fiber optics pdf

1. Engineering Physics
Paper Code:19EPH131 (Theory)
(ECE, CSE, EEE, EIE & IT Branches)
Dr. K. Chandra Babu Naidu,
Assistant Professor (Physics)
Emp. Id: 700064
GITAM Deemed To Be University,
Bangalore Campus, Karnataka.

2. Syllabus (Theory)
Unit-1: Basics of Electromagentics (9hrs)
Electrostatic Field: Coulombs law and Gauss law, derivation of Coulombs law from
Gauss law, application of Gauss law (line charge, thin sheet of charge and solid
charged sphere), Gauss law of electrostatics in dielectric medium, divergence and
curl of electric fields, electric potential, relation between potential and force ,
Poisson’s and Laplace equations
Magnetostatic Field: Biot-Savart law, divergence and curl of magnetic fields,
continuity equation, Faraday’s and Ampere’s laws in integral and differential form,
continuity equation, Faraday’s and Ampere’s laws in integral and differential form,
displacement current, Maxwell’s equations.
Unit-2: Fiber Optics (7hrs)
Introduction, advantages of optical fibers, principle and structure, acceptance angle,
numerical aperture, modes of propagation, classification of fibers, fiber optic
communication, importance of V-number, fiber optic sensors (Temperature,
displacement and force), applications

3. Unit-3 : Dielectric and Magnetic Materials (10hrs)
Dielectric materials: Introduction, electric polarization, dielectric polarizability,
susceptibility and dielectric constant, types of polarizations( qualitative treatment
only), frequency dependence of polarization, Lorentz(internal) field (quantitative),
Clausius-Mossotti equation
Magnetic materials: Introduction, magnetic dipole moment , magnetization, magnetic
susceptibility and permeability, origin of permanent magnetic moment, classification
of magnetic materials, Weiss theory of ferromagnetism (qualitative), domain theory,
hysteresis, soft and hard magnetic materials
Unit-4:Semiconductor Physics (8hrs)
Introduction, origin of energy band ,intrinsic and extrinsic semiconductors, mechanism
Introduction, origin of energy band ,intrinsic and extrinsic semiconductors, mechanism
of conduction in intrinsic semiconductors, generation and recombination, carrier
concentration in intrinsic semiconductors, variation of intrinsic carrier concentration
with temperature ,n-type and p-type semiconductors, carrier concentration in n-type
and p-type semiconductors.
Unit-5: Semiconductors Devices (8hrs)
Drift and diffusion current in semiconductors, Hall effect and its applications,
magnetoresistance, p-n junction layer formation and V-I characteristics, direct and
indirect band gap semiconductors, construction and working of photodiode, LED, Solar
cell

4. Text Books & Reference Book
Text Books:
1.M.N.Avadhanulu,P.G.Kshirsagar “ A text book of engineering physics, S.chand
publications, 2017
2.S.O.Pillai,Solid State Physics 8th ed., New Age International, 2018
Reference Books:
1.Davis J. Griffiths, “ Introduction to Electrodynamics”-4/e, Pearson Education,2014
2.Gerd Keiser “Optical Fiber Communications” -4/e, Tata Mc Graaw Hill, 2008
3.Chales Kittle “ Introduction to Solid State Physics”, Wiley Publications, 2011
4, S.M.sze “ Semiconductor devices-Physics and Technology” –Wiley, 2008

5. Course Objectives
1. To introduce scientific and mathematical principles that help in understanding
forces fields and waves.
2. To familiarize students with electromagnetic in modern communication systems
3. To impart knowledge concerning the electrical behaviour of dielectric materials
4. To demonstrate the properties of magnets
5. To introduce semiconductor physics and the working of semiconductor devices
6. To acquaint students with semiconductor devices for applications
Course Outcomes
1. Apply the fundamental laws of electricity and magnetism to currents and
propagation of EM waves
2. Identify the mechanisms of polarization in dielectrics and magnetic materials,
conduction in semiconductors and propagation of light in optical fibers
3. Explain the principles of physics in dielectrics, magnetic materials and
semiconductors useful to engineering applications
4. Summarize magnetic hysteresis curve
5. Analyze dielectric loss and carrier concentration in semiconductors
6. Classify solids and calculate conductivity of semiconductors
7. Demonstrate the functioning of solar cell, photodiode and loss mechanisms in
optical fibers

