrier frequencies used in conventional systems had the limitations in
handling the volume and rate of the data transmission. The greater the carrier
frequency larger the available bandwidth and information carrying capacity
Historical Development

11.  First Generation
The first generation of light wave systems use GaAs semiconductor Laser and
operating region was near 0.8µm. Other specifications of this generation are as :
 Bit Rate: 45Mb/s
 Repeater Spacing: 10 Km
 Second Generation
 Bit Rate: 100Mb/s to 1.7 Gb/s
 Repeater Spacing: 50 km
 Operation Wavelength: 1.3 µm
 Semiconductor: In GaAsP

12.  Third Generation
 Bit Rate: 10 Gb/s
 Repeater Spacing: 100 km
 Operation Wavelength: 1.55 µm
 Fourth Generation
 It uses WDM technique
 Bit Rate: 10 Tb/s
 Repeater Spacing: >10000 km
 Operation Wavelength: 1.45 to 1.62 µm
 Fifth Generation
 It uses Roman amplification technique and optical solitiors.
 Bit Rate: 40 – 160 Tb/s
 Repeater Spacing: 24000 km – 35000km
 Operation Wavelength: 1.53 to 1.57 µm

13. Electromagnetic Spectrum

14. General System

15. Advantages
 Large Transmission bandwidth
 Small Size and Light in Weight
 Low Transmission loss
 Electrical Isolation
 High Degree of Signal Security
 No Crosstalk and Immunity to Interference
 Low Cost
 Reliable System

16. Large Transmission Bandwidth
 Light rays are used as the carrier waves which has
very high frequency therefore bandwidth increases.
 It has potential bandwidth of around 10^14 hertz.

17. Small Size and Light Weight
 The Diameter of optical fiber is very small (slightly more than the
human hair)
 Optical fibers occupy less space.

18. Low Transmission Losses
 Total Internal Reflection phenomenon
takes place in optical fiber which offers
very low losses
 Large spacing between the repeaters
is possible due this low losses
 Optical fibers can be used for long
distance communication because the
transmission losses are very low (0.2
dB/Km)

19. Electrical Isolation
 Optical fibers are made of Glass (Silica) or Plastic,
These are nothing but insulators.
 So the light rays travel inside the insulating material
 Therefore there is no chance of Electric Shock, Short
Circuit or sparking hazards etc.

20. High Degree of Signal Security
 Light rays propagates inside the core of the Optical Fibers
 Hacking of the signal is not possible
 If someone tries to steal the signals, then it can be easily detected
 This feature of the optical fibers is useful especially for military,
banking and sending secrete messages.

21. No Crosstalk and Immunity to Interference
 In optical fibers, there is no interference in electrically noisy
environment.
 There is no effect of EMI and RFI
 Fibers can be cabled together without any crosstalk

22. Low Cost
 Optical fibers are made of Glass (silica or sand) or plastic,
available in plenty therefore the cost of optical fibers are very low
 Repeaters and other electronic equipment’s are required in less
amount.

23. Reliable System
 Repeaters and other electronic equipment’s are required in less
amount which makes it more reliable.
 Optical fibers can easily serve for 20- 30 years
 High reliability reduces the maintenance and maintenance cost.

24. Comparison between optical fiber communication &
Conventional communication systems
Optical Fiber Communication System Conventional Communication System
1. Requires a bandwidth of 1013 to 1016 Hz. 1.Requires a bandwidth of 500 MHz
2 .Light weight. 2. Heavier in weight.
3. Immune to R.F. interference. 3. Needs external shielding.
4. Electrical isolation. 4. Exhibits earthing problems.
5. Low loss of about 0.2 dB/km. 5. Loss of about 10dB/km.
6. Secure signal propagation. 6. Signal can be tapped easily.
7.Due to increased bandwidth higher data
rates
7. Low data rates compared to optical
fiber.

25. Compare the Optical Communication System with Microwave system
Optical Communication System Microwave System
1. Uses glass optical fibers or plastic optical fibers
for transmission.
1. Uses co-axial cable or microwave waveguides for
transmission.
2. Low weight, hence large transmission distance
or same weight of microwave link.
2. Heavier than optical fibers.
3. Large bandwidth of range 1013 to l016Hz. 3. Bandwidth is lesser in the range of 108 to 1010Hz.
4. Electrically isolated, hence no shielding
is required.
4. Prone to electrical disturbances and hence, shielding
for reducing RE interference.
5. Low loss of 0.2dB/km. 5. A considerable loss of 5 dB/km.
6. Large spacing between repeaters about 1 in 300
km.
6. Spacing distance between repeaters is less, is
suitable only for short distance if waveguides are used.

26. 7. Because large bandwidth, higher data rate of the
order of terabits per second.
7. Data rates of mega bits per second can be
obtained.
8. Message security is obtained. 8. Signal can be tapped easily.
9. No cross talk, hence many fiber
communication channels can be packed
inside one single cable.
9. If shielding is not done properly, cross talk is
introduced.
10. Expensive transmitter and receiver. 10. Simple and less expensive transmitter and
receiver.
11. Difficult coupling. 11. Easy coupling.
12. Power transmission depends upon the
quantum efficiency of light source (LED or
LASER)
12. Output power is directly coupled to the
transmission line.
13. Unable to excite the terminal device
directly.
13. Able to operate the terminal device directly.