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The Origins of Fiber Optic Communications
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Transcript of The Origins of Fiber Optic Communications
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The Origins of FiberThe Origins of Fiber
Optic CommunicationsOptic CommunicationsCh 1Ch 1
Fiber Optics TechniciansFiber Optics TechniciansManual, 3Manual, 3rdrd. Ed. Ed
Jim HayesJim Hayes
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Early Optical CommunicationsEarly Optical Communications
The French used semaphores toThe French used semaphores to
transmit messages in the 1790stransmit messages in the 1790s
Later systems also sent opticalLater systems also sent opticalsignals through the airsignals through the air
But clouds, rain, and other atmosphericBut clouds, rain, and other atmospheric
disturbances can disrupt optical signalsdisturbances can disrupt optical signals
sent through the airsent through the air Electric signals through wires avoid thatElectric signals through wires avoid that
problemproblem Image from Wikipedia SemaphoresImage from Wikipedia Semaphores
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Guiding Light With WaterGuiding Light With Water
Light in a stream ofLight in a stream of
water stays insidewater stays inside
the water and bendsthe water and bends
with itwith it
This was firstThis was first
demonstrated in thedemonstrated in the
1840s1840s Image fromImage from
glenbrook.k12.il.us/gbssciglenbrook.k12.il.us/gbssci
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Refraction (Bending) of LightRefraction (Bending) of Light
Ray A comes fromRay A comes from
straight up andstraight up and
does not benddoes not bend
muchmuch Ray B comes at aRay B comes at a
shallow angle andshallow angle and
bends a lot morebends a lot more Image from seafriends.org.nzImage from seafriends.org.nz
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The View From UnderwaterThe View From Underwater
Underwater, the light always shines downUnderwater, the light always shines downsteeply, even when the Sun is low in thesteeply, even when the Sun is low in the
skysky
The whole sky appears in a limited roundThe whole sky appears in a limited round
area called Snells Windowarea called Snells Window Image from seafriends.org.nzImage from seafriends.org.nz
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Light Coming Out of WaterLight Coming Out of Water
Animation on link Ch 1bAnimation on link Ch 1b http://www.phy.ntnu.edu.tw/ntnujava/viewtopic.php?t=66http://www.phy.ntnu.edu.tw/ntnujava/viewtopic.php?t=66
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Total Internal ReflectionTotal Internal Reflection
There is a critical angle atThere is a critical angle atwhich no light can bewhich no light can berefracted at all, so 100% ofrefracted at all, so 100% of
the light is reflectedthe light is reflected Light is trapped in the waterLight is trapped in the water
and cannot escape into theand cannot escape into theairair
This works with any denseThis works with any densemedium, such as plastic ormedium, such as plastic orglass, the same way it worksglass, the same way it workswith waterwith water Image fromImage from glenbrook.k12.il.usglenbrook.k12.il.us
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How Light Travels in FiberHow Light Travels in Fiber
Image from ece.umd.edu/~davisImage from ece.umd.edu/~davis
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Bare FiberBare Fiber
During 1920-1950,During 1920-1950,
thin, flexible rods ofthin, flexible rods of
glass or plasticglass or plastic
were used to guidewere used to guidelightlight
Such bare fibersSuch bare fibers
require air outsiderequire air outsideeach fibereach fiber Image from WikipediaImage from Wikipedia
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Fiber With CladdingFiber With Cladding
Developed in 1954Developed in 1954by van Heel, Hopkinsby van Heel, Hopkins& Kapany& Kapany
Cladding is a glass orCladding is a glass or
plastic cover aroundplastic cover aroundthe corethe core
Protects the total-Protects the total-reflection surfacereflection surface
contaminationcontamination Reduces cross-talkReduces cross-talk
from fibers infrom fibers inbundlesbundles
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Medical ImagingMedical Imaging
By 1960, glass-clad fibers wereBy 1960, glass-clad fibers were
available for medical instruments, toavailable for medical instruments, to
look inside the bodylook inside the body
The glass was unable to transmitThe glass was unable to transmit
light far enough for communications,light far enough for communications,
because of impuritiesbecause of impurities
Attenuation (loss of light) was 1 decibelAttenuation (loss of light) was 1 decibel
per meterper meter
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DecibelsDecibels
Decibels are a logarithmic scale of powerDecibels are a logarithmic scale of power
Abbreviated dBAbbreviated dB
A loss of 10 decibels means only 10% ofA loss of 10 decibels means only 10% of
the light gets throughthe light gets through A loss of 20 dB means 1% of the light getsA loss of 20 dB means 1% of the light gets
throughthrough
Sunglasses stop 99% of light, so they cause aSunglasses stop 99% of light, so they cause aloss of 20 dBloss of 20 dB
