Fibre optics

INTRODUCTION
• Fibre optic technology is one of the fastest growing
technology.
• Optical fibre draw more interests of researchers and
engineers for its valuable characteristics.
• It is mainly used to sense the physical and chemical
properties such as strains, vibrations, accelerations, linear
and rotary position.
• It is also used to sense temperatures, pressures, determination
of pH, refractive index of liquid solution, pipeline condition
monitoring etc.

DEFINITION
• An Optical fibre is a transparent guiding medium or material
which guides the information carrying light waves.
• It is made of glass or plastic.
• It can function as a light pipe to transmit light between the
two ends of the fibre.
• Optical fibres are widely used in fiber-optic
communications.
• The field of applied science and engineering concerned with
the design and application of optical fibres is known as
Fibre optics.

HISTORY
• In the 1840s, physicists Daniel Collodon and Jacques
Babinet showed that light could be directed along jets of
water .
• In 1854, John Tyndall, physicist, demonstrated that light
could travel through a curved stream of water.
• Alexander Graham Bell patented an optical telephone system
called the photo phone in 1880.

PRINCIPLE OF OPERATION
• Index of refraction: It is a way of measuring the speed of
light in a material. Light travels fastest in a vacuum, such
as in outer space
• Total Internal Reflection: When light is travelling in an
optically dense medium hits a boundary at a steep angle the
light is completely reflected. This is called total internal
reflection.

SINGLE AND MULTIMODE FIBRES
• Single-mode Fibre: In optical fibre technology, single mode
fibre is optical fibre that is designed for the transmission of a
single ray or mode of light as a carrier and is used for long-
distance signal transmission.
• Multi-mode Fibre: In optical fibre technology, multimode
fibre is optical fibre that is designed to carry multiple light
rays or modes concurrently, each at a slightly different
reflection angle within the optical fibre core

CLASSIFICATION OF OPTICAL FIBRE
• Optical fibres are classified in to two types:
• 1.Step-Index Optical Fibre:The Refractive index of core
and cladding of a step index fibre is constant.
• Graded-Index Optical Fibre: In this type of fibre cone has
a non-uniform refractive index that gradually decrease
from the centre towards the core cladding interface

Attenuation
• Attenuation is the loss of the optical power. It takes place in
Optical fibre due to elements like coupler, splices, connector and
fibre itself.
• Attenuation may be categorised as Intrinsic and Extrinsic. The
specific attenuation actually depends on the wave length of the
radiation travelling along the Optic fibre.

Applications of Fiber Optics
Fiber Optic Technology has grown tremendously over the years and
today can be found in many surprising places.
Main Applications of Fiber Optics are:
 Communication Systems
 Medicine
 Sensors
 Military
 Electronics

Applications of Fiber Optics in Communication Systems.
• Fiber-optic communication is a method of transmitting
information from one place to another by sending pulses of light
through an optical fiber.
• Optical fiber is used by many telecommunications companies to
transmit telephone signals, Internet communication, and cable
television signals.

Process of Communication
• The process of communicating using fiber-optics involves the
following basic steps:
1. Creating the optical signal involving the use of a transmitter,
2. Relaying the signal along the fiber, ensuring that the signal does
not become too distorted or weak,
3. Receiving the optical signal, and converting it into an electrical
signal.

Technology
 Modern fiber-optic communication systems generally include an
 Optical transmitter : to convert an electrical signal into an
optical signal to send into the optical fiber.

Technology
 A Cable: containing bundles of multiple optical fibers.
 An Optical Receiver: to recover the signal as an electrical signal.

Fiber Optic Communication System

Advantages of Optical Fiber Communication
The life of fibre is longer than Copper wire.
Handling and Installation costs of Optical fiber are very nominal.
It is unaffected with electromagnetic Interference.
Attenuation in optical fibre is lower than coaxial cable or twisted pair.
There is no necessity of additional equipment for protecting against
grounding and voltage problems.
As it does not radiates energy any antenna or detector cannot detects it
hence provides signal security.
Extremely wide band width.

Applications of Fiber Optics in Medicine
• Fiber optics have been used in the medical industry for years. The
physical characteristics of fiber make it a natural choice for many
different applications.
• Fiber optics provide a very compact, flexible conduit for light or
data delivery in equipment, surgical, and instrumentation
applications.

Applications
• Traditional medical fiber optic applications include:
 Light therapy
 Ophthalmic lasers
 Lab and clinical diagnostics
 Endoscopy
 surgical microscopy
 Dental hand pieces

Applications in Sensors
• A fiber optic sensor is a sensor that uses optical fiber either as the
sensing element or as a means of relaying signals from a remote
sensor to the electronics that process the signals .
• They are widely used in sensors for sensing and measuring of
acoustic fields, magnetic fields,currents,acceleration,strain etc.,

Applications
• Fibre Optic Sensor holds particularly for harsh environments, such
as sensing in high-voltage and high-power machinery, or in
microwave ovens.
• Bragg grating sensors can also be used to monitor the conditions
e.g. within the wings of airplanes, in wind turbines, bridges, large
dams, oil wells and pipelines.

Applications in Military
• Fiber optic products are used in a variety of military applications.
• The Military uses fiber optic technology for a wide variety of air,
sea, ground, and space applications.
• Military fiber optic applications are highly specialized.

Applications in Electronics
• Fiber optic products for the electronics market cover a wide range
of applications.
• Typically used in professional audio/video, alarm/security, and
OEM component connections.

Future Applications
• In Research field, fiber is enabling the creation of clocks that are
more accurate before. By combining a laser with an optical fiber,
these clocks allow scientists to measure time accurately than they
have been able to previously, enabling better, more precise.

Disadvantages of Fiber Optics
• Highly skilled staff would be required for maintenance.
• Only point to point working is possible on Optical fibre.
• Precise and costly instruments would be required.
• Costly and Expensive.
• Jointing of Fibers is a Time consuming process.

Conclusion
• The age of optical communications is a new era.
• At present there are many optical fiber communication links
throughout the world without using optical solutions.
• We can expect a great revolution in optical fiber communication
within a few years by means of solutions.

Fibre optics

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