Fiber Optics

Topics: Optical fiber, Refractive index, Total internal reflection Pages: 27 (903 words) Published: April 21, 2015
Fiber Optics

History of Fiber Optics

History Of Fiber Optics
In 1870, John Tyndall, using a jet of
water that flowed from one container
to another and a beam of light,
demonstrated that light used internal
reflection to follow a specific path.

• Alexander Graham Bell patented an
optical telephone system, which he
called the Photophone
• He dreamed of sending signals
through the air, but the atmosphere
didn't transmit light as reliably as
wires carried electricity.

• During the 1920s, John Logie Baird
in England and Clarence W. Hansell
in the United States patented the
idea of using arrays of hollow pipes
or transparent rods to transmit
images for television or facsimile
systems.

• In 1954s, Abraham Van Heel made the
crucial innovation of cladding fiber-optic
cables
• Abraham Van Heel covered a bare fiber or
glass or plastic with a transparent
cladding of lower refractive index.

• Corning Glass researchers Robert
Maurer, Donald Keck, and Peter
Schultz invented fiber-optic wire or
"optical waveguide fibers

• In April 1977, General Telephone
and Electronics tested and deployed
the world's first live telephone traffic
through a fiber-optic system running
at 6 Mbps, in Long Beach,
California.
• Today more than 80 percent of the
world's long-distance voice and data
traffic is carried over optical-fiber
cables.

What are Fiber Optics?

What are Fiber Optics?
 Core - Thin glass center of
the fiber where the light
travels
 Cladding - Outer optical
material surrounding the
core that reflects the light
back into the core
 Buffer coating - Plastic
coating that protects the
fiber from damage and
moisture

Optical fibers come in two/three
types:
 Single-mode fibers
 All signals travel straight
down the middle without
bouncing off the edges (red
line in diagram).
 Eg. Cable TV, Internet, and
telephone signals.
 Multi-mode fibers
 10 times bigger than one in a
single-mode cable.
 Transmit infrared light
(wavelength = 850 to 1,300
nm) from light-emitting
diodes (LEDs).

 Plastic fibers
 Have a large core (0.04
inches or 1 mm
diameter) and transmit
visible red light
(wavelength = 650 nm)
from LEDs.
 adequate for running
short links, such as
inside of instruments or
within a room for
desktop connections up
to 50 meters. And of
course in automobiles

How Are Fiber Optics made?

How are optical fibres made?
Step 1--Create the Fibre Optic
Preform
• Modified Chemical Vapor Deposition
(MCVD)
• Bubbling oxygen through chemical
solutions
• Gas produced is directed into the tube
• Provide high temperature to cause the gas
to react with oxygen
• Silicon dioxide and Germanium dioxide
produced caused the tube to fuse
together

Step 2-Draw optical fibre from the
preform
• The finished glass perform is installed on the
top of a tower.
• Lowering one end of the perform into an in-line
furnace.
• High temperature caused the end of perform to
melt and form a molten glob.
• The glob is pulled downward by gravity,
produced a thin stand of glass.
• The operator connect the fibre to a tractor
mechanism.
• The tractor pulls the glass stand at very high
speed.
• The complete fibre is wound onto a spool.

Step 3-Testing the finished
optical fibre








Tensile strength
Refractive index profile
Fibre geometry
Attenuation
Information carrying capacity
Chromatic dispersion
Operating temperature

How Fiber Optics
Work?

How Does an Optical Fiber Transmit
Light?
• Principles of reflection and refraction:
 Light refracts when travelling between two substances of different density.
 At a certain angle, light reflects back into the original substance completely.


To keep light in the fiber optic :
 Structure of cable
 Total internal reflection

Structure of the cable:
• Core
 The bit the light travels through.
• Cladding
 Lower refractive index than the core...
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