6. Exam Pattern
Three Mid exams ( Best of two Mids will be considered ) - 30M
Class Tests – 5 Class Test - 05M
Assignments -5 - 05M
Total Internals Marks - 40M
Final Semester Exam Total Marks - 60M
Short answers (No Choice) 10x2 - 20M
Essay Answers ( Choice) 5 x8 – 40M
Semester Grading system :
S.No Score (Marks Range %) Result Categories
1. ≥ 90 O
2. ≥ 80 to 89 A+
3. ≥ 70 to 79 A
4. > 60 to 69 B+
5. > 50 to 59 B
6. > 45 to 49 C
7. > 40 to 44 P
8. < 40 F

7. B. Tech., I Year Syllabus
Engineering Physics Laboratory (19EPH131P)
(ECE, CSE, EEE, EIE & IT Branches)
(ECE, CSE, EEE, EIE & IT Branches)

8. Table of Contents
1. List of Experiments
2. Objectives of the Physics lab
3. Instructions to the students
a. Safety Precautions
b. Do’s
c. Don’ts
c. Don’ts
d. Experiment specific
instructions
4. Scheme of evaluation

9. List of Experiments
i.To determine the magnetic field along the axis of a circular coil carrying current.
ii.To determine the numerical aperture of a given optical fiber and hence to find
its acceptance angle
iii.To determine magnetic susceptibility by Gouy’s method
iv.To determine the Hall coefficient using Hall effect experiment
v.To determine the resistivity of semiconductor by Four probe method
vi.To determine the energy gap of a semiconductor.
vi.To determine the energy gap of a semiconductor.
vii.To Study the Characteristics of PN Junction diode.
viii.To study magnetic hysteresis loop (B-H curve).
ix.To determine the dielectric constant of a substance by resonance method.
x.To determine hysteresis loss by CRO.
xi.To Study the Characteristics of Photodiode
xii.To Study the Characteristics of Solar Cell

10. References
•S. Balasubramanian, M.N. Srinivasan “ A Text book of Practical Physics”- S Chand
Publishers, 2017
Learning Outcomes
The students will be able to
•utilize four probe set up and measure resistance (L3)
•determine the susceptibility of a paramagnetic substance (L5)
•understand the characteristics of photodiode, p-n junction diode and solar cell
(L2).
•demonstrate the importance of dielectric material in storage of electric field
•demonstrate the importance of dielectric material in storage of electric field
energy in the capacitors (L2)
•assess the intensity of the magnetic field of circular coil carrying current with
varying distance and able to plot (L5)
•evaluate the acceptance angle of an optical fiber and numerical aperture and loss
(L5).
•determine hysteresis losses by B-H curve and measure magnetic parameters using
hysteresis loop (L5).
•identify the type of semiconductor i.e., n-type or p-type using hall effect (L3)
•determine the band gap of a given semiconductor (L5)

11. Objectives of the Physics lab
 Art of Experimentation: The laboratory provides significant experiences
concerned with the basic laws of physics with the experimental process.
 Experimental and Analysis Skills: The laboratory functions such that a student
develops a broad knowledge of skills and tools of experimental physics and
data analysis.
 Conceptual Learning: The laboratory helps students to become masters in
basic concepts of physics
 Understand and application of Basis of Knowledge in Physics: The lab enables
the student to gain hands-on experience to more clearly understand the
relation between inferences based on theory and the outcomes of
relation between inferences based on theory and the outcomes of
experiments.
 Collaborative Learning Skills: The laboratory enables the student to develop
collaborative learning skills that are crucial to achieving success in many
lifelong endeavors by encouraging them to design innovative project-based
experiments.

12. Instructions to the students
The students must follow the instructions very strictly to experiment
systematically.
It is also to be noted that they need to sufficiently prepare in advance and
recollect the pre-requisite concepts relating to the experiment they are going to
do before coming to the lab.
Questions relevant to the experiment will be asked and marks will be allotted
depending on the performance of the students.
a) Safety Precautions:
1) The first rule is to behave responsibly in the laboratory at all times. Students are
1) The first rule is to behave responsibly in the laboratory at all times. Students are
expected to listen to and follow all instructions given by the laboratory instructor.
This includes all safety precautions and guidelines.
2) When your teacher is showing you lab equipment, listen carefully as some of the
equipment can be dangerous, highly sensitive, and expensive.
3) The students in the physics lab are expected to exercise common sense judgment
when working with the laboratory equipment.
4) Be careful when operating electrical equipment. The lab working surface,
equipment, and your hands should be dry. Check all cords and plugs and make sure
that they are in good condition before using them. Care must be taken when
working with exposed or broken wires and insulation in poor condition.

