Total Internal Reflection

Refraction (Bending) of Light Sunlight shines down into the water Sunlight shines down into the water Ray A comes from straight up into the water and does not bend much Ray A comes from straight up into the water and does not bend much Ray B comes at a shallow angle and bends a lot more Ray B comes at a shallow angle and bends a lot more Image from seafriends.org.nzImage from seafriends.org.nz

The View From Underwater Underwater, the light always shines down steeply, even when the Sun is low in the sky Underwater, the light always shines down steeply, even when the Sun is low in the sky The whole sky appears in a limited round area called “Snells Window” The whole sky appears in a limited round area called “Snells Window” Image from seafriends.org.nzImage from seafriends.org.nz

Light is Trapped Underwater The light ray that comes from the fish to the origin cannot escape the water The light ray that comes from the fish to the origin cannot escape the water Total Internal Reflection Total Internal Reflection

Guiding Light With Water Light in a stream of water stays inside the water and bends with it Light in a stream of water stays inside the water and bends with it This was first demonstrated in the 1840s This was first demonstrated in the 1840s Image from glenbrook.k12.il.us/gbssciImage from glenbrook.k12.il.us/gbssci

Total Internal Reflection There is a critical angle at which no light can be refracted at all, so 100% of the light is reflected There is a critical angle at which no light can be refracted at all, so 100% of the light is reflected Light is trapped in the water and cannot escape into the airLight is trapped in the water and cannot escape into the air This works with any dense medium, such as plastic or glass, the same way it works with waterThis works with any dense medium, such as plastic or glass, the same way it works with water Image from glenbrook.k12.il.us Image from glenbrook.k12.il.us

Types of Optical Fiber

Bare Fiber During , thin, flexible rods of glass or plastic were used to guide light During , thin, flexible rods of glass or plastic were used to guide light Such “bare” fibers require air outside each fiber Such “bare” fibers require air outside each fiber Fibers degrade rapidly from handling Fibers degrade rapidly from handling Image from WikipediaImage from Wikipedia

Fiber With Cladding Developed in 1954 by van Heel, Hopkins & Kapany Developed in 1954 by van Heel, Hopkins & Kapany Cladding is a glass or plastic cover around the core Cladding is a glass or plastic cover around the core Protects the total- reflection surface from contamination Protects the total- reflection surface from contamination Reduces cross-talk from fibers in bundles Reduces cross-talk from fibers in bundles

Corning Corning scientists developed low- attenuation silica glass fibers in 1970 Corning scientists developed low- attenuation silica glass fibers in 1970 Corning Video: At The Speed of Light Corning Video: At The Speed of Light Link Ch 1c on my Web page (samsclass.info, CNIT 211 / ELEC 211)Link Ch 1c on my Web page (samsclass.info, CNIT 211 / ELEC 211)

Singlemode and Multimode Fiber Singlemode fiber has a core diameter of 8 to 9 microns Singlemode fiber has a core diameter of 8 to 9 microns Multimode fiber has a core diameter of 50 or 62.5 microns Multimode fiber has a core diameter of 50 or 62.5 microns Both have a cladding diameter of 125 microns Both have a cladding diameter of 125 microns

Singlemode Fiber Singlemode fiber has a core diameter of 8 to 9 microns, which only allows one light path or mode Singlemode fiber has a core diameter of 8 to 9 microns, which only allows one light path or mode Images from arcelect.com (Link Ch 2a)Images from arcelect.com (Link Ch 2a) Index of refraction

Multimode Step-Index Fiber Multimode fiber has a core diameter of 50 or 62.5 microns (sometimes even larger) Multimode fiber has a core diameter of 50 or 62.5 microns (sometimes even larger) Allows several light paths or modesAllows several light paths or modes This causes modal dispersion – some modes take longer to pass through the fiber than others because they travel a longer distanceThis causes modal dispersion – some modes take longer to pass through the fiber than others because they travel a longer distance See animation at link Ch 2fSee animation at link Ch 2f Index of refraction

Multimode Graded-Index Fiber The index of refraction gradually changes across the core The index of refraction gradually changes across the core Modes that travel further also move fasterModes that travel further also move faster This reduces modal dispersion so the bandwidth is greatly increasedThis reduces modal dispersion so the bandwidth is greatly increased Index of refraction

Popular Fiber Types At first there were only two common types of fiber At first there were only two common types of fiber 62.5 micron multimode, intended for LEDs and 100 Mbps networks62.5 micron multimode, intended for LEDs and 100 Mbps networks There is a large installed base of 62.5 micron fiber There is a large installed base of 62.5 micron fiber 8 micron single-mode for long distances or high bandwidths, requiring laser sources8 micron single-mode for long distances or high bandwidths, requiring laser sources Corning’s SMF-28 fiber is the largest base of installed fiber in the world (links Ch 2j, 2k) Corning’s SMF-28 fiber is the largest base of installed fiber in the world (links Ch 2j, 2k)

