Understanding Fiber Optics

Snell's LawSnell's Law

F. O. Communication SystemF. O. Communication System

Fiber Optics ConnectorsFiber Optics Connectors

Applications of F. O.Applications of F. O.

Multimode, Step-Index

Multimode, Graded-Index

Single mode

=n1 sin

sinn2

θ2

θ1

T h e a n g l e o f incidence φ and 1

refraction φ are 2

related to each other and to refractive indices of dielectrics by Snell's Law of Refraction which states that :

WDM Optical SystemWDM Optical SystemTotal Internal ReflectionTotal Internal Reflection

In 1870, , demonstrated that light used internal reflection to follow a specific path.? , in 1880, patented a method of light transfer called “piping light.”? developed an optical voice transmission system he called the photophone.?Fiber optic technology experienced a phenomenal rate of progress in the second half of the twentieth century.?

History History

Light Reflectedfrom surface

Light Gradually

Leaks OutWater

Flowing Out of Basin

Multimode Single mode

Cables

John Tyndall

William Wheeling

Alexander Graham Bell

The Arrival of Optical Revolution

10000

1000

100

10

1

0.1Year

Commercial System

Research Results

TDM CommericalWDM CommercialTDM ResearchWDM Research

1985 1990 1995 2000

Capa

city

/(GB/

s) WDM

Buffer

Core

Cladding

The simplest fiber optic cable consists of two concentric layers of transparent materials. The inner portion (the core) transports the light; the outer covering (the cladding) must have a lower refractive index than the core so the two are made of different materials.To provide mechanical protection for the cladding an additional plastic layer; the Primary Buffer is added. Some constructions of optic fiber have additional layers of buffer, which are then referred to as Secondary Buffer. It is very important to note that the whole fiber Core, Cladding & Primary Buffer is solid and the light is confined to the core by the Total Internal Reflection due to the difference in the refractive index of the core compared to that of cladding.

F.O. Cable ConstructionF.O. Cable Construction

Refractive Indexing MaterialRefractive Indexing Material

Transmitter Receiver

200 meters

Applications - Networks

Applications - Links

l l ll Telecom SONET ATM DWDM l l Fiber Amps CATVl lll AM vs FM vs Digital HFC LANs Ethernetl lll l Token Ring FDDI SANs ESCON Fiber Channel

l l l l Video Security Broadcast TV Industrial Linksl l l RS-232 RS-422 Wireless Antennasl l Utility grid management Sensors

∆ = 25 - 100 GHz(0.4 or 0.8 nm @ 1500 nm)

λ

Optical Fiber

40 - 120 km

Up to 10,000 km

R

R

R

R

Frequency-registeredtransmitters Receivers

WDMMux Amp Amp WDM

DeMux

λ1

λ2

λ3

λN

Numerical Aperture & Acceptance AngleNumerical Aperture & Acceptance Angle

N. A.= (n ) - (n )1 2

1975 : Coax, 274 Mb/s at 1km repeater spacing1980 : 0.8 um GaAs lasers, MMF, 45 Mb/s @10km1987 : 1.3 um InGaAsP lasers, SMF, 1.7 Gb/s @50km1990s : 1.55 um InGaAsP DFB lasers, SMF, 2.5-10 Gb/s @ 40km1990s : WDM, 1.55 um InGaAsP DFB lasers, EDFA, SMF,

2.5-10 Gb/s @ 300-10,000km repeater spacing2002 : 64 WDM chx 10Gbps over 250,000 km span

Lightwave EvolutionLightwave Evolution

Fastmedium(smallerindex ofrefraction)

θ1

θ2

SlowMedium

n1 n2

Low index n2

(Air)

High index n1

(Glass)Partial internalreflection

Incident ray

Exit ray

φ1

φ2

CladdingCore

Acceptance Angle

Acceptance Cone

Connector Insertion Loss Repeatability Fiber Type Applications

0.50-1.00 dB 0.20 dB SM, MM

0.20-0.70 dB 0.20 dB SM, MM

0.15 db (SM)0.10 dB (MM) 0.2 dB SM, MM

0.30-1.00 dB 0.25 dB SM, MM

0.20-0.45 dB 0.10 dB SM, MM

0.20-0.45 dB 0.10 dB SM, MM

FC

LC

SC

ST

SM, MM

Typ. 0.40 dB(SM)

Typ. 0.50 dB(MM)

Typ. 0.40 dB(SM)

Typ. 0.20 dB(MM)

Fiber OpticNetwork

High DensityInterconnection

High DensityInterconnection

Datacom

Datacom

Inter-/Intra-Building,

Security, Navy

Datacom,Telecommuni-

cations

FDDI

MT Array

SC Duplex

Sugar solution (80%)

StrengtheningFibersCore Cladding Coating

Cable Jacket

Vacuum 1.00000Air at STP 1.00029Ice 1.31Water at 20°C 1.33Acetone 1.36Ethyl alcohol 1.36Glycerine 1.473 1.49

Glass 1.5Sodium chloride 1.54Polystyrene 1.55Flint glasses 1.57-1.75Extra dense flint,EDF-3 1.7200 Diamond 2.417Sapphire 1.77

Output Input TransmitterOptical Comm.

ChannelOptical

Receiver

Transmitter Produces and encodes the light signals.

Optical Fiber Conducts the l ight s igna ls over a distance.

Optical Regenerator May be necessary to boost the light signal (for long distances).

l Format l Bandwidth l Protocol l Modulation l Characteristics l Power l Wavelength

l Loss l Dispersion l 4-Wave Mixing l Noisel Crosstalks l Distortion l Amplification

l Bandwidth l Responsivityl Sensitivity l Noise l Wavelength

Fiber is deployed at a rate of 2000 miles every hour.

Losses in F. O.Losses in F. O.1. Attenuation2. Material Absorption Losses 3. Linear Scattering Losses

a. Ray Leigh Scatter b. Mie Scattering4. Non Linear Scattering5. Micro Bending and Macro Bending 6. Dispersion

a. Intermodal Dispersion b. Intramodal Dispersion

F. O. ComponentsF. O. ComponentsTransmitterReceiver

ll- LEDs Laser Diodes l l- PIN Diodes APDs

lCableslConnectors lSplicesl Amplifiersl Hardware (Installation hardware, patch panels,

splice closures, conduit and innerduct, etc.)

Disadvantage of F. O.Disadvantage of F. O.?

The lack of standardization.?More difficult and expensive to splice than wires.?

Fiber optic components are expensive.

?and capacity.Lower signal attenuation (loss)?Immunity to Electrical Noise?Immune to noise ?(electromagnetic interference [EMI] and radio frequency interference [RFI]No crosstalk?Lower bit error rates?Signal Security?Difficult to tap?Nonconductive ?(does not radiate signals) Electrical IsolationNo common ground required?

Greatly increased bandwidth ?short circuit and sparks.Size and Weight?Environmental Protection?Resistant to radiation and ?corrosion.Resistant to temperature ?variations.Improved ruggedness and ?flexibility.Less restrictive in harsh ?environments.Overall System Economy?Low per-channel cost?Lower installation cost?

Freedom from

Advantages of F. O.Advantages of F. O.

62.5 / 125 microns

Core Cladding

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