Fiber Optic Power Point

8/13/2019 Fiber Optic Power Point

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What is fiber optics?

A technology that uses glass (or plastic) threads(fibers) to transmit data. A fiber optic cable consistsof a bundle of glass threads, each of which is capable

of transmitting messages modulatedonto lightwaves.

fiber opticsis a medium for carrying information from

one point to another in the form of light. Unlike thecopper form of transmission, fiber optics is notelectrical in nature.
http://www.webopedia.com/TERM/F/data.htmlhttp://www.webopedia.com/TERM/F/modulate.htmlhttp://www.corningcablesystems.com/web/news/dsprgall.nsf/ehtml/glossaryhttp://www.corningcablesystems.com/web/news/dsprgall.nsf/ehtml/glossaryhttp://www.webopedia.com/TERM/F/modulate.htmlhttp://www.webopedia.com/TERM/F/data.html


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Typical Fiber Optics


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Parts Of A Fiber Optics


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Parts Of A Fiber Optics

CoreGlass of plastic with a higher index ofrefraction than the cladding. Carries the signal

CladdingGlass or plastic with a lower index ofrefraction than the core.

BufferProtects the fiber from the damage andmoisture.

JacketHolds one or more fibers in a cable.


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History Of Fiber Optics

In 1880, Alexander Graham Bell experimented withan apparatus called photophone.

Photophonewas a device constructed from mirrorsand selenium detectors that transmitted sound wavesover a beam of light.

In 1930, J.L Baird and C.W Hansell were grantedpatents for scanning and transmitting TV imagesthrough uncoated fiber cables


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A German scientist named H. Lamm successfullytransmitted the images through single glass fiber.

In 1951, A.C.S van Heel, H.H Hopkins and N.SKapany experimented with light transmission throughbundles of fibers.

Their studies led to the development of the flexiblefiberscope,

which is used extensively in medical field.



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In 1958, Charles H. Townes and Arthur L. Schawlowwrote a paper describing how it was possible to use asimulated emission for amplifying light waves as wellas microwaves.

The laser (light amplification by stimulated emission ofradiation) was invented in 1960.

The lasers relatively high output power, highfrequency of operation and capability of carrying anextremely wide bandwidth signal make it ideally suitedfor high-capacity communications system.



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1967, K.C Kao and G.A Bockham proposed a newcommunications medium using cladded fiber cables

In late 1970s and early 1980s, the refinement ofoptical cables and the development of high-quality,affordable light sources and detectors opened the doorto the development of high-quality, high-capacity,

efficient, and affordable fiber optics communications.

1980s, losses in fiber optics were reduced to as low as0.16 dB/Km.



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1988, the American National Standards Institute(ANSI) published the Synchronous Optical Network(SONET).

By mid 1990s, optical voice and data networks werecommomplace throughout the US and much of theworld.

ElectronicCommunications Systemsby Wayne Tomasi



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Optical Fibers

A frisbeeilluminated byfiber optics
http://en.wikipedia.org/wiki/Frisbeehttp://en.wikipedia.org/wiki/Frisbee


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The touch of fiber optics

Fiber Optics Extender


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Origin Of Fiber Optic Communications

The French user semaphores to transmit messages inthe 1790s Later systems also sent optical signalsthrough the air

Light in a stream of water stays inside the water andbends with it. This was first demonstrated in the1840s


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During 1920-1950, thin, flexible rods of glass orplastic were used to guide light such bare fibersrequire air outside each fiber.

Developed in 1954 by van Heel, Hopkins and Kapany.Cladding is a glass or plastic cover around the core.Protects the total-reflection surface contamination.


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Medical Imaging, by 1960 glass-clad fibers wereavailable for medical instruments, to look inside thebody.

The glass used for medical purposes was unable totransmit light far for communications, because ofimpurities


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Medical probe using fiber optics


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Charles Kao developed a fiber that could transmit1GHz (One billion bits per second). But attenuationwas 1000 dB/Km, so it could not transmit light far

enough for practical communications.

Corning scientists developed low attenuation silicaglass fibers in 1970.


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In 1977, Telephone signals used infraredlight with a wavelength of 850 nm to senddata at 6.2 Mbps and 45 Mbps. Loss was 2dB/Km.

