This course about Optical Fiber : Topic : 1.Overview of communication medias. 2.Refraction&reflection of light. 3. Fiber optic communication system. 4.Optical fiber source & detector. 5.Definition & type of F.O. 6.Fiber optic structure. 7.Installation of F.O.C. 8.Optical fiber connections. 9.Definition & types of attenuation. 10. Measurement methods. 11. Attachment photos. 12. Practical parts(O&M,splicing, testing……etc.

1. FIBER OPTIC CABLE COURSE
1.Overview of communication medias.
2.Refraction&reflection of light.
3. Fiber optic communication system.
4.Optical fiber source & detector.
5.Definition & type of F.O.
6.Fiber optic structure.
7.Installation of F.O.C.
8.Optical fiber connections.
9.Definition & types of attenuation.
10. Measurement methods.
11. Attachment photos.
12. Practical parts(O&M,splicing, testing……etc.

2. FIBER OPTIC CABLE COURSE
– Over view of communication medias:-
• Introduction:-
• There are four types of media that can be used in
transmitting information in telecommunications
system, which are:
1. Copper wire
2. Coaxial cable (actually an adaptation of copper wire)
3. Wireless
4. Fiber optic

3. Disadvantages of Copper cable
• Too expensive with respect to fiber optic cable.
• need many pipes to be installed for pulling in the
cable.
• Always exposed to be theft due to its high
commercial price.
• Need to install in short distances as a
communication system.
• Low carrying capacity (small bandwidth).
• Can be affected with interference , crosstalk & other
neighboring circuit (as happened in wireless medias).

4. Advantages of fiber optic cables:
• SPEED: Fiber optic networks operate at high
speeds - up into the gigabits.
• BANDWIDTH: large carrying capacity.
• DISTANCE: Signals can be transmitted further .
• RESISTANCE: Greater resistance to electromagnetic
noise such as radios, motors or other nearby cables.
• Small size & weight(many KM’s can be delivered)
• MAINTENANCE: Fiber optic cables costs much less to
maintain.

5. Refraction & reflection of light
• As a light ray passes from one transparent medium to
another, it changes direction; this phenomenon is called
refraction of light.
• How much that light ray changes its direction depends on
the refractive index of the mediums.

6. Total internal reflection:
Light pulses move easily down the fiber-optic line because of a principle known as total internal
reflection. "This principle of total internal reflection states that when the angle of incidence
exceeds a critical value, light cannot get out of the glass; instead, the light bounces back in.
When this principle is applied to the construction of the fiber-optic strand, it is possible to
transmit information down fiber lines in the form of light pulses.

7. Refractive index (n) of the medium: -
This can be define as, is the ratio of the speed of light in vacuum (air) (Cn=1) to the
speed of light in the medium) (e.g. glass, for the glass n=1.5).
n=C/V
WHERE: C= is the velocity of light in the vacuum, which is constant(300000 km/s).
V= is the velocity of light in glass, which depends on the density of the glass.
Snells law:
C1/C2= n2/n1
C1= first medium( AIR), C2 = second medium GLASS).
n2=second medium(1.5), n1= first medium(1).THERE FOR C for the glass is:
Cg= 300000 km/s X 1/ 1.5=200000 km/s.
Also there is basic relation between C , f & λ which is:
C= f x λ.
WHERE : C= is the speed of propagation.
f= frequency.
λ = wave length. (windows wavelengths for the for the light in fiber optic
which is in the range of 800 nm – 1700 nm).

8. Refraction Index
• The index of refraction (n) is the ratio of the speed of
light in a vacuum (c) to its velocity in a material (v)
– n = c / v
• Light changes speed (and bends) as it passes through
different mediums
Material Index (n) Light speed (km/s)
Vacuum 1.0 300 000
Water 1.33 225 000
Glass 1.5 200 000
Diamond 2.0 150 000

9. Frequency Hz
1800 1600 1400 1200 1000 800 600 400 200
2x1014 3x1014
5x1014
1x1015
Infrared
range
Ultraviolet
range
wavelength nm
Visible
range
single mode Laser
multi mode Laser
Laser
range
Radar
range
Wavelength range of optical
transmission

10. Fiber optic communication system:
• Fiber-optic communication is a method of transmitting information from one
place to another by sending pulses of light through an optical fiber. The light
forms an electromagnetic carrier wave that is modulated to carry information.
First developed in the 1970s, fiber-optic communication systems have
revolutionized the telecommunications industry and have played a major role in
the advent of the Information Age. Because of its advantages over electrical
transmission, optical fibers have largely replaced copper wire communications in
core networks in the developed world.
The process of communicating using fiber-optics involves the following basic
steps: Creating the optical signal involving the use of a transmitter, relaying the
signal along the fiber, ensuring that the signal does not become too distorted or
weak, receiving the optical signal, and converting it into an electrical signal.

