OPTICAL FIBERS

1. Shantilal Shah
Engineering College,
Bhavnagar
INSTRUMENTATION AND CONTROL
ENGINEERING
( SEMESTER 1 )
1
Sidsar Campus, P.O. Vartej, Bhavnagar-364060
Phone: 0278-2445509, 2445767
Fax: 0278-2445509
Website: http://www.ssgec.ac.in/

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OUR GROUP
Members :
1. Jitin J Pillai
2.Dodiya Siddhraj
3.Kaneriya Yash
4.Dodiya Parth
5.Tripathi Vishal

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INTRODUCTION
Optical Fibers are hair-thin,
transparent strands through
which light can be transmitted.
A group of many such optical
fibers constitute a Optical Fiber
Cable.

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CONSTRUCTION
The main parts of an optical fiber are :
Core – thin glass center of the fiber
where light travels.
Cladding – outer optical material
surrounding the core.
Buffer Coating – plastic coating that
protects
the fiber.
Other protective coatings.

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PRINCIPLE
TOTAL INTERNAL REFLECTION is the main principle behind the
working of an optical fiber.
For T.I.R., conditions are satisfied :
• Light is incident on the walls of the cable at an angle greater than
the critical angle.
• The optical-fiber core is clad (coated) by a lower density glass
layer.

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FIBER TYPES
1. Plastic core and Plastic cladding
2. Glass core with Plastic cladding PCS (Plastic-Clad
Silicon)
3. Glass core and Glass cladding SCS (Silica-clad
silicon)
4. Under research: Zinc-chloride (non-Silicate)
 1000 time as efficient as glass
ON THE BASIS OF MATERIAL :

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ON THE BASIS OF MODE OF PROPAGATION :
1. Singlemode Fiber :
 Only one path for the propagation of light.
 The core is made very small (about 7-10 µm).
2. Multimode Fiber :
 More than one paths for the propagation of light.
 Core is larger in diameter (about 20-100 µm).

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ON THE BASIS OF INDEX PROFILE
1. Step-Index Fiber :
 Refractive index of the core as well as the cladding
is uniform.
 Light rays propagate in the form of meridional rays,
i.e. they follow a zigzag path and, for every
reflection they will cross the fiber axis.
2. Graded Index Fiber (GRIN Fiber):
 Refractive index of the core is not uniform, while
that of the cladding is uniform.
 Light rays propagate in the form of skew rays, i.e.
they follow a helical path and will never cross the
fiber axis.

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FIBER CONFIGURATIONS
I. Singlemode Step-Index Fiber (SMSI Fiber)
Single-mode step-index Fiber
n1 core
n2 cladding
no air
Light
ray
Index of
refraction

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II. Multimode Step-Index Fiber
Multimode step-index Fiber
n2 cladding
n1 core
no air
Index of
refraction

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III. Multimode Graded Index Fiber
Variable
n
Index profile
Multimode graded-index Fiber
Index of
refraction

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ADVANTAGES OF OPTICAL FIBER
 Capacity: much wider bandwidth (10 GHz)
 Crosstalk immunity
 Immunity to static interference
 Lightning
 Electric fields
 Florescent light
 Higher environment immunity
 Weather, temperature, etc.
 Safety: Fiber is non-metallic.
 No explosion, no shock
 Lasts longer.
 Security: tapping is difficult
 Economics: Fewer repeaters
 Low transmission loss (dB/km)
 Fewer repeaters
 Less cable
Remember:
Fiber is non-conductive
Hence, change of magnetic
field has
No impact!

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DISADVANTAGES OF OPTICAL FIBER
 Higher initial cost in installation
 Interfacing cost
 Less strength
 Lower tensile strength
 Remote electric power
 More expensive to repair/maintain
 Tools: Specialized and sophisticated

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APPLICATIONS
In Telecommunications to
transfer data.
In Local Area Networks to
share internet connections.
In Cable TV and CCTV.
In Optical Fiber Sensors.
In Endoscopy to view
internal body organs.
In decoration.

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Input
Signal
Coder or
Converter
Light
Source
Source-to-Fiber
Interface
Fiber-to-light
Interface
Light
Detector
Amplifier/Shaper
Decoder
Output
Fiber-optic Cable
Receiver
OPTICAL FIBERS ARE USED IN
TELECOMMUNICATION
Transmitter

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OPTICAL FIBERS ARE USED IN ENDOSCOPIC
SURGERY

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THANK YOU