This document provides an overview of optical fibers and optical fiber communication systems. It begins with an introduction and outline then discusses the structure, working principle, classification, and components of an optical fiber communication system. Key points covered include the total internal reflection that allows fibers to act as waveguides, the core and cladding structure, single mode vs multimode fibers, and applications such as endoscopy. The document concludes that while optical fiber communication has some disadvantages, it has revolutionized telecommunications due to features like immense bandwidth, low loss transmission, and electrical isolation.

1. Presented by –
Ram Singh Patel
Roll no.-CSJMA13001390104
ECE (4rd year),UIET, Kanpur
Submitted to:-
Er. Somesh Malhotra
Er. Atul Agnihotri
(Summer Training In-charge)

2. Brief flow of presentation
 Introduction
 What are Optical Fibers ?
 Structure of optical fiber
 Working principle of optical fiber
 Optical fiber communication system
 Advantage / Disadvantage of optical fiber
 Application of optical fiber
 Conclusion

3. What is Optical Fiber ?
 An optical fiber is a hair thin cylindrical fiber of glass or
any transparent dielectric medium.
 The fiber which are used for optical
communication are wave guides
made of transparent dielectrics.
 Its function is to guide visible and
infrared light over long distance.

4. Structure of optical fiber

5. Conti…
 Core- central tube of very thin size made up of
optically transparent dielectric medium and carries
the light form transmitter to receiver. The core
diameter can vary from about 5um-100 um.
 Cladding- outer optical material surrounding the core
having reflecting index lower than core. It helps to
keep the light within the core throughout the
phenomena of total internal reflection.
 Buffer Coating- plastic coating that protects the fiber
made of silicon rubber. The typical diameter of fiber
after coating is 250-300um.

6. Working principle
 Total Internal Reflection(TIR)
 When an ray of light travels from a denser to a rarer medium such that
the angle of incidence is greater than the critical angle, the ray reflects
back into the same medium this phenomena is called TIR.
 In the optical fiber the rays undergo repeated total number of
reflections until it emerges out of the other end of the fiber, even if
fiber is bend.

7. Classification of optical fiber
 Optical fiber is classified into two categories based
on:-
1) The number of modes-
 Single mode fiber(SMF) and
 Multi-mode fiber(MMF)
2) The reflective index-
 Step index optical fiber
 Graded- index optical fiber

8. On basis of number of modes:-
Single mode fiber-
 In single mode fiber only one mode can propagate through the
fiber.
 It has small core diameter (5um) and high cladding diameter
(70um).
 Difference between the refractive index of core and cladding is
very small.
 There is neither dispersion nor degradation therefore it is suitable
for long distance communication.
 The light is passed through the single mode fiber through laser
diode.

9. Multi- mode fiber
It allows a large number of modes for
light ray travelling through it.
The core diameter is 40um and that
of cladding is 70um.
The relative refractive index
difference is also large than single
mode fiber.
There is signal degradation due to
multimode dispersion.
It is not suitable for long distance
communication due to large
dispersion and attenuation of signal.

10. On the basis of refractive index
 There are two type of optical fiber:-
1) Step index optical fiber
2) Graded- index optical fiber

11. Single Index fiber:-
Step-index optical fiber-the refractive index of core and
cladding are constant.
The light ray propagate through it in the form of
meridiognal rays which cross the fiber axis during every
reflection at the core cladding boundary.
Graded Index Fiber:-
In this type of fiber core has a non uniform refractive index
that gradually decrease from the center towards the core
cladding interface.
The cladding has a uniform refractive index.
The light rays propagate through it in the form of helical
rays. They never cross the fiber axis.

12. Optical Fiber Communication
System
 Information source- it provide an electrical signal to a
transmitter comprising an electrical stage.
 Electrical transmitter- It drives an optical source to give an
modulation of the light wave carrier.
 Optical source- It provides the electrical-optical
conversion. It may be a semiconductor laser or an LED.

13. Continue..
Optical cable- It serve as transmission medium.
Optical detector- It is responsible for optical to electrical
conversion of data. It may be a photodiodes, phototransistors or
photoconductors.
Electrical receiver: It is used for electrical interfacing at the
receiver end of the optical link and to perform the signal
processing electrically.
Destination: It is the final point at which we receive the
information in the form of electrical signal.

14. Attenuation
Attenuation is the loss of the optical power.
Attenuation in optical fiber take place due to elements like
coupler, splices, connector and fiber itself.

15. Variation of specific attenuation
with wavelength

16. Advantage of Optical Fiber
 Immense bandwidth to utilize
 Total electrical isolation in the transmission medium
 Very low transmission loss
 Small size and light weight
 High signal security
 Very low power consumption and wide scope of
system expansion etc.

17. Disadvantage
1) System installation is very costly.
2) Only point-to-point communication is possible.
3) Precise and costly instruments would be required.
4) Splicing is time consuming.
5) It accept only unipolar codes.

19. Applications
 Optical fiber have wider range of
application in almost all field,
some are specified below:-
 In telecommunication field
 Civil, consumer and industrial
application
 In military applications
 Broadband applications
 In decorations, etc.

20. The Endoscope(In medical field)
There are two optical fibers in endoscope:
1) One for light, to illuminate the inside of patient.
2) Another for a camera to send the images back to
doctor.

21. Conclusion
At the last, there are some negatives of using
optical fiber communication system in terms of
splicing, coupling, set up expenses etc. but it is an un
avoidable fact that optical fiber has revolutionized the
field of communication. As soon as computers will be
capable of processing optical signals, the total arena of
communication will be opticalized immediately.

22. Thank you…..