For communications, loss must be noFor communications, loss must be no
more than 10 or 20 decibels per kilometermore than 10 or 20 decibels per kilometer
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Optical Fiber in 1966Optical Fiber in 1966
Charles Kao developed a fiber thatCharles Kao developed a fiber that
could transmit 1 GHz (One billion bitscould transmit 1 GHz (One billion bits
per second)per second)
But attenuation was 1000 dB/km, soBut attenuation was 1000 dB/km, so
it could not transmit light far enoughit could not transmit light far enough
for practical communicationsfor practical communications
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CorningCorning
Corning scientists developed low-Corning scientists developed low-
attenuation silica glass fibers in 1970attenuation silica glass fibers in 1970
Corning Video: At The Speed of LightCorning Video: At The Speed of Light
Link Ch 1c on my Web pageLink Ch 1c on my Web page
(samsclass.info)(samsclass.info)
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Singlemode and Multimode FiberSinglemode and Multimode Fiber
Singlemode fiber has a core diameterSinglemode fiber has a core diameter
of 8 to 9 micronsof 8 to 9 microns
Multimode fiber has a core diameterMultimode fiber has a core diameter
of 50 or 62.5 micronsof 50 or 62.5 microns
Both have a cladding diameter ofBoth have a cladding diameter of
125 microns125 microns
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Optical Fiber in 1977Optical Fiber in 1977
Telephone signals used infrared lightTelephone signals used infrared lightwith a wavelength of 850 nm to sendwith a wavelength of 850 nm to senddata at 6.2 Mbps and 45 Mbpsdata at 6.2 Mbps and 45 Mbps
Loss was 2 dB per kmLoss was 2 dB per km Repeaters were required every fewRepeaters were required every few
kilometerskilometers
The repeaters were electro-optical The repeaters were electro-optical converting the light to electricity andconverting the light to electricity andthen back to lightthen back to light
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TAT-8TAT-8
In 1988 AT&T laid theIn 1988 AT&T laid thefirst fiber-opticfirst fiber-optictransatlantic telephonytransatlantic telephonycablecable
3,148 miles long3,148 miles long Connected NorthConnected North
America to FranceAmerica to France Repeaters every 40Repeaters every 40
milesmiles 565 Mbps bandwidth565 Mbps bandwidth Used 1300 nm lightUsed 1300 nm light Attenuation 0.4 dB/kmAttenuation 0.4 dB/km
Image from att.comImage from att.com
Info from link Ch 1eInfo from link Ch 1e www.greatachievements.orgwww.greatachievements.org/?id=3706/?id=3706
http://www.greatachievements.org/?id=3706http://www.greatachievements.org/?id=3706http://www.greatachievements.org/?id=3706http://www.greatachievements.org/?id=3706http://www.greatachievements.org/?id=3706http://www.greatachievements.org/?id=3706 -
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Fiber AmplifierFiber Amplifier
Special fiber with Erbium atoms in it isSpecial fiber with Erbium atoms in it is
used to amplify light without changing it toused to amplify light without changing it to
an electrical signal firstan electrical signal first
Uses stimulated emission, the sameUses stimulated emission, the sameprinciple that makes lasers workprinciple that makes lasers work Image from rp-photonics.com (Link Ch 1g)Image from rp-photonics.com (Link Ch 1g)
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Wavelength Division MultiplexingWavelength Division Multiplexing
(WDM)(WDM)
Several signals can be sent throughSeveral signals can be sent through
the same fiber simultaneously bythe same fiber simultaneously by
using different wavelengths (colors)using different wavelengths (colors)
of lightof light That means more bandwidthmoreThat means more bandwidthmore
data per seconddata per second
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Freeway AnalogyFreeway Analogy
TAT-8 in 1980TAT-8 in 1980 565 Mbps565 Mbps
Electro-opticalElectro-opticalrepeatersrepeaters
TAT-12/13 in 1996TAT-12/13 in 1996 2.5 Gbps2.5 Gbps
Optical amplifiersOptical amplifiers
19981998
20 Gbps20 Gbps WDM with 8WDM with 8
wavelengthswavelengths Image from www2.rad.comImage from www2.rad.com
(Link Ch 1j)(Link Ch 1j)
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Dense Wavelength DivisionDense Wavelength Division
Multiplexing (DWDM)Multiplexing (DWDM)
Uses up to 100 wavelengths throughUses up to 100 wavelengths through
a single fibera single fiber
Bandwidth up to 1 Tbps (1000 Gbps)Bandwidth up to 1 Tbps (1000 Gbps)
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Lennie Lightwave'sLennie Lightwave's
Guide To Fiber OpticsGuide To Fiber Optics
BasicsBasicsFrom jimhayes.com/lennielwFrom jimhayes.com/lennielw
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Fiber Optics HistoryFiber Optics History
Fiber optics began about 30 yearsFiber optics began about 30 years
ago in the R&D labs (Corning, Bellago in the R&D labs (Corning, Bell
Labs, ITT UK, etc.)Labs, ITT UK, etc.)
First installed in Chicago in 1976First installed in Chicago in 1976
By the early 1980s, fiber networksBy the early 1980s, fiber networks
connected the major cities on eachconnected the major cities on each
coast.coast.