11. Optical communication system

12. Optical source and detectors: -
• (1) Optical source:
• Optical sources (transmitters) are an electronic components used to
convert the electrical signal to optical signal and send it through optical
fibers after certain modulation to the signal. The most optical sources
used in modern fiber optic system are laser diode (LD) and light emitting
diode (LED), the advantages of these two diode are so small and more
suitable for simple electronic energy.
• But generally we use light emitting diode for short distances and laser
diode long distances. The word LASER stands for, Light Amplification by
Stimulated Emission Radiation.
• The LDs and LEDs are operated infrared portion of electromagnetic
spectrum, so their light out put usually invisible to the human being eye.
Their operating wavelengths are chosen to be compatible with the
lowest transmission loss and high sensitivity ranges of photodiodes.
These wavelengths are 850 nm, 1310 nm and 1550 nm.

13. (2)Optical detectors:-
• The optical detectors (receivers) convert the optical
signal back into original electrical signal.
• The detector of the optical signal is either PIN-type
photo diode or avalanche type photo diode. The
photo diode demodulates an optical signal by
generating a current proportional to the intensity
of electrical signal.
• For the area of operation in fiber optic
transmission system where long distances
transmission (greater than 100km), we use
avalanche photo diode because it is designed for
applications requiring greater sensitivity.

14. •Definition of O.F: -
Physically optical fiber is a very thin flexible medium having solid cylindrical
waveguide consisting of three layers, which are:
1. The core.
2. The cladding.
3. The coating or jacket.
Types of F.O.:-
There are three types of fiber optic commonly used: single
mode, multimode and plastic optical fiber (POF).
Transparent glass or plastic fibers which allow light to be guided from
one end to the other with minimal loss.

15. Types of fiber optic:
• Single Mode cable is a single stand of glass fiber with
a diameter of 8.3 to 10 microns that has one mode of
transmission. Single Mode Fiber with a relatively
narrow diameter, through which only one mode will
propagate typically 1310 or 1550nm. Carries higher
bandwidth than multimode fiber, but requires a light
source with a narrow spectral width. Also single mode
can be called as mono-mode optical fiber, single-
mode fiber, single-mode optical waveguide, uni-mode
fiber. Has a cladding diameter of 125 microns &
coating or jacket diameter of 250 microns.

16. Single mode fiber:
• Means only one single united beam running or
passing through the core and taking the
center of it from first to end.
• Used for long distance applications(according
to Tx equipment type).

17. • Multimode cable is made of of glass fibers, with a common
diameters in the 50-to-100 micron range for the light carry
component (the most common size is 62.5). POF is a newer
plastic-based cable which promises performance similar to
glass cable on very short runs, but at a lower cost.
Multimode fiber gives you high bandwidth at high speeds over
medium distances. Light waves are dispersed into numerous
paths, or modes, as they travel through the cable's core typically
850 or 1300nm. Typical multimode fiber core diameters are 50,
62.5, and 100 micrometers. However, in long cable runs (greater
than 3000 feet [914.4 meters), multiple paths of light can cause
signal distortion at the receiving end, resulting in an unclear and
incomplete data transmission.

18. 1. STEP-INDEX MULTIMODE FIBER has a large core, up to 100
microns in diameter. As a result, some of the light rays that
make up the digital pulse may travel a direct route, whereas
others zigzag as they bounce off the cladding. These
alternative pathways cause the different groupings of light
rays, referred to as modes, to arrive separately at a receiving
point. The pulse, an aggregate of different modes, begins to
spread out, losing its well-defined shape. The need to leave
spacing between pulses to prevent overlapping limits
bandwidth that is, the amount of information that can be
sent. Consequently, this type of fiber is best suited for
transmission over short distances, in an endoscope, for
instance.

19. 2. GRADED-INDEX MULTIMODE FIBER contains a core in which the
refractive index diminishes gradually from the center axis out
toward the cladding. The higher refractive index at the center
makes the light rays moving down the axis advance more slowly
than those near the cladding. Also, rather than zigzagging off the
cladding, light in the core curves helically because of the graded
index, reducing its travel distance. The shortened path and the
higher speed allow light at the periphery to arrive at a receiver
at about the same time as the slow but straight rays in the core
axis. The result: a digital pulse suffers less dispersion.

20. Fiber cable structure
• Definitions:
• Cabling is the process of packaging optical fibers in a solid
tube (called sheath) for ease of working activities ,handling &
protection.
• From point of usage ,fiber cable had been classified in two
categories, one for external plant covered with the sheath
called polythene(PE) & other for internal installation covered
with flexible sheath called polyvinyl chloride (PVC).
• Also according to the type of the fiber, the cable can be
classified to single & multi mode cable.