13. a) Safety Precautions (contd.)
5) It is important to note that all the electrical equipment must be turned off and unplugged
before leaving your workplace.
Always be sure that electrical equipment is in the “turn off" position before plugging the wire
into the socket as well as before removing it from the socket.
Do not grab wires to unplug equipment. Use the plug to disconnect the equipment from the
socket.
6) Use extreme care when handling sharp and sensitive apparatus.
7) When you are working with an open flame or heating materials, never leave them
7) When you are working with an open flame or heating materials, never leave them
unattended.
Hot plates remain hot for several minutes after they are turned off.
Never touch the surface of a hot plate/bulb.
8) The direct or the reflected laser rays should never be pointed into the eyes as this might
cause permanent damage to the eye.
9) Tie back all long hair and remove dangling jewelry during the lab.
10) Wash your hands after each lab experiment.

14. b) Do’s:
1) Teachers expect students to be calm and disciplined. Your behaviour and attitude in
the lab should be excellent. The safety of you and other persons depend on it.
2) There is always plenty to do in the lab, so teachers expect you to arrive on time and
to use your time well.
3) Listen to all instructions given by your teacher and follow them carefully.
4) Read your lab assignments before coming to class. Prepare your pre-lab write-up
before entering the lab.
5) Familiarize yourself with all lab procedures before doing the lab exercise.
6) Get a signature in your observation notebook from your teacher before leaving the
lab.
lab.
7) Perform only those experiments on which you have been instructed.
8) It is your responsibility to take care of lab equipment, use it only as instructed, and
report any damages to your teacher or technician.
9) Clean and dry your lab work area at the close of the lab period. Return all
equipment and materials to the proper place.
10)Use ballpoint pens, not pencils for noting down the observations.
11)Be honest. All procedures and experimental data whether you regard them as
"good" or "bad" at the time should be recorded in the lab notebook.
12)While leaving the lab, Please take your personal stuff with you (like backpacks,
purses, calculators, keys, etc).

15. c) Don’ts
Never attempt to touch the equipment or to do the experiment on your own until your teacher
demonstrates it.
1) Don’t eat or drink in the lab room at any time.
2) Don’t chew gum or eat candy during lab exercises.
3) Don’t be mischievous in the lab.
4) Never remove any pages from the observation notebook and record.
5) Never use electrical equipment around water.
5) Never use electrical equipment around water.
6) Don’t work in the lab alone.
7) Don’t leave the bags and books in the passageways/corridors.
8) Don’t move the laser while it is switched on.
9) Don’t touch the surface of the grating with your fingers.
10) Do not borrow a calculator, scale, pencil, eraser, or any such items from others.
11) Do not move from your allotted working table.
12) Do not consult with others. If you get any doubt, report to the teachers for clarification.

16. d) Experiment based on specific instructions:
-Items to bring in the lab:
All the students are supposed to bring the following items.
 Lab manual
 Logbook or calculator
 Pencil, scale & eraser
 Physics record
 Graph sheets
Call the attendee to your working place to receive any required material,
Call the attendee to your working place to receive any required material,
apparatus, or logarithm tables.
-Before the experiment:
Before you begin to do the experiments write the following particulars in your
record book.
1) Aim
2) Apparatus
3) Formula: with the name of the parameters in it and their units.
4) Draw schematic /circuit diagram of the apparatus using a pencil.
5) Draw a neat tabular form using a pencil and scale.

17. -During the experiment:
Use a pen to enter readings.
At the end of your experiment do the calculations neatly on a
separate page.
-Result: Discuss your result for the probable errors you come across
while experimenting.
The allocation of marks for physics practical is shown below:
Performance in the practical class
Practical examination (sessional)
Viva-voce at the end of the year.

18. 4. Scheme of Evaluation.
a) Internal lab evaluation: 20 Marks
Initial write up, theory, diagrams: 10 marks
 Experiment, result, and Viva:
10 Marks
TOTAL: 20 Marks
(*Average of two internal lab exams will be
taken.)
Conduct of lab and Record: 40 Marks
a) External lab exam:
-Initial write up: 20 marks
 Aim: 2 Mark
 Theory/Circuit
diagram/Apparatus: 13 Marks
 Model observation Table& Model
Graph: 5 Marks
Total = 20Marks
-Experiment, result and Viva: 20
Marks
 Observation, calculation: 10
Coming to the lab with initial preparation:
1 Mark
Discipline in the lab:
1 Mark
Result and Viva:
1 Mark
Completing the record and getting signature:
2 Marks
8 Experiments x 5 Marks = 40Marks
 Observation, calculation: 10
Marks -
 Result: 5
Marks
 Viva-voce: 5
Marks
Total -20Marks
External Lab Exam Total: 40 Marks
GRAND TOTAL = 20+40+40=100
Marks

19. Dr. K. Chandra Babu Naidu,
Assistant Professor (Physics)
Emp. Id: 700064
Unit-II: FIBER OPTICS
Emp. Id: 700064
GITAM Deemed To Be University,
Bangalore Campus, Karnataka.