Gigabit Ethernet 62.5 micron multimode fiber did not have enough bandwidth for Gigabit Ethernet (1000 Mbps) 62.5 micron multimode fiber did not have enough bandwidth for Gigabit Ethernet (1000 Mbps) LEDs cannot be used as sources for Gigabit Ethernet – they are too slow LEDs cannot be used as sources for Gigabit Ethernet – they are too slow So Gigabit Ethernet used a new, inexpensive source: So Gigabit Ethernet used a new, inexpensive source: Vertical Cavity Surface Emitting Laser (VCSEL)

LEDs and VCSELs From led_laser.htm From led_laser.htm

Multimode Fiber Designed for VCSELs First came laser-rated 50 micron multimode First came laser-rated 50 micron multimode Bandwidth 500 MHz-km at 850 nmBandwidth 500 MHz-km at 850 nm Then came laser-optimized 50 micron multimode Then came laser-optimized 50 micron multimode Bandwidth 2000 MHz-km at 850 nmBandwidth 2000 MHz-km at 850 nm Distinctive aqua-colored jacketDistinctive aqua-colored jacket See links Ch 2g, 2h, 2i See links Ch 2g, 2h, 2i

Cable Types

Loose-Tube Cable Used Outdoor Used Outdoor Ducts or conduitsDucts or conduits Aerial lashedAerial lashed Directly buried (armored)Directly buried (armored) Weather-resistant Weather-resistant From alphawire.com (link Ch 4k)From alphawire.com (link Ch 4k)

Tight-Buffer Cable PVC Buffer is extruded directly onto the coating PVC Buffer is extruded directly onto the coating Diameter is 900 micronsDiameter is 900 microns Makes cable more flexibleMakes cable more flexible Easier to terminateEasier to terminate The most common indoor cable typeThe most common indoor cable type Not good for outside useNot good for outside use Because the buffer strains the fiber as temperature fluctuates, increasing attenuation Because the buffer strains the fiber as temperature fluctuates, increasing attenuation Image from mohawk-cdt.com (link Ch 4f) Image from mohawk-cdt.com (link Ch 4f)

Distribution Cables Distribution Cable Distribution Cable Several tight-buffer fibersSeveral tight-buffer fibers Kevlar reinforcement (Aramid)Kevlar reinforcement (Aramid) One jacketOne jacket Image from arcelect.com (link Ch 4g) Image from arcelect.com (link Ch 4g)

Distribution Cable Contains tight-buffered fibers in bundles of up to 12 each Contains tight-buffered fibers in bundles of up to 12 each Used for Riser and Office Cabling Used for Riser and Office Cabling Must be terminated inside a patch panel or junction box Must be terminated inside a patch panel or junction box From alphawire.com (link Ch 4i)From alphawire.com (link Ch 4i)

Breakout Cables Breakout Cable Breakout Cable Reinforce each tight-buffer fiber with Kevlar and jacket itReinforce each tight-buffer fiber with Kevlar and jacket it Each fiber can be broken out and individually connectorizedEach fiber can be broken out and individually connectorized Image from arcelect.com (link Ch 4g) Image from arcelect.com (link Ch 4g)

Ribbon cable Dozens of fibers packed together Dozens of fibers packed together Can be mass fusion spliced or mass terminated Can be mass fusion spliced or mass terminated Images from gore.com (link Ch 4b) and alcatel.com (link Ch 4c) Images from gore.com (link Ch 4b) and alcatel.com (link Ch 4c)

Connectors and Splices

Connectors There are four types There are four types Rigid Ferrule (most common)Rigid Ferrule (most common) Resilient ferruleResilient ferrule Grooved plate hybridsGrooved plate hybrids Expanded beamExpanded beam Top image shows ferrules from swiss-jewel.com (link Ch 6e) Top image shows ferrules from swiss-jewel.com (link Ch 6e) Lower image shows LC, SC, Biconic, and the obsolete Deutsch 1000 Lower image shows LC, SC, Biconic, and the obsolete Deutsch 1000 From thefoa.org (link Ch 6d)From thefoa.org (link Ch 6d)

Rigid Ferrule Connectors 2.5 mm ferrule 2.5 mm ferrule ST ST SC SC FC FC Images from thefoa.org (link Ch 6d) Images from thefoa.org (link Ch 6d)

Rigid Ferrule Connectors 1.25 mm ferrule 1.25 mm ferrule Small Form Factor Small Form Factor LC LC MU MU LX-5 LX-5 Images from thefoa.org (link Ch 6d) Images from thefoa.org (link Ch 6d)

