The document discusses optical fibers, detailing their structure, working principles, classification, and applications in communication. It covers the components such as core, cladding, and protective skin, along with phenomena like total internal reflection. Additionally, it highlights the advantages of optical fibers over traditional wiring and their use in various fields, including telecommunications, medicine, and military.

2.  INTRODUCTION
 WHAT ARE OPTICAL FIBERS
 STRUCTURE OF OPTICAL FIBER
 WORKING PRINCIPLE OF OPTICAL FIBER
 CLASSIFICATION OF OPTICAL FIBER
 OPTICAL FIBER IN COMMUNICATION
 APPLYCATIONS OF OPTICAL FIBER
 CONCLUSION

3.  Fiber optics deals with the transformation of
information by light through fibers.
 Fiber is made up of glass , plastic or other
transparent materials.
 Light beam acting as a carrier wave is capable
of carrying more information then radio and
microwave.
 In 1870 , John dyndall observed that the
propagation of light through optical fiber.
 A single fiber can carry 140 mega byte of
information up to 220 km in one second.

5.  CORE : Central tube of very thin size made up
of optically transparent dielectric medium and
carries the light transmitter to receiver . The
core diameter can very about 5 um to 100um.
 CLADDING : Outer optical material
surrounding the core refractive index lower
than the core. It helps to keep the light within
the core throughout the phenomena of total
internal reflection.
 PLASTIC COVERING (OR) PROTECTIVE
SKIN : Plastic coating that protects the fiber
made of silicon or rubber.

6.  TOTAL INTERNAL REFLECTION
 When a ray of light travels from a denser
medium to a rarer medium such that the angle
of incidence is greater then the critical angle ,
the ray reflects back into the same medium this
phenomena is known as “ total internal
reflection”.
 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 the fiber is
bent.

8.  On the basis of number of modes of
propagation the optical fiber are classified into
two types :
 (I) Single mode fiber (SMF)
 (II) Multi mode fiber (MMF)

9.  In the single mode fiber only one mode is
propagated that type of fiber is called “ single
mode fiber”
 In the single mode optical fiber the core as a
diameter of 8-12 um and cladding as a diameter
of 125um.

10.  In the multimode fiber, fiber carriers many
hundreds of modes that type of fiber is called
as the “ multimode optical fiber”
 In the multimode fiber the core as a diameter
50 – 200 um and cladding as a diameter of 125 –
400nm.
 In the multimode fiber the light can travel in
many different paths through the core of the
fiber and can enter & live the fiber at various
angles.

12. Based on the refractive index
 Based on the variation of refractive index of
core of optical fiber . The fiber are classified
into two types .
 (I) Step index optical fiber
 (II) Graded index optical fiber

13.  In the step index optical fiber , the refractive index
of the core remains constant throughout the core
and decrease the step n1 to n2 at the cladding
interface.
 Thus , it is known as “step - index optical fiber”
 The transformation of information is in the form of
pulse (or) signals.
 Depending upon their refractive index profiles
step index fiber are characterized of two types they
are
 (I) Step index single mode fiber
 (II) Step index multimode fiber

14.  A step index single mode fiber , a single light
ray form the signal enters into the fiber and
transverses a single path and forms the output
signal.

15.  In step index multimode fiber , due to large of
core , greater no.of rays from the input singles
enters into the core and takes multi paths.
 Within the fiber axis suffers more reflections
through the fiber and takes more time to
transverse the optical fiber less no.of reflections
and with in a short time.
 It transverses the optical fiber , and the o/p end
we receive the ray(2) first and later we get ray(1).
 Due to path differences between the two light rays,
they superimpose to form the output signal.

16.  The signals are overlapped .
 In this we get signal distortion known as “inter
model dispersion”.
 It is difficult to retrieve the information carried
by the distorted output signal.

17.  In a graded index optical fiber, the core
refractive index varies continuously , that
means the refractive index of the core decreases
from the fiber axis to the classing interface in a
“parabolic” manner.

18.  The fundamental digital fiber communication
system is shown in figure.

19.  In the life of fiber is longer than copper wire
 Handling and installation costs of optical fiber
is very nominal
 It is unaffected with electromagnetic
interference.
 There is no necessity of additional equipment
for protecting against grounding and voltage
problems .

20.  Highly skilled staff would be required for
maintenance.
 Precise and costly instruments would be
required
 Costly under utilized.
 Jointing of fiber and splicing is also time
consuming.

21.  Optical fiber have wider range of applications
in almost all fields , some are been specified
below
 In telecommunication field
 In space applications
 Broadband applications
 computer applications industrial applications
 Mining applications
 In medical applications
 In military applications etc..