TAT-8, In 1988 AT&T laid the first fiber optictransatlantic telephony cable 3,148 mileslong. Connected North America to France.


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The process of laying the cables of TAT-8


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FIBER AMPLIFIER

Special fiber with Erbium atoms in it used to amplifylight without changing it to an electrical signal first.

It uses stimulated emission, the same principle thatmakes lasers work.


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Erbium Doped Fiber Amplifier

cladding-pumped fiber amplifier


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Wavelength Division Multiplexing (WDM)

Several signals can be sent trough the same fibersimultaneously by using different wavelengths (colors)of light.

fibre-optic communications, wavelength-divisionmultiplexing (WDM) is a technology which multiplexesmultiple optical carriersignals on a single optical fibreby using different wavelengths(colours) of laserlightto carry different signals.
http://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Multiplexinghttp://en.wikipedia.org/wiki/Optical_Carrierhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Laserhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Laserhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Optical_Carrierhttp://en.wikipedia.org/wiki/Multiplexinghttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Fiber-optic_communication


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Dense Wavelength Division Multiplexing(DWDM)

DWDM works by combining and transmitting multiplesignals simultaneously at different wavelengths onthe same fiber. In effect, one fiber is transformed

into multiple virtual fibers.

Dense wavelength-division multiplexing (DWDM)revolutionized data transmission technology by

increasing the capacity signal of embedded fiber.
http://www.webopedia.com/TERM/D/Fibre_Channel.htmhttp://www.webopedia.com/TERM/D/Fibre_Channel.htm


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DWDM sample process

Actual DWDM device

Fiber Optics Handouts


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Types Of Fiber Optics

Understanding the characteristics of different fibertypes aides in understanding the applications forwhich they are used. Operating a fiber optic system

properly relies on knowing what type of fiber is beingused and why. There are two basic types of fiber:multimode fiber and single-mode fiber.


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Multimode fiber is best designed for shorttransmission distances, and is suited for use in LANsystems and video surveillance. Single-mode fiber is

best designed for longer transmission distances,making it suitable for long-distance telephony andmultichannel television broadcast systems.


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Single Mode

Single-mode fiber allows for a higher capacity totransmit information because it can retain thefidelity of each light pulse over longer distances,and it exhibits no dispersion caused by multiplemodes

Single-mode fiber also enjoys lower fiberattenuation than multimode fiber


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Modern single-mode fibers have evolved into morecomplex designs such as matched clad, depressedclad and other exotic structures.

Single-mode fibers experience nonlinearities that cangreatly affect system performance. For completeinformation.


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Advantages of Single Mode Fiber

Single mode fiber doesnt have modal dispersion,

modal noise, and other effects that come with

multimode transmission; single mode fiber can carry

signals at much higher speeds than multimode fibers.


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Advantages of Single Mode Fiber

They are standard choice for high data rates or long

distance span (longer than a couple of kilometers)

telecommunications which use laser diode based

fiber optic transmission equipment.


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Disadvantages of Single Mode Fiber

Since single mode fibers core is so much

smaller than a multimode fibers core,

coupling light into single mode fiber requires

much tighter tolerances than coupling light into the

larger cores of multimode fiber.


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Disadvantages of Single Mode Fiber

Single mode fiber components and equipment are

also more expensive than their multimodecounterparts, so multimode fibers are widely used insystems where connections must be madeinexpensively and transmission distances and speedsare modest.


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What Are the Conditions for Single Mode Transmission?To calculate the number of modes Nmin a step-index fiber, Nm can besimplified as:

WhereDis core diameter of the fiberis the operating wavelengthnfis refractive index of the fiber corencis refractive index of the fiber cladding


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Reducing the core diameter sufficiently can limittransmission to a single mode. The following formuladefines the maximum core diameter, D, which limits

transmission to a single mode at a particularwavelength, :

If the core is any larger, the fiber can carry two modes.

www.fiberoptics4sale.com


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Multimode fiber

is made of glass fibers, with a common diameters inthe 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 promisesperformance similar to glass cable on very short runs,

but at a lower cost.