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The 1980sThe 1980s
By the mid-80s, fiber was replacingBy the mid-80s, fiber was replacingall the telco copper, microwave andall the telco copper, microwave andsatellite linkssatellite links
In the 90s, CATV started using fiberIn the 90s, CATV started using fiberto enhance the reliability of theirto enhance the reliability of theirnetworksnetworks
CATV companies also discovered theyCATV companies also discovered theycould offer phone and Internet servicecould offer phone and Internet serviceon that same fiber and greatly enlargedon that same fiber and greatly enlargedtheir marketstheir markets
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Computers and LANsComputers and LANs
Started using fiber about the sameStarted using fiber about the sametime as the telcostime as the telcos
Industrial links were among the firstIndustrial links were among the first
as the noise immunity of fiber and itsas the noise immunity of fiber and itsdistance capability make it ideal fordistance capability make it ideal forthe factory floorthe factory floor
Mainframe storage networks cameMainframe storage networks camenext, the predecessors of today'snext, the predecessors of today'sfiber SANs (storage area networks.)fiber SANs (storage area networks.)
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Other ApplicationsOther Applications
Aircraft, ship and automobile dataAircraft, ship and automobile data
busesbuses
CCTV for securityCCTV for security
Links for consumer digital stereoLinks for consumer digital stereo
Today fiber optics is either theToday fiber optics is either the
dominant medium or a logical choicedominant medium or a logical choicefor every communication systemfor every communication system
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Which Fiber Optics?Which Fiber Optics?
"Outside Plant" fiber optics are used"Outside Plant" fiber optics are used
in telephone networks or CATVin telephone networks or CATV
"Premises" fiber optics are usedin"Premises" fiber optics are usedin
buildings and campusesbuildings and campuses
Just like "wire" which can mean lotsJust like "wire" which can mean lots
of different things - power, security,of different things - power, security,
HVAC, CCTV, LAN or telephone -HVAC, CCTV, LAN or telephone -
fiber optics is not all the same.fiber optics is not all the same.
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Installing Fiber OpticsInstalling Fiber Optics
Fiber is harder to install than 100 MbpsFiber is harder to install than 100 Mbpscopper Ethernet cablecopper Ethernet cable
But fiber is MUCH faster, so theBut fiber is MUCH faster, so theinfrastructure wont need to be upgradedinfrastructure wont need to be upgradedso soonso soon And gigabit Ethernet is harder to installAnd gigabit Ethernet is harder to install
LAN copper cable is delicate. It only has aLAN copper cable is delicate. It only has a
25 pound pulling tension limit and kinks25 pound pulling tension limit and kinkswill ruin the high speed performancewill ruin the high speed performance Fiber has more strength and greater toleranceFiber has more strength and greater tolerance
to abuse than copper wireto abuse than copper wire
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Safety First!Safety First!
The light in the fiber can burn yourThe light in the fiber can burn your
retinaretina
NEVER look into a fiber unless youNEVER look into a fiber unless you
know no light is present - use aknow no light is present - use a
power meter to check itpower meter to check it
The infrared light is invisibleThe infrared light is invisible
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Fiber ShardsFiber Shards
When you cleave fiber, there areWhen you cleave fiber, there are
small scraps of glass produced.small scraps of glass produced.
These scraps are very dangerous!These scraps are very dangerous!
The cleaved ends are extremelyThe cleaved ends are extremely
sharp and can easily penetrate yoursharp and can easily penetrate your
skinskin
They are even worse in your eyes,They are even worse in your eyes,
mouth, etc.mouth, etc.
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Safety RulesSafety Rules
Wear glasses or safety glassesWear glasses or safety glasses Dispose of all scraps properly:Dispose of all scraps properly:
Put scraps on black tapePut scraps on black tape
Use a properly marked trashcanUse a properly marked trashcan Work on a black pad which makesWork on a black pad which makes
the slivers of glass easier to spotthe slivers of glass easier to spot
Do not drop scraps on the floorDo not drop scraps on the floor Do not eat or drink anywhere nearDo not eat or drink anywhere near
the work areathe work area
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Chemical SafetyChemical Safety
Fiber optic splicing and terminationFiber optic splicing and termination
use various chemical adhesives anduse various chemical adhesives and
cleanerscleaners
Follow the instructions for useFollow the instructions for use
carefullycarefully
Isopropyl alcohol, used as a cleaner,Isopropyl alcohol, used as a cleaner,
is flammableis flammable
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Zero Tolerance for DirtZero Tolerance for Dirt
Airborne particles are about the sizeAirborne particles are about the size
of the core of Single Mode fiberof the core of Single Mode fiber
They absorb lots of light and mayThey absorb lots of light and may
scratch connectors if not removedscratch connectors if not removed
Dirt on connectors is the biggest causeDirt on connectors is the biggest cause
of scratches on polished connectors andof scratches on polished connectors and
high loss measurementshigh loss measurements
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Hygiene RulesHygiene Rules
Work in a clean area avoid dustWork in a clean area avoid dust
Keep dust caps on all connectorsKeep dust caps on all connectors
Use lint free pads and isopropylUse lint free pads and isopropylalcohol to clean connectorsalcohol to clean connectors