21. Fiber cable manufacturing:
• Fiber cable normally manufacturing in
different style structure:
1. One called maxi-tube cable, in which all
fibers were inserted inside one tube situated
in the middle of the cable.
2. Another type called loose buffered tube
cable , in which all fibers were divided in to
many colored tubes in the cable, situated in
circular shape , in addition to another
elements called fillers to keep the circularity
shape of the cable.

22. Maxi-tube cable
P.E sheath
corrugated
sheath
Jelly filling
compound
Ripcord
fibers
Maxi-tube

23. Buffer tube cable

24. Samples of fiber cables
• Direct buried cable • Submarine cable

25. Installation of optical fiber cables:-
• The fiber optic cables installed in a pipe called
conduit system for more protection and ease of
maintenance. There is pulling tool used to
withdraw the cable in the conduit system, also
there are manholes and hand holes used to ease
the pulling of the cable and storing the connection
point of the cable. Some times outside plant cable
are directly laid in the ground after digging deep in
the ground and back filling again, and this can
decrease the cost of the installation.

26. Installation methods
• Installation methods for both copper
cables and optical fiber cables are similar.
• Fiber cable can be pulled with much
greater force than copper wire if pulled
correctly.
• Long distances laying mean cables are
spliced together, since cables are not
longer than about 4 km.
• Most splices are by fusion splicing.

27. Do not pull on the fibers
• Pull on the strength members only! Any other
method may put stress on the fibers and harm
them.
• Most cables cannot be pulled by the jacket.
• Do not pull on the jacket unless it is specifically
approved by the cable manufacturers and you
use an approved cable grip.

28. Do not exceed the cable bend radius.
• Fiber is stronger than steel when pulled
straight, but it breaks easily when bent too
tightly.
• These will harm the fibers, maybe
immediately, maybe not for a few years,
but they may be harmed and the cable
must be removed and thrown away!

29. Conduit and Inner-duct.
• Outside plant cables are either installed in conduit or inner-duct or
direct buried, depending on the cable type.
• Building cables can be installed directly, but can be put inside
plenum-rated inner-duct.
• This inner-duct will provide a good way to identify fiber optic cable
and protect it from damage, generally a result of someone cutting it
by mistake!
• The inner-duct can speed installation and maybe even cut costs.
• It can be installed quickly by unskilled labor, then the fiber cable can
be pulled through in seconds. An inner-duct may have a pulling tape
already installed.

30. Optical fibers connections:-
Definition:
• The purpose of fiber termination is to provide easy ways for fiber cross
connection and light wave signal distribution. There are two types of
fiber terminations: connectors and splicing.
• Splicing:
• Splicing is the process of connecting two bare fibers directly without
any connectors. There are two methods of fiber optic
splicing: mechanical splicing
and fusion splicing.
Fusion splicing techniques:-
This type of connection is done by a certain machine called fusion splicer ,
this splicer is the microprocessor machine used to produce a fixed low loss
connection between the two fibers. This splicing is done, in the manner as
heating, melting and then two fiber fused together. When the two fibers are
totally fused, the machine displays a certain value of attenuation for this
fused point. This fusion process is shown in the figure below:-

31. fusion splicer

32. Fiber end mismatches

33. • Mechanical connections: - In this type the two fibers are
mechanically connected together, this can be done by two
methods:
1. Sleeves method: In this method the two fibers coatings are
stripped out of the fiber and cleared with ALCOHOL and then
cleaved (cut) with certain cleaving lengths, and then the two
end of the fiber are inserted in one sleeve and then pressed
with the certain tool.
2. Connector method: The two fibers are already prepared in
screw connector or any other form and then approached
together in female connector and then tightly closed.
• Closures:-
• Are solid tubes or containers used to protect the fibers at the
point of connection of two cables, manufactured from solid
plastic material.

34. Definition & causes of attenuation
• is the decrease (loss) in magnitude of the signal power in
transmission between points.
• Attenuation usually measured in decibel (dB) at specific
wavelength.
• As light is guided through the core of a fiber, four properties can
cause attenuation:
1.Absorption:
• Occurs when light strikes impurities in core glass and is
absorbed.
2.Scattering:
• Occurs when light strikes an area where the material density
changes.
3.Macrobending:
• Is large scale bending of the fiber bend which exceeds the fiber
bend radius and causes light to leave the core and travel in the
cladding (usually an installation problem).
4.Micro bending: Is
microscopic distortion of the fiber, which causes light to leave
the core and travel in the cladding (created during
manufacturing).

35. • Link loss (dB) = Cable loss + Connectors loss +
Splices loss.
• Cable loss (dB) = Cable length (km) x Loss coefficient
(dB/km)*
• Connector loss (dB) = number of connector pairs x
connector loss (dB)*
• Splice loss = number of splices x splice loss (dB)*.
• Accepted attenuation range:
• At 1310 nm should be in the range of 0.30 dB/km to 0.35
dB /km.
• At 1550nm , should be in the range of 0.20 dB /km to
0.25 dB /km.
Acceptable link loss calculation

36. Measurements methods:
1. transmission method:
• The simplest and most accurate method of
measuring the end-to-end loss of an optical
fiber is done by light source and power meter.
Shown here above is the proper method for
storing reference and then measuring loss.
• Multimode and single mode optical
measurements can be done perfectly by this
method .