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Multimode fiber

Multimode fiber gives you high bandwidth at highspeeds over medium distances. Light waves are

dispersed into numerous paths, or modes, as theytravel through the cable's core typically 850 or1300nm.


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Multimode fiber

Multimode fiber, the first to be manufactured andcommercialized, simply refers to the fact that

numerous modes or light rays are carriedsimultaneously through the waveguide.

Multimode fiber may be categorized as step-indexorgraded-indexfiber.


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Multimode Step-index Fiber

A multimode step-index fiber has a core of radius anda constant refractive index. A cladding of slightly

lower refractive index surrounds the core.

Three different lightwaves travel down the fiber of amultimode step-index fiber.


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Total Internal Reflection in Multimode Step-index fiber


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Multimode Graded-index FiberGraded-index refers to the fact that the refractiveindex of the core gradually decreases farther from

the center of the core.

The cores central refractive index, is greater thanthat of the outer cores refractive index,


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Multimode Graded-index Fiber


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Advantages of Multimode fiber

A large core size and a higher NA have severaladvantages.

Light is launched into a multimode fiber withmore ease.

The higher NA and the larger core size make iteasier to make fiber connections.


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Advantages of Multimode fiber

Another advantage is that multimode fibers permitthe use of light-emitting diodes (LEDs)

LEDs are cheaper, less complex, and last longer.LEDs are preferred for most applications.


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Disadvantages of multimode fiber

As the number of modes increases, the effect ofmodal dispersion increases.

Modal dispersion affects system bandwidth. Fibermanufacturers adjust the core diameter, NA, andindex profile properties of multimode fibers to

maximize system bandwidth.


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www.fiber-optics.info


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OPTICAL FIBERS VS METALLIC CABLES

Advantages of Optical Fibers

Wider bandwidth and greater information capacity.

Immunity to crosstalk.

Immunity to static interference.

Environmental immunity.


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Advantages of Optical Fibers

Safety and convenience.

Lower transmission loss.

Security.

Durability and reliability

Economics.


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Disadvantages of Optical Fibers

Interfacing costs.

Strength.

Remote electrical power.

Optical fiber cables are more susceptible to lossesintroduced by bending the cable.

Specialized tools, equipment, and training.


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ELECTROMAGNETIC SPECTRUM

The electromagnetic (EM) spectrum is the range ofall possible electromagnetic radiation. Also the"electromagnetic spectrum" (usually just spectrum)

of an object is the frequency range ofelectromagnetic radiation with wavelengths fromthousands of kilometresdown to fractions of the sizeof an atom.
http://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Kilometrehttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Kilometrehttp://en.wikipedia.org/wiki/Electromagnetic_radiation


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The light frequency spectrum can be dividedinto three general bands:

Infrared

Visible

Ultraviolet


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Electromagneticfrequency spectrum


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Electromagnetic energy at a particularwavelength(in vacuum) has an associatedfrequencyfand photonenergyE. Thus, theelectromagnetic spectrum may be expressedequally well in terms of any of these threequantities. They are related according to theequations:

wave speed(c) = frequencyx wavelength


Electronic Communications Systems

by Wayne Tomasi
http://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Lambdahttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Lambdahttp://en.wikipedia.org/wiki/Wavelength


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FIBER OPTIC DATA COMMUNICATIONS LINK


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Light Propagation

Physics of Light

Light is simply a name for a range ofelectromagnetic radiation that can be detected by

the human eye.

Light is a complex phenomenon that isclassically explained with a simple model based

on rays and wavefronts


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Light Propagation

Plancks Law

When visible light or high-frequency electromagneticradiation illuminates a metallic surface, electrons are

emitted.

In 1905, Max Planck showed that when light isemitted or absorbed it behaves like an

electromagnetic wave.