20. Introduction
Advantages of optical fibers
Principle and structure
Acceptance angle
Numerical aperture
Modes of propagation
Classification of optical fibers
Classification of optical fibers
Fiber optic communication
Importance of V-number
Fiber optic sensors: (a) Temperature sensor
(b) Displacement sensor
(c) Force/pressure sensor
Applications

21. INTRODUCTION OF OPTICAL FIBERS
Optical fiber is a thin and transparent guiding medium
or material which guides the information carrying the light
waves.
Fibers are made up of glass or plastic in cylinder shape.
The inner cylindrical is core of refractive index n1. The
outer is cladding of refractive index n2, such that n1>n2.
Optical signal is transmitted in the fiber on the principle
Optical signal is transmitted in the fiber on the principle
of Total Internal Reflection (TIR).

23. From Snell’s law, n sinθ = n sinθ
Basic principle Total Internal Reflection
Critical Angle Calculation
From Snell’s law, n1sinθ1 = n2sinθ2
For total internal reflection,
θ1= θc and θ2= 90°
n1sinθc = n2 (sin(90°)=1)
θc = sin-¹(n2/n1)
Definition: If the angle of incidence is greater than the
critical angle, the light ray is reflected back to the same
medium. This is called “Total Internal Reflection”.

24. OPTICAL FIBER CONSTRUCTION
Core (Denser medium) – The fiber where light travels.
Cladding (rarer medium) – Surrounds the core
Buffer – Protects fiber from moisture & abrasion
Strength members - To provide toughness and tensile
strength
Outer jacket - Prepared using polyurethane and keeps
all components safe.

25. Angle of Acceptance and Numerical Aperture (NA)
Consider a light ray AO incident at an angle ‘θ0’ enters into the fiber. Let ‘θ1’ be the
angle of refraction for the ray OB. The refracted ray OB incident at a critical angle
(90˚- θ1) at B grazes the interface between core and cladding along BC. If the angle
of incidence is greater than critical angle, it undergoes total internal reflection.
Thus θ0 is called the waveguide acceptance angle and sinθ0 is called the numerical
aperture.
Let n0, n1 and n2 be the refractive indices of the medium, core and cladding
respectively.
From Snell’s law,
From Snell’s law,
nosinθ0 = n1sinθ1 ----------------- (1)

26. At B the angle of incidence is (90 -θ1)
From Snell’s law,
n1sin(90-θ1) = n2sin90
n1cosθ1 = n2
cosθ1 = n2 / n1
1
1
0 sin

n
n
Sin 
From eqn. (1)
1
0
0 sin

n
Sin 
2
1
2
2
0
1
0 1
n
n
n
n
Sin 


The surrounding medium is air, no = 1 2
2
2
1
0 n
n
Sin 


Where sinθ0 is called numerical aperture.

27. N.A
Numerical aperture gives the light gathering capability in
optical fiber.
Therefore for any angle of incidence equal to θi equal to
or less than θ0, the incident ray is able to propagate.
is the condition for propagation.
0
in
Sin 
 S
i 
or less than θ0, the incident ray is able to propagate.
θi < θ0

28. Fractional Index Change Δ:
“It is the ratio of the refractive index difference
between the core and cladding to the refractive index of
the core of an optical fiber”.
Δ =
1
2
1
n
n
n 
Relation between N.A and Δ:
=
1
2
1 n
n
n 


Relation between N.A and Δ:
Consider
Δ =
We have
N.A

29. Considering n1≈n2
Increase in the value of Δ increases N.A
It enhances the light gathering capacity of the fiber. Δ value
cannot be increased very much because it leads to
=
cannot be increased very much because it leads to
intermodal dispersion intern signal distortion
V-number
The number of modes supported for propagation in the
fiber is determined by a parameter called V-number. If
the surrounding medium is air, then
V =

30. Where, ‘d’ is the core diameter, n1 and n2 are refractive
indices of core and cladding respectively, ‘λ’ is the
wavelength of light propagating in the fiber.
V =
If the fiber is surrounded by a medium of refractive index n0,
then,
V =
V =
For V >1, the number of modes supported by the fiber is
given by, number of modes ≈ V2/2.

