Introduction to Introduction to Optical Fiber Optical Fiber

CommunicationCommunication

Optical Fiber CommunicationOptical Fiber Communication

Overview of SyllabusOverview of Syllabus• Why Optical Communication• Optical Fiber Structure

Wave guiding• Fiber types

Step IndexGraded Index

• Modes in Optical Fiber• Losses in Optical Fiber

Scattering lossAbsorption loss

• Fiber Materials and Properties

ReferenceReference1. Optical fiber communication-Keiser2. Introduction to fiber optics –Ajoy

Ghatak & K Thyagarajan3. Optical fiber communications-

J.M.Senior

PrerequisitesPrerequisites• Communication

MediumBaseband signal and modulation

• Analog and digitalSamplingDigitization

• Bandwidth and bitrate• TDM and FDM• Attenuation dB

CommunicationCommunicationInformation Source

Transmitter Receiver Information destination

Transmission channel

Message input to the transmitter

OrBase band

signal

Encoded or modulated

signal input to the channel

Weakened and distorted received

signal

Restored and decoded

message

Basic motivation behind new inventions in communication are1. Improve transmission fidelity2. Increase capacity or data rate of the channel3. Increase distance between amplification stations

Analog and digital signalAnalog and digital signal

Sampling, Quantization and codingSampling, Quantization and coding

Time domain and frequency domainTime domain and frequency domain

Bandwidth and Bit rateBandwidth and Bit rate

Frequency ranges in telecommunicationsFrequency ranges in telecommunications

1 GHz->

4 kHz

100 kHz

10 MHz

MessageBandwidth

Time Domain Multiplexing (TDM)Frequency Domain Multiplexing (FDM)

AttenuationAttenuation

Decibel or dB

A Short History of Optical A Short History of Optical TelecommunicationsTelecommunications

Circa 2500 B.C. Earliest known glassRoman times-glass drawn into fibersVenice Decorative Flowers made of glass fibers1609-Galileo uses optical telescope1626-Snell formulates law of refraction1668-Newton invents reflection telescope1840-Samuel Morse Invents Telegraph1870-Tyndall observes light guiding in a thin water jet1873-Maxwell electromagnetic waves1876-Elisha Gray and Alexander Bell Invent Telephone1877-First Telephone Exchange1880-Bell invents Photophone1888-Hertz Confirms EM waves and relation to light1880-1920 Glass rods used for illumination1897-Rayleigh analyzes waveguide1899-Marconi Radio Communication1902-Marconi invention of radio detector1910-1940 Vacuum Tubes invented and developed1930-Lamb experiments with silica fiber1936-1940 Communication using a waveguide light guiding in a thin water jet Photophone receiver

Photophone transmitter

A Short History- ContinuedA Short History- Continued1951-Heel, Hopkins, Kapany image transmission using fiber bundles1957-First Endoscope used in patient1958-Goubau et. al. Experiments with the lens guide1958-59 Kapany creates optical fiber with cladding1960-Ted Maiman demonstrates first laser in Ruby1960-Javan et. al. invents HeNe laser1962-4 Groups simultaneously make first semiconductor lasers1961-66 Kao, Snitzer et al conceive of low loss single mode fiber communications and develop theory1970-First room temp. CW semiconductor laser-Hayashi & PanishApril 1977-First fiber link with live telephone traffic-

GTE Long Beach 6 Mb/sMay 1977-First Bell system 45 mb/s links GaAs lasers 850nm Multimode -2dB/km lossEarly 1980s-InGaAsP 1.3 µm Lasers - 0.5 dB/km, lower dispersion-Single modeLate 1980s-Single mode transmission at 1.55 µm -0.2 dB/km1989-Erbium doped fiber amplifier1 Q 1996-8 Channel WDM4th Q 1996-16 Channel WDM1Q 1998-40 Channel WDM1998 Allwave fiber (Lucent Technologies)

Approaches to Optical Approaches to Optical CommunicationCommunication

Optical Fiber SystemOptical Fiber System