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Light Propagation

Plancks Law

Ep = hf

where:

Ep= energy of the photon (joules)

h= Plancks constant 6.625x10^-34 J-sf = frequency of light (photon) emitted (hertz)


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Light Propagation

Optical power

Optical power (dioptric power or refractive power) isthe degree to which a lensor mirrorconverges or

diverges light. It is equal to the reciprocal of the focallengthof the device

The dioptreis the most common unit of

measurement of optical powe
http://en.wikipedia.org/wiki/Lens_%28optics%29http://en.wikipedia.org/wiki/Mirrorhttp://en.wikipedia.org/wiki/Focal_lengthhttp://en.wikipedia.org/wiki/Focal_lengthhttp://en.wikipedia.org/wiki/Dioptrehttp://en.wikipedia.org/wiki/Dioptrehttp://en.wikipedia.org/wiki/Focal_lengthhttp://en.wikipedia.org/wiki/Focal_lengthhttp://en.wikipedia.org/wiki/Mirrorhttp://en.wikipedia.org/wiki/Lens_%28optics%29


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Light Propagation

Optical power

d(energy)

P= --------------

d(time)

where:

P= optical power (watts)dQ= instantaneous charge (joules)

dt= instantaneous charge in time (seconds)


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Light Propagation

Velocity Of Propagation

Velocity of Propagation (VoP) or velocity factor is aparameter that characterizes the speed at which an

electrical signal passes through a medium.

This parameter is used for communication mediasuch as data cables.
http://en.wikipedia.org/wiki/Transmission_mediumhttp://en.wikipedia.org/wiki/Transmission_medium


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Light Propagation

Refraction

Refraction is the change in direction of a wavedue toa change in its speed. This is most commonly seen

when a wave passes from one mediumto another

Refraction of lightis the most commonly seenexample, but any type of wave can refract when it

interacts with a medium
http://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Speedhttp://en.wikipedia.org/wiki/Optical_mediumhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Optical_mediumhttp://en.wikipedia.org/wiki/Speedhttp://en.wikipedia.org/wiki/Wave


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Light Propagation

Refractive index

The refractive index (or index of refraction) of amedium is the inverse ratio of the phase velocityof a

wavephenomenon such as lightor soundand thephase velocity in a reference medium.

It is usually given the symbol n. In the case of light.
http://en.wikipedia.org/wiki/Refractionhttp://en.wikipedia.org/wiki/Phase_velocityhttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Phase_velocityhttp://en.wikipedia.org/wiki/Refraction


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Light Propagation

Refractive index

where:

n= refractive index (unitless)c = speed of light (3x10^8 meters/second)

v = speed of light in a given material (meters/s)


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Light Propagation

Snells Law

In opticsand physics, Snell's law (also known asDescartes' Law or the law of refraction), is a formula

used to describe the relationship between the anglesof incidence and refraction, when referring to light orother waves, passing through a boundary betweentwo different isotropicmedia, such as air and glass
http://en.wikipedia.org/wiki/Opticshttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Mathematical_formulahttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Isotropichttp://en.wikipedia.org/wiki/Medium_%28optics%29http://en.wikipedia.org/wiki/Medium_%28optics%29http://en.wikipedia.org/wiki/Isotropichttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Mathematical_formulahttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Optics


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Light Propagation

Snells Law

where:

n1 & n2 = refractive index of materials (unitless)Q1 & Q2= angle of incidence (degrees)


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Light Propagation

Critical Angle

the critical angle is defined as the angle of incidencewhich provides an angle of refraction of 90-degrees.

Make particular note that the critical angle is an angleof incidence value.

The actual value of the critical angle is dependentupon the combination of materials present on eachside of the boundary.


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Light Propagation

Critical Angle Critical Angle

where Qc is the angle from the normal, and n1andn2are the indices of refraction of the original andsecond media.


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OPTICAL FIBER CONFIGURATION

Light can be propagated down an optical fiber cableusing either reflection or refraction.

How the light propagates depends on the mode ofpropagationand the index profileof the fiber.


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Mode of Propagation

In fiber optics terminology, the word modesimplymeans path.

If there is only one path for light rays to take down acable, it is called single mode.

If it is more than path, it is called multimode.


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Mode of Propagation

Where:

N=nos. of propagating modes

d =core diameter

lambda=wavelength

n1 = refractive index core

n2 = refractive index of cladding

d


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Index Profile

The index profile of an optical fiber is a graphicalrepresentation of the magnitude of the refractive

index across the fiber.

There are two types of index profiles: stepandgradedindex profile.


