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 Fiber Optics Technology

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 I ntroduction to Optical Fibers.

Fibers of glass

Usually 120 micrometers in diameterUsed to carry signals in the form of light over distances up to 50 km.

No repeaters needed.

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 I ntroduction (Cont«)

Core thin glass center of the fiber

where light travels.Cladding outer optical materialsurrounding the core

Buffer Coating

plasticcoating that protects

the fiber.

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 Evolution of Fiber 1880   A lexander Graham Bell

1930   Patents on tubing

1950   Patent for two-layer glass wave-guide1960   Laser first used as light source

1965   High loss of light discovered

1970s  R

efining of manufacturing process1980s   OF technology becomes backbone of long distance telephone networks in N A .

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 Ad vantages of Optical Fibre

Thinner

Less ExpensiveHigher Carrying Capacity

Less Signal Degradation& Digital Signals

Light Signals

Non-Flammable

Light Weight 

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 Areas of  A pplication

Telecommunications

Local  A rea Networks

Cable TV

CCTV

Optical Fiber Sensors

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Type of FibersOptical fibers come in two types:

Single-mode fibers used to transmit one signal

per fiber (used in telephone and cable TV). Theyhave small cores(9 microns in diameter) andtransmit infra-red light from laser.

Multi-mode fibers used to transmit manysignals per fiber (used in computer networks). Theyhave larger cores(62.5 microns in diameter) andtransmit infra-red light from LED.

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 H ow Does Optical FibreTransmit Light??Total Internal Reflection.

Fibre Optics Relay Systems has-Transmitter

-Optical Fibre

-Optical Regenerator-Optical Receiver

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 P roperties of optical fibersFiber has to have two important properties:Total internal reflection, so that light is containedwithin fiberLow attenuation, so that light can be carried over

long distances with minimal lossStructure

Inner core glass: high refractive index (contains light )Cladding glass: lower refractive indexO

uter polymer coating: adds strength & protects fiber

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Light ray must enter the fiber within a certain acceptance angle. If not, light will get refracted out as condition for total internalreflection will be violated; this becomes important when a fiberbendsThe way to avoid losing light is to make fibers with small diameters;thinner fibers also better from a flexibility and weight point of view

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Total  I nternal Reflection in Fiber 

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SEEFIRE workshop ± 

Sofia, 14-15 July 2005

12

 Fiber Types

Multi-Mode: supports

hundreds paths for light.

Single-Mode: supports asingle path for light 

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SEEFIRE workshop ± Sofia, 14-15 July 2005 13

 Attenuation

It is the reduction of light power over the length of the fiber.

Its mainly caused by scattering.

It depends on the transmission frequency.

Its measured in dB/km ( ))(log10 10 inout dB !

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 H ow are Optical Fibre¶s made??

Three Steps are Involved

-Making a Preform Glass Cylinder-Drawing the Fibres from the preform

-Testing the Fibre

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Testing of Optical Fiber 

Tensile Strength

Refractive Index ProfileFiber Geometry

Information Carrying Capacity

Operating temperature/humidity range A bility to conduct light under water

 A ttenuation

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Optical Fiber Laying Mechanical Linking

Includes coupling of two connectors end to end

Optical distribution frames allow cross connect fibersfrom by means of connection leads and opticalconnectors

Soldering: This operation is done with automatic soldering machine that 

ensures:  A lignment of fibers core along the 3 axis

  Visual display in real-time of the fibers soldering

  Traction test after soldering (50 g to 500 g)

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Optical Fiber Laying (Cont«)

Blowing

Used in laying optical cables in roadways.Cables can be blown in a tube high densityPoly Ethylene

Optical fiber is then blown in the tube

using an air compressor which can propel it up to 2 kilometers away.

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Tools of TradeCleaning fluid and rags

Buffer tube cutter

Reagent-grade isopropyl alcohol

Canned air

Tape (masking or scotch)

Coating strip

Microscope or cleaver checkerSplicer

Connector supplies

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 Fiber Optics Test Kit Features

Includes Smart FO Power Meter and Mini LED orlaser source

FO test lite software for data logging

Tests all networks and cable plants

New versions of Gigabit Ethernet 

Low Cost 

 A pplications

Measure optical power or loss

Trouble shooting networks

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 P rotecting FibersTougher than copper wires

Designed in three concentric layers

Core   Cladding   Buffer

Two basic buffer types

Tight buffer Loose tubes

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 I mplementation of Different L

 AN  s

IEEE 802.3

FOIRL Fiber optic inter repeater link

Defines remote repeaters using fiber optics

Maximum length   1000 meters between any two

repeaters.

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 IEEE 802.3 (Cont«)10B A SEF Star topology with hub in the center

Passive hub:

  Short cables  No cascading

  Reliable

A ctive hum:

  Synchronous May be cascaded

  Do not count as one repeater

  A ny 10B A SEF active hub must have at least two FOIRL ports

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Token Ring (Cont«)Disadvantages

Relatively expensive cable cost and installation cost 

Requires specialist knowledge and test equipment 

No IEEE 802.5 standard published yet 

Relatively small installed base.

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 Fiber Distributed Data  I nterface

Stations are connected in a dual ring

Transmission rate is 100 mbps

Total ring length up to 100s of kms.

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ConclusionThis concludes our study of Fiber Optics. We have

looked at how they work and how they are made. We have

examined the properties of fibers, and how fibers are

 joined together. Although this presentation does notcover all the aspects of optical fiber work it will have

equipped you knowledge and skills essential to the fiber 

optic industry.