Fibre Optics[1]

8/8/2019 Fibre Optics[1]

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Advanced Fibre OpticsAdvanced Fibre Optics


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OverviewOverview

IntroductionIntroduction

Composition of optical fibreComposition of optical fibre

Operation of the fibre optic systemOperation of the fibre optic system

Advantages and disadvantagesAdvantages and disadvantages Analog and digital communicationAnalog and digital communication

Two main types of cablesTwo main types of cables

Pulse SpreadingPulse Spreading

Transmission LossTransmission Loss InterviewsInterviews

ConclusionsConclusions


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IntroductionIntroduction

Fibre optics is being used to transmit television,

voice, and digital data signals by light waves

over flexible hair like threads of glass and

plastic. It has evolved into a system of greatimportance and use since the 1980s.

The advantages of fibre optics compared to

coaxial cable or twisted pair cable, are endless.

Millions of dollars are being spent to put light

wave communication systems into operation, as

a result of its performance.


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Composition of optical fibreComposition of optical fibre

Silica based glass or plastic filaments areSilica based glass or plastic filaments arespun and packed into bundles of severalspun and packed into bundles of severalhundreds or thousands. Bundles may behundreds or thousands. Bundles may beput together as rods or ribbons and sheets.put together as rods or ribbons and sheets.

These bundles are flexible and can beThese bundles are flexible and can betwisted and contorted to conduct light andtwisted and contorted to conduct light andimages around cornersimages around corners

The thin glass center of the fibre where theThe thin glass center of the fibre where thelight travels is called the core.light travels is called the core.

The outer optical material surrounding theThe outer optical material surrounding thecore that reflects the light back into the corecore that reflects the light back into the coreis called the cladding.is called the cladding.

In order to protect the optical surface fromIn order to protect the optical surface frommoisture and damage, it is coated with amoisture and damage, it is coated with a

layer of buffer coating.layer of buffer coating.

Cross section of a bundle


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Light is ejected into the glassLight is ejected into the glass

core at the correct angle andcore at the correct angle and

transmitted; it will reflect backtransmitted; it will reflect back

repeatedly with internalrepeatedly with internal

reflections, even when the rodreflections, even when the rodis curved. Light cannot escapeis curved. Light cannot escape

from a fibre optics cable. Afrom a fibre optics cable. A

bundle of rods of fibres isbundle of rods of fibres is

capable of taking an imagecapable of taking an image

projected at one end of theprojected at one end of the

bundle and reproducing it atbundle and reproducing it atthe other end.the other end. Reflected path of light in the glass rod


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In a fibre optic system, there are a few major components to performIn a fibre optic system, there are a few major components to perform

the task of communicationthe task of communication..

The Input Modulator is needed; this modulates the incoming signalThe Input Modulator is needed; this modulates the incoming signal

with a light beam.with a light beam.

A light emitting device is used; it can be either a light emitting diodeA light emitting device is used; it can be either a light emitting diode(LED) or a semiconductor laser diode.(LED) or a semiconductor laser diode.

A fibre optic cable is used as a transportation medium.A fibre optic cable is used as a transportation medium.

A fibre optic system converts an electrical signal to an infrared lightA fibre optic system converts an electrical signal to an infrared light

signal, and then transmits the signal onto an optical fibre.signal, and then transmits the signal onto an optical fibre.

An Output Modulator is used to separate the signal from the lightAn Output Modulator is used to separate the signal from the lightbeam.beam.

Special connectors must be used to couple the light from the sourceSpecial connectors must be used to couple the light from the source

to the fibre and from the fibre to the detector.to the fibre and from the fibre to the detector.


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Advantages and DisadvantagesAdvantages and Disadvantages

ADVANTAGESADVANTAGES

Fibre optic cables have a much greater bandwidth than metal cables.Fibre optic cables have a much greater bandwidth than metal cables.

Fibre optic cable is less susceptible to signal degradation than copper wire.Fibre optic cable is less susceptible to signal degradation than copper wire.