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Step-index profile

For an optical fiber, a step-index profile is a refractiveindexprofile characterized by a uniform refractive

index within the coreand a sharp decrease inrefractive index at the core-claddinginterfaceso thatthe cladding is of a higher refractive index.
http://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Refractive_indexhttp://en.wikipedia.org/wiki/Refractive_indexhttp://en.wikipedia.org/w/index.php?title=VFiber_optics&action=edithttp://en.wikipedia.org/wiki/Claddinghttp://en.wiktionary.org/wiki/interfacehttp://en.wiktionary.org/wiki/interfacehttp://en.wikipedia.org/wiki/Claddinghttp://en.wikipedia.org/w/index.php?title=VFiber_optics&action=edithttp://en.wikipedia.org/wiki/Refractive_indexhttp://en.wikipedia.org/wiki/Refractive_indexhttp://en.wikipedia.org/wiki/Optical_fiber


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Step-index profile

The step-index profile corresponds to a power-lawindex profilewith the profile parameter approaching

infinity. The step-index profile is used in most single-mode fibersand some multimode fibers.
http://en.wikipedia.org/wiki/Power-law_index_profilehttp://en.wikipedia.org/wiki/Power-law_index_profilehttp://en.wikipedia.org/wiki/Single-mode_fiberhttp://en.wikipedia.org/wiki/Single-mode_fiberhttp://en.wikipedia.org/wiki/Multimode_fiberhttp://en.wikipedia.org/wiki/Multimode_fiberhttp://en.wikipedia.org/wiki/Single-mode_fiberhttp://en.wikipedia.org/wiki/Single-mode_fiberhttp://en.wikipedia.org/wiki/Single-mode_fiberhttp://en.wikipedia.org/wiki/Power-law_index_profilehttp://en.wikipedia.org/wiki/Power-law_index_profilehttp://en.wikipedia.org/wiki/Power-law_index_profilehttp://en.wikipedia.org/wiki/Power-law_index_profile


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Step-index profile

n1 is typically between 1.44 and 1.46, and is typicallybetween 0.001 and 0.02.


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LOSSES IN OPTICAL FIBER CABLES

Power lossin an fiber cable is probably the most

important characteristic of the cable. Power loss is

often called attenuationand results in reduction in

the power of the light wave as it travels down the

cable.


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Power loss

A(dB) = 10 log (Pout/Pin)

Where:

A(dB)= total reduction in power level, attenuation

P out= cable power output (watts)P in= cable power input (watts)


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Absorption Loss

That part of the transmission losscaused by the

dissipation or conversion of electrical,

electromagnetic, or acoustic energy into other forms

of energy as a result of its interaction with a material

medium.
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Three Factors contribute to Absorption Loss

Ultraviolet Absorptioncaused by valence electronsin the silica material.

Infrared Absorptionis a result of photons of lightthat are absorbed by the atoms of the glass core.

Ion resonance absorptionis caused by OH-

ions in the material


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Material, Rayleigh, Scattering Losses

The tension applied to the glass causes the coolingglass develop is in plastic state. The tension applied

to the glass causes the glass to develop permanentsubmicroscopic irregularities that causes thescattering of light rays which is called Reyleighscattering loss.


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Chromatic,or wavelength, dispersion

In optics, dispersion is a phenomenon that causesthe separation of a waveinto spectral components

with different wavelengths, due to a dependence ofthe wave's speed on its wavelength. Dispersion issometimes called chromaticdispersion to emphasizeits wavelength-dependent nature.
http://en.wikipedia.org/wiki/Opticshttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Wavelengthshttp://en.wikipedia.org/wiki/Wavelengthshttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Optics


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Modal Dispersion

Sometimes called pulse spreading, is caused by thedifference in the propagation times of light rays that

take different paths down a fiber.

Modal dispersion can cause a pulse of light energy tospread out in time as it propagates down a fiber.


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Coupling Losses

Coupling loss also known as connection loss is theloss that occurs when energyis transferred from one

circuit, circuit element, or medium to another.

Coupling loss in fiber opticsrefers to the power lossthat occurs when coupling light from one optical

device or medium to another.

