History of Optical Communication

? Hand signals, Flags and Smoke Signals

? Light Transmission through bent water jet

1000 Nature of light was defined and laws of reflection given

1880 Photo Phone by A.G. Bell

1962 Laser diode

1966 Idea of optical fiber for communication by Kao & Hock ham

1970 Chemical vapor deposition(VCD) < 20 db/ Km by Corning

1973 MCVD <1 db/Km by Bell Systems

1977 VAD < 0.4 db/Km @ 1300 nm by NTT & SEI

1980 Introduction of actual optical technology

1986 < 0.2 db/Km @ 1550 nm

1987 Photonic regenerators introduced

1988 British Telecom.

1990 O.F used in the long distance network

History of Optical Communication

Nature of Light and Laser

Nature of Light Short Wave

White Light

Coherent Light (Waves)

In-Coherent Light (Waves)

Laser

Stimulated Emission

Maximum Acceptance Angle on Optical Fiber

Frequency Spectrum

Radio Waves

Micro Waves

Infrared (Wave length > 0.7 micro meter)

Visible (0.4 (blue) to 0.7(red) micro meter)

Ultra Violet (< 0.4 micro meter)

Optical frequencies for Optical Fiber Transmission

Basic Optical Fiber System

TRANSMISSION CHARACTERISTICS OF OFC

Normalized Frequency Windows of Optical Fiber. Bandwidth Coupling Efficiency

Construction of single Fiber

Core

Cladding

Jacket

Types of Optical Fiber on profile

• Types with respect to Modes: Single Mode Fiber Multimode Fiber

• Types with respect to Index Profile: Step Index Graded Index

9

Fiber versus copper

Glass• Uses light

• Transparent

• Dielectric material nonconductive

• EMI immune

• Low thermal expansion

• Brittle, rigid material

• Chemically stable

Copper• Uses electricity

• Opaque

• Electrically conductive material

• Susceptible to EMI

• High thermal expansion

• Ductile material

• Subject to corrosion and galvanic reactions

10

Index of Refraction

It is the ratio of the speed of light through a medium to the speed of light through vacuum.

gIndex of refraction (n) = cV

V

11

Index of Refraction

It is equal to the sine of the angle of incidence divided by the sine of the angle of

refraction.

Index of refraction (n) = sin isin r

12

Refractive Indices

MATERIAL

VACCUM

AIR

MERCURY VAPOUR

WATER

GLASS

DIAMOND

INDEX OF REFRACTION

1.0000

1.0003

1.0009

1.3

1.6

2.4

Selected indices of refraction

Optical Fiber Transmission System

• Optical Transmitter:Produces and encodes the light signal.

• Optical Amplifier:May be necessary to boost the light signal (for long distance)

• Optical Receiver:Receives and decodes the light signal

• Optical Fiber:Conducts the light signal over a distance

Optical Transmitter

• Function:Electrical to optical converter

• Types:Light Emitting Diode (LED)

Laser Diode (LD)

• Comparison:Item LED LD

Data rate Low High

Mode Multimode Multimode/Single mode

Distance short long

Temp sensitivity

minor substantial

cost low expensive