37. Link Loss measurements

38. 2.Back scattering method
LCD
• The optical time domain reflectometer (OTDR),
sends out a pulse of light and measures the level of
light that is reflected back. An optical coupler
allows both optical source and optical receiver to
be connected to the same fiber.
CONTROLLER
LASER SOURCE
DETECTOR
Coupler/
splitter
Fiber under test

39. Pulse width

40. O.T.D.R
– TYPICAL BACKSCATTERED TRACE
Fusion spliceConnector
Fibre
end
O.T.D.R
Att(dB)
Dist (Km )
O.T.D.R
connector
Noise
Rayleigh
scattering
Fresnel
reflection
Mechanical
splice

41. Visual fault locator
• A "visual fault locator". It injects a bright red laser
light into the fiber to find faults. If there is a high
loss, such as a bad splice, connector or tight bend
stressing the fiber, the light lost may be visible to
the naked eye. This will find events close to the
OTDR or close to another event that are not
resolvable to the OTDR. It's limitation is distance
too, it only works over a range of about 2.5 miles
or 4 km.
• The visual fault locator is so valuable a tool that
many OTDRs now have one built into them.

42. Attenuation & Dispersion
Input pulse

Output pulse
 Attenuation () : the signal received is less than the transmitted.
 Modal dispersion (Bandwidth limitation) : the signal is widen
due to different propagation times (T)
W0 TW0
Transmitted pulse fiber Received pulse
Attenuation: the loss of signal in the fibre (e.g., 0.2 dB/km)

43. Dispersion:-
• Dispersion: is the spread and broadening pulse of light as it is guided through the fiber.
• There are four types of dispersion:-
• Modal dispersion: occurs when various modes of light follow different paths through the
fiber and arrive at the far end at different times. It occurs only in multimode fibers.
• Material (or chromatic ) dispersion: occurs because different wave lengths (colors) of light
travel at different velocities through the fiber.
• Wave guide dispersion: occurs because light travels in both the core and cladding at slight
different speeds. It is most significant in single-mode fibers.
• Polarization mode dispersion: occurs when the X and Y polarization states of a light signal
travel at different speeds through a fiber. This is similar to MODAL dispersion except that it
can be significant in single – mode fiber.
• The unit of dispersion for single mode step index fiber is
• Ps/ km.nm
• While the unit of dispersion for multimode step index and graded index is the MHz.

44. Gradient Index Glass slows down the faster light modes and speeds up the slower ones
Core
CladdingInput pulse
Output pulse
Source
Ray of light
MULTIMODE GRADED INDEX
62.5 / 125 µm (Core / Cladding)

45. • Dispersion
– Modus dispersion or Modal Delay (4000
different modes)
140 µm
100 µm
Multimode Step-Index

46. SINGLEMODE STEP INDEX
Core
CladdingLaser
Ray of light
Input pulse
Output pulse
No dispersion
9 / 125 µm (Core / Cladding)

47. Patch cords:
SC-SC UPC 9/125µm Single mode
Simplex Patch Cord
SC-SC UPC 9/125µm Single mode Duplex
Patch Cord
LC-LC UPC 9/125µm Single
mode Simplex Patch Cord
LC-LC UPC 9/125µm Single mode Duplex
Patch Cord

48. Single mode adapters:
SC Single mode Duplex AdapterSC Single mode Simplex Adapter
LC Single mode Duplex AdapterLC Single mode Simplex Adapter

49. Fiber optic closure
• Fiber color code
system
1. Blue
2. Orange
3. Green
4. Brown
5. Gray
6. White
7. Red
8. Black
9. Yellow
10. Violet
11. Pink
12. Aqua

50. Pigtails & Patch cords:

51. FSM-50S –Fujikura FUSION SPLICER

52. TOOL KIT: tools used for cable preparation

54. Fiber optic maintenance workshop tools & equipments:
No. item quantity
1 Human resources At least 3 persons(one Eng.
&two Technicians)
2 (closed environment) 4-wheel drive car 1
3 Optical time domain reflectometer 1
4 Splicing machines 2
5 Cable preparation tool kit for cable jointing 1
6 Closures 4
7 Fiber optic cable (required capacity) At least 300m
8 Generator(3kw) 1
9 Electric cable(reel of 25 m) 1
10 Electric lamp(for light during night) 2
11 Optical set(light source &power meter 1
12 Pig tails & patch cord 2 (for each)
13 Movable flash light 2

55. THANKS