Electronic Communications Systems by Wayne Tomasi
http://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Electrical_circuithttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Electrical_circuithttp://en.wikipedia.org/wiki/Energy


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LIGHT SOURCES

Light sources used for optical fiber systems must beat wavelengths efficiently propagated by the opticalfiber.

In addition, the range of wavelengths must beconsidered because the wider the range, the morelikely the chance that chromatic dispersion will occur


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OPTICAL SOURCES

There are essentially only two types of practical lightsources used to generate light for optical fibercommunications systems:

LEDs and ILDs, both devices are constructed fromsemiconductor materials and have advantages anddisadvantages.


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OPTICAL SOURCES

LEDs

An LED is a p-n junction diode, usually made from asemiconductor material such as aluminum-gallium-

arsenide or gallium-arsenide-phospide.

LEDs emit lights by spontaneous emissionlight isemitted as a result of recombination of electrons and

holes.


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Light Emitting Diodes (LED)


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OPTICAL SOURCES

Homojunctions LEDs

A p-n junction made from two differents mixtures ofthe same types of atoms is called homojunction

structure.

The simplest LED structures are homojunction andepitaxially grown or they single diffused

semiconductor devices.


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O C SO C S


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OPTICAL SOURCES

Heterojunction LEDs

are made from a p-type semiconductor material ofone set of atoms and an n-type semiconductor

material from another set.

The light emitted from the edge of the material andare therefore often called edge emitters.


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Emission of Light of a heterojunction LED.

OPTICAL SOURCES


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OPTICAL SOURCES

Burrus Etched-Well Surface-EmittingLEDs

it emits light in many directions. The etched wellhelps concentrate the emitted light to a very smallarea.

These devices are more efficient than the standardsurface emitters, and they allow more power to becoupled into optical fiber.

OPTICAL SOURCES


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OPTICAL SOURCES

Edge-Emitting LED

These LEDs emit a more directional light

pattern than do the surface-emitting LEDs.

The construction is similar to the planar and

Burrus diodes except that the emitting surface

is a stripe rather than a confined circular area.


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Edge-emitting LEDS

OPTICAL SOURCES


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OPTICAL SOURCES

ILD

Is similar to the LED. In fact, below a certainthreshold current, an ILD acts similarly to an LED.

Above the threshold current, an ILD oscillates; laseroccurs.

As current passes through a forward biased p-njunction diode, light is emitted by spontaneous

emission at a frequency determined by the enrgy gapof the material.

LIGHT DETECTORS


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LIGHT DETECTORS

PIN Diodes

A PIN Diodes is a depletion-layer photodiode and is

probably the most common device used a light

detector in fiber-optic communications systems.

PIN photodiode operates just the opposite of an LED

LIGHT DETECTORS


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LIGHT DETECTORS

PIN Diodes

Photoelectric effect

The photoelectric effect is a quantumelectronic

phenomenon in which photoelectronsare emittedfrom matter after the absorption of energy fromelectromagnetic radiationsuch as x-rays. Study ofthe photoelectric effect led to important steps in

understanding the quantum nature of light.

LIGHT DETECTORS
http://en.wikipedia.org/wiki/Quantum_mechanicshttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Quantum_mechanics


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LIGHT DETECTORS

APDs

An APD is a pipnstructure. Light enters the diodeand is absorbed by the thin, heavily doped n-layer.

A high electric field intensity developed across thei-p-njunction by reverse bias causes impact ionizationto occur.


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Construction of APDs

Electronic Communications Systems by Wayne Tomasi

LASER


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LASER

Laser is an acronym for light amplificationstimulated by the emission of radiation.

Laser technology deals with theconcentration of light into a very small,powerful beam.

The first laser developed by Theodore H.Mainan.

LASER


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LASER

Laser Types

Gas Lasers use a mixture of helium andneon enclosed in a glass tube.

Liquid Lasers use organic dyes enclosed ina glass tube.

Solid Lasers uses a solid cylindrical crystal.

Semiconductor Lasers made up of pn

semiconductors


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Semiconductor Laser


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Beam of Solid Laser

Process of Gas Laser


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Gas Laser


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Actual Liquid Laser

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