31. Types of optical fibers (based on manufacturing materials)
1. Glass fibers
 Silica shows refractive index of 1.458 at 850 nm
 These fibers can be formed by mixing the B2O3, GeO2
and P2O5 to silica.
 Examples: Core: GeO2 – SiO2 & Cladding: SiO2
Core: P2O5 – SiO2 & Cladding: SiO2
Core: SiO2 & Cladding: P2O5 – SiO2
Core: SiO2 & Cladding: P2O5 – SiO2
2. Plastic fibers
These fibers are made up of plastic based materials.
Examples: Core: Polystyrene (1.60), Cladding: methyl
methacrylate (1.49)
Core: Polymethyl methacrylate (1.49), Cladding: co-
polymer (1.40)
Benefits: Toughness and durability

32. Modes of Propagation:
Based on refractive index variation
1. Step Index optical fiber
2. Graded Index optical fiber
Based on number of modes of signals
1. Single mode optical fiber
2. Multimode optical fiber
2. Multimode optical fiber

33. Step Index single mode optical fiber: In this optical
fiber the refractive index core remains constant
throughout the core and decreases from step n1 to
n2 at the core cladding interface. In step index
single mode optical fiber only one signal is allowed
to pass through core. The following is the figure
indicating the single mode fiber.

34. Step Index multimode optical fiber: In this optical fiber
the refractive index core remains constant
throughout the core and decreases from step n1 to
n2 at the core cladding interface. In step index multi
mode optical fiber only more than one signal is
allowed to pass through core. The following is the
figure indicating the single mode fiber.

35. Characteristics:
In multimode optical fiber the signal-2/ray -2 reaches the fiber end
earlier than the signal-1/ray-1 due to making smaller angle with the
fiber axis.
 The signals will be overlapped at the out put.
The two signals superpose each other.
Signal follows the triangular path.
 Intermodal dispersion is occurred.
This process is of reflective type.
This process is of reflective type.
The out put information can not be retrieved as it is as provided at
the input.
 Lot of signal loss is observed.
 Number modes through step index fiber: V2/2, V = (2π/λ)*a . NA,
Where λ = wavelength of signal
a = radius of core
NA = Numerical aperture

36. Graded Index multimode optical fiber: In this optical
fiber the refractive index core decreases from fiber
axis to core cladding interface in a parabolic
(sinusoidal) manner. The signal suffers more and
more rarer medium at the interface. Hence the ray
bends away from the interface in the form of
sinusoidal. The following is the figure indicating the
single mode fiber.
single mode fiber.

37. Characteristics:
In multimode optical fiber the signal-1 and signal-2 reach the
fiber end during the same time interval.
 The signals will not be overlapped at the out put.
Signal follows the sinusoidal path.
The two signals will not superpose each other.
 Intermodal dispersion is completely avoided.
This process is of refractive type.
The out put information can be retrieved as it is as provided at
The out put information can be retrieved as it is as provided at
the input.
Signal loss is not observed.
 Number modes through step index fiber: V2/4.

38. Differences between Step index and graded index optical fibers
TASK FOR STUDENTS
Differences between single mode and multi mode optical fibers
Differences between single mode and multi mode optical fibers
TASK FOR STUDENTS

39. Optical fiber communication system:
Parts:
Transmitter
Fiber Repeater
Receiver

40. Fiber Optic Sensors:
General structure for fiber optic sensor
1. Displacement sensor

41. 2. Temperature sensor
Silicon layer absorbs the signal and the intensity of light is varied

42. 3. Force (Pressure) sensor
Once pressure is applied, the bending loss occurs in the fiber.

43. Applications of Optical fibers :
In Communication system:
 Wide band width
Avoiding cross talk
Longer life span
High temperature resistant
Long distance communication system
Light weight and smaller diameter
Light weight and smaller diameter
In Medicine:
Endoscopy
Diagnoses of lungs and stomach
Cancer treatment
Bloodless treatment
Surgeries for joints of legs, bones and knee
In respiratory system
In Sensors: see types of sensors and benefits

44. THANK YOU and ANY QUERIES
THANK YOU and ANY QUERIES