Fibre optic cables weigh less than a copper wire cable.Fibre optic cables weigh less than a copper wire cable. Data can be transmitted digitally.Data can be transmitted digitally.

LowerLower--power transmitters can be used instead of the highpower transmitters can be used instead of the high--voltage electricalvoltage electricaltransmitters used for copper wires.transmitters used for copper wires.

Unlike electrical signals in copper wires, light signals from one fibre do notUnlike electrical signals in copper wires, light signals from one fibre do notinterfere with those of other fibres in the same cable.interfere with those of other fibres in the same cable.

Because no electricity is passed through optical cable it is nonBecause no electricity is passed through optical cable it is non--flammable,flammable,and immune to lightning.and immune to lightning.

Impossible to tap into a fibre optics cable, making it more secureImpossible to tap into a fibre optics cable, making it more secure


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Advantages and DisadvantagesAdvantages and Disadvantages

DISADVANTAGESDISADVANTAGES

Fibre optics are that the cables are expensive to install.Fibre optics are that the cables are expensive to install.

The termination of a fibre optics cable is complex and requiresThe termination of a fibre optics cable is complex and requires

special tools.special tools.

They are more fragile than coaxial cable.They are more fragile than coaxial cable.


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Analog and Digital CommunicationAnalog and Digital Communication

An analog signal changes continuously, while a digital signal can beAn analog signal changes continuously, while a digital signal can beat only a certain number of discrete levels.at only a certain number of discrete levels.

Conventionally, analog is used for audio and video communication.Conventionally, analog is used for audio and video communication.

Analog technology has been used because our ears detectAnalog technology has been used because our ears detectcontinuous fluctuations in sound levels, not just the presence orcontinuous fluctuations in sound levels, not just the presence orabsence of sound.absence of sound.

Going through a system where the analog signal can not beGoing through a system where the analog signal can not besuccessfully reproduced outputs a distorted signal which is whatsuccessfully reproduced outputs a distorted signal which is whathappens when we get a distorted voice on the telephone or radio.happens when we get a distorted voice on the telephone or radio.

Digital transmission works the best; both analog and digital signalsDigital transmission works the best; both analog and digital signalsare found in audio and telephone systems.are found in audio and telephone systems.

Analog signals are converted to digital before transmission and thenAnalog signals are converted to digital before transmission and thenback to analog signals.back to analog signals.


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Two main types of cablesTwo main types of cablesStep Index FibreStep Index Fibre This cable has a specific index of refractionThis cable has a specific index of refraction

for the core and the cladding.for the core and the cladding. It causesIt causes

deformations due to the various paths lengthsdeformations due to the various paths lengths

of the light ray.of the light ray. This is called modalThis is called modal

distortion. It is the cheapest type of cabling.distortion. It is the cheapest type of cabling.

Within the cladding and the core, theWithin the cladding and the core, therefractive index is constant.refractive index is constant.

Graded Index FibreGraded Index Fibre

In graded index fibre, rays of light followIn graded index fibre, rays of light follow

sinusoidal paths. Although the paths aresinusoidal paths. Although the paths are

different lengths, they all reach the end of thedifferent lengths, they all reach the end of the

fibre at the same time. Multimode dispersionfibre at the same time. Multimode dispersionis eliminated and pulse spreading is reduced.is eliminated and pulse spreading is reduced.

Graded Index fibre can hold the sameGraded Index fibre can hold the same

amount of energy as multimode fibre. Theamount of energy as multimode fibre. The

disadvantage is that this takes place at onlydisadvantage is that this takes place at only

one wavelength.one wavelength.


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Pulse SpreadingPulse Spreading

Optical fibres that carry data consist of pulses of lightOptical fibres that carry data consist of pulses of light

energy following each other. The fibre has a limit as toenergy following each other. The fibre has a limit as to

how many pulses per second can be sent to it and behow many pulses per second can be sent to it and be

expected to emerge intact at the other end. This isexpected to emerge intact at the other end. This is

known as pulse spreading which limits the Bandwidth ofknown as pulse spreading which limits the Bandwidth of

the fibre.the fibre.

