Fiber Optic Communications

TE-504Department of TE&CE IIU

IslamabdInstructor :Engr. Muhammad Ashraf

Bhutta

Lecture 1 - outline

• Course info• Fiber optic introduction• fiber basics• history• modulation formats• digital/analog modulation• ray optics description of fibers• Relevant chapters in the book:1-2.1

Course outline

• week.1 Introduction, Optical fibers - geometrical description

• week.2Optical fibers - waveguiding, Maxwells equations

• week 3 Optical fibers - dispersion, pulse broadening, attenuation

• week 4 Optical fibers - nonlinearities • Week 5 Solitons, nonlinear phenomena • week 6 Light emitting diodes, semiconductor

lasers

Course outline…

• week 7 Photodetectors, receivers • Week 8 Optical amplifiers • Week 9 Optical amplifiers • Week 10 Receiver performance • Week 11 System design • Week 12 Dispersion compensation • Week 13 Multi-channel systems, WDM / OTDM • Week 14 Coherent systems, Microwave

Photonics• NOTE: Each week we,ll have two

lectures(02hrs+01hrs)

Home assignment, Research

papers• 4 Assignments• Three quizez• Two research Papers on the topics covered in the course• Text books• Fiber Optic Communications Technology 3rd edition By

Djafar K. • Optical fiber communications Third edition by Gerd

Keiser• Fiber Optic Communication systems Third Edition by

Govind p. Agrawal

A definition of Fiber Optics

• Utilization of electromagnetic waves in dielectric, circular waveguides combined with optoelectronic devices (LEDs, lasers, photodiodes, amplifiers, etc.)

• Applications of fiber optics:• communication• medical applications• optical sensing• power distribution• welding, drilling...

Some definitions

• Visible spectrum 0.4 to 0.7 micrometer

• Optical (guided light) communication field 700-1600 nm

• Reflection and refraction

• refractive index n=c/v

• Dispersion: process of separating light into each of its component frequencies.

• Diffraction:bending of light as it passes through an openong in an obstacle

• Absorption:conversion of light into heat• Amount of energy contained in light is

determined by wavelength or frequency• E=hf(joules per photon)• Light passing from a lower refractive index

to a higher one is bent toward the normal

Fresnel reflection

• Independentof the index of the two media , a small portion of light will always be reflected when light passes from one index to another ,this is called fresnel reflecton(p)

• P=(n-1/n+1)2

• dB=10log10(1-p)

The electromagnetic spectrum

Fiber Optic Commnication Link

Optical Fibers

A multi-disciplinary technology

Undersea systems

Fiber basics

Optical Fibers

Fiber advantages

• Low attenuation (0.2 dB/km)• Large bandwidth (35 THz)• Wavelength independent attenuation in

the transmission window• The enormous capacity of an installed

fiber can be utilized in future as the demand increases

• Small geometry and low weight• Flexible• Easy to install•

Fiber advantages……

• Low sensitivity to moisture• The fiber endpoints handle large

differences in voltage• Immune to electromagnetic interference• No crosstalk between fibers• Damage can not cause sparking• Potentially low cost• Well suited for future broadband

services

WDM-OTDM

Progress in Lightwave communication (2)

Direct detection digital and analog systems

Analog and digital signals

The dB units

Fiber types

Ray-optics description of step-index fiber (1)

Numerical apereture