Fusion Splicing Melts the fibers together to form a continuous fiber Melts the fibers together to form a continuous fiber Expensive machine Expensive machine Strongest and best join for singlemode fiber Strongest and best join for singlemode fiber May lower bandwidth of multimode fiberMay lower bandwidth of multimode fiber

Mass Fusion Splicing Video from fitel.fiberoptic.com (link Ch 6i) Video from fitel.fiberoptic.com (link Ch 6i)

Mechanical Splicing Mechanically aligns fibers Mechanically aligns fibers Contains index-matching gel to transmit light Contains index-matching gel to transmit light Equipment cost is low Equipment cost is low Per-splice cost is high Per-splice cost is high Quality of splice varies, but better than connectors Quality of splice varies, but better than connectors Fiber alignment can be tuned using a Visual Fault Locator Fiber alignment can be tuned using a Visual Fault Locator

OTDR: Testing Cable Plants

OTDR Optical Time-Domain Reflectometer Image from exfo.com Image from exfo.com

OTDR Uses Measure loss Measure loss Locate breaks, splices, and connectors Locate breaks, splices, and connectors Produces graphic display of fiber status Produces graphic display of fiber status Can be stored for documentation and later referenceCan be stored for documentation and later reference Cable can be measured from one end Cable can be measured from one end

Backscatter A small amount of light is scattered back to the source from the fiber itself A small amount of light is scattered back to the source from the fiber itself Splices or connector pairs cause a larger reflection of light back to the source Splices or connector pairs cause a larger reflection of light back to the source Figure from techoptics.com (link Ch 17a)Figure from techoptics.com (link Ch 17a)

OTDR Display Dead zone

OTDR Trace of CCSF Fiber Loop Total length: 66 km Total length: 66 km Start of cable Connection Points End of cable

The Future of Fiber Optics Faster Networks

History of Ethernet From Corning (link Ch 5b) From Corning (link Ch 5b)

Sources

Bandwidth Comparison Multimode Fiber is limited to 10 Gbps for reasonable lengths (30 m) Multimode Fiber is limited to 10 Gbps for reasonable lengths (30 m) Singlemode Fiber is MUCH faster – its bandwidth is estimated to be 100,000 Gbps (100 Tbps) Singlemode Fiber is MUCH faster – its bandwidth is estimated to be 100,000 Gbps (100 Tbps) But no electronics are available yet to transmit signals that fastBut no electronics are available yet to transmit signals that fast From

Singlemode Fiber is NOT Expensive Price of 500 feet of riser-rated indoor bulk cable, 12-fiber Price of 500 feet of riser-rated indoor bulk cable, 12-fiber 62.5/125 micron MM$ /125 micron MM$889 50/125 micron MM $88950/125 micron MM $889 50/125 micron laser-optimized MM $114350/125 micron laser-optimized MM $ /125 micron SM$5848.5/125 micron SM$584 From blackbox.com (link Ch 5c) From blackbox.com (link Ch 5c)

Faster Electronics ARE More Expensive Price of electronic-to-optical media converters Price of electronic-to-optical media converters 100 Mbps Multimode:$ Mbps Multimode:$ Gbps Multimode:$ 7601 Gbps Multimode:$ Gbps Singlemode:$1,1801 Gbps Singlemode:$1,180 Prices from L-Com.com (Links Ch 5d & 5e) Prices from L-Com.com (Links Ch 5d & 5e)

Fiber to the Home One fiber cable can carry voice, data, and video One fiber cable can carry voice, data, and video Already available in many cities Already available in many cities about_installation.asphttp://www22.verizon.com/FiOSForHome/channels/FiOS/root/ about_installation.asphttp://www22.verizon.com/FiOSForHome/channels/FiOS/root/ about_installation.asphttp://www22.verizon.com/FiOSForHome/channels/FiOS/root/ about_installation.asp

The Future of Fiber Optics More Secure Networks

Quantum Encryption Encryption keys are sent as individual photons Encryption keys are sent as individual photons Undetected spying is impossible, because measuring the photons changes themUndetected spying is impossible, because measuring the photons changes them europe.com/research/crl/QIG/securityfromeavesdropping.html europe.com/research/crl/QIG/securityfromeavesdropping.html europe.com/research/crl/QIG/securityfromeavesdropping.html europe.com/research/crl/QIG/securityfromeavesdropping.html

Commercial Quantum Key Distribution Devices MagiQ and Clavis MagiQ and Clavis

Sources Fiber Optic Technician's Manual, Third Edition by Jim Hayes Fiber Optic Technician's Manual, Third Edition by Jim Hayes City of Light : The Story of Fiber Optics (Sloan Technology Series) by Jeff Hecht City of Light : The Story of Fiber Optics (Sloan Technology Series) by Jeff Hecht Lennie Lightwave Guide To Fiber Optics Lennie Lightwave Guide To Fiber Optics