The pulse sets off down the fibre with a square waveThe pulse sets off down the fibre with a square wave

shape. As it travels along the fibre, it progressively getsshape. As it travels along the fibre, it progressively gets

wider and the peak intensity decreases.wider and the peak intensity decreases.


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Transmission LossTransmission Loss

The transmission loss or attenuation of an optical fibre isThe transmission loss or attenuation of an optical fibre is

perhaps the most important characteristic of the fibre;perhaps the most important characteristic of the fibre;

this determines if a system is practical. It controls (1)this determines if a system is practical. It controls (1)

spacing between repeaters and (2) the type of opticalspacing between repeaters and (2) the type of optical

transmitter and receiver to be used.transmitter and receiver to be used.

As light waves travel down an optical fibre, they lose partAs light waves travel down an optical fibre, they lose part

of their energy because of various imperfections in theof their energy because of various imperfections in thefibre. These losses are measured in decibels perfibre. These losses are measured in decibels per

kilometers (dB/km).kilometers (dB/km).


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InterviewsInterviews

Kushner, Jeff, Fibre Solutions Specialist, CORNINGKushner, Jeff, Fibre Solutions Specialist, CORNING

Stated fibre optics is a revolution that may affect our lives as much asStated fibre optics is a revolution that may affect our lives as much as

computers and integrated circuits have. Fibre optics is beingcomputers and integrated circuits have. Fibre optics is being

compared in importance with microwave and satellite transmissions incompared in importance with microwave and satellite transmissions in

the advanced world of communications.the advanced world of communications.

Ali, Zafar, Configuration Supervisor, Unisys Canada Inc.Ali, Zafar, Configuration Supervisor, Unisys Canada Inc.

stated that fibre optics will make using devices that use services suchstated that fibre optics will make using devices that use services such

as twoas two--way television that was too costly before the development ofway television that was too costly before the development of

fibre optics easier to use with better quality. In addition to an incrediblefibre optics easier to use with better quality. In addition to an incrediblebandwidth, fibre optics has smaller and lighter cables thanbandwidth, fibre optics has smaller and lighter cables than

conventional copperconventional copper--conductor systems, with immunity to electricalconductor systems, with immunity to electrical

noise, and numerous other advantages.noise, and numerous other advantages.


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ConclusionConclusion The age of optical communications is a new era. In several waysThe age of optical communications is a new era. In several ways

fibre optics is a pivotal breakthrough from the electricfibre optics is a pivotal breakthrough from the electric

communication we have been accustomed to. Instead of electronscommunication we have been accustomed to. Instead of electrons

moving back and forth over a regular copper or metallic wire to carrymoving back and forth over a regular copper or metallic wire to carry

signals, light waves navigate tiny fibres of glass or plastic tosignals, light waves navigate tiny fibres of glass or plastic to

accomplish the same purpose.accomplish the same purpose. With a bandwidth and information capacity a thousand times greaterWith a bandwidth and information capacity a thousand times greater

than that of copper circuits, fibre optics may soon provide us with allthan that of copper circuits, fibre optics may soon provide us with all

the communication technology we could want in a lifetime, at a costthe communication technology we could want in a lifetime, at a cost

efficient price.efficient price.

Any new communication system that does not use fibre optics, orAny new communication system that does not use fibre optics, orconsider its use, is obsolete even before it has been built. It isconsider its use, is obsolete even before it has been built. It is

apparent that the average technician may also become supersededapparent that the average technician may also become superseded

if he or she fails to master fibre optics. After all, the technician will beif he or she fails to master fibre optics. After all, the technician will be

responsible for repairing and maintaining fibre- optic systemsresponsible for repairing and maintaining fibre- optic systems

wherever they are used, not the engineer.wherever they are used, not the engineer.


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THE ENDTHE END

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Fibre Optics[1]