- This document provides an overview of an introductory lecture on optical communication. It defines key terms like light, photon, and electromagnetic radiation. It explains that light has both particle and wave properties. - The document outlines the evolution of optical communication technologies from early systems using sunlight or smoke signals to current fiber optic networks. It also discusses how innovations like lasers, optical fibers, amplifiers, and dense wavelength-division multiplexing have increased data rates and transmission distances over time. - The significance of optical communication systems is that they allow vastly higher bandwidth and lower transmission costs per bit compared to electrical networks.

1. ECC3601:
OPTICAL COMMUNICATION
Lecture 2: Introduction to Optical Communication
(Part 2)
Makhfudzah bt. Mokhtar, PhD.
Department of Computer and Communication Systems
Faculty of Engineering
University Putra Malaysia

2. LEARNING OUTCOMES
At the end of this lecture, students should be able to:
-Define ‘light’ and ‘photon’
-Explain the property of light in terms of particle
and wave
-Identify light as the information carrier signal
-Identify the significance of optical communication
-Follow the evolution of optical communication

3. What is Light?
Light
is an
electromagnetic radiation
that is responsible for
the sense of sight
Light
From Wikipedia, the free encyclopedia

4. Radiation can be defined as
small (subatomic) particles with kinetic energy that are radiated or
transmitted through space.
The behaviour of EMR depends on its wavelength. Higher frequencies
have shorter wavelengths, and lower frequencies have longer
wavelengths.
What is radiation?
Available at http://www.rerf.jp/general/whatis_e/index.html

5. What is Photon?
Light is transported by
particles, called photons.
They have no
mass, but carry
sizeable amount of energy.
About 1019 photons of a laser beam hit a mirror per
second. (© thn)
light and its particles: photons
Available at http://www.attoworld.de/Home/attoworld/ElectronsAndLight/LightAndPhotons/index.html

6. Light as a ‘particle’ and ‘wave’
Light has both wave and particle properties.
Electromagnetic radiation can be considered to consist of particle-like
packets of wave-energy called photons.
These massless particles travel at the speed of light (300,000 kilometers per
second in a vacuum).
Every photon is characterized by wavelength
(the distance from the crest of one wave to the
crest of the next wave), by frequency (the
number of wave cycles that pass by in a given
period, measured in Hertz, which stands for
cycles per second), and by the energy it carries
(measured in electron volts).
http://micro.magnet.fsu.edu/primer/java/wavebasics/index.html
Is light a particle or wave?
Available http://www.edinformatics.com/math_science/electromagnetic_spectrum.htm

7. The energy carried by a photon is proportional to the number of
field oscillations per second, called frequency.
The energy of infrared photons, which can build up a wave
oscillating at a low frequency relative to visible light is therefore
smaller than the energy of visible light photons.
The more photons cross a unit area per second the larger the
amplitude of oscillations of the electric and magnetic fields and the
higher the intensity of the light wave.
light and its particles: photons
Available at http://www.attoworld.de/Home/attoworld/ElectronsAndLight/LightAndPhotons/index.html

8. Preparation for Quiz 1
-Find equation than relates wavelength,
frequency and light speed (calculation based)
-Find equation that relates energy and
frequency of light (calculation based)

9. Light as information carrier signal
Sun’s radiation
Sender
Message
Receiver
Eye - brain
Hand motion,
semaphore line -Slow information transfer
-Limited transmission distance
(1790s)
-Higher probability of error
Sun’s radiation
Sender
Message
Receiver
Eye - brain
Smoke signal
-Longer transmission distance

10. Photophone
(1880)
Sender
Thin voicemodulated mirror
Sun’s radiation
Message-voice
-Not successfully
commercialized due to the
invention of telephone
Receiver
Photoconducting
selenium cell
Lamp
Sender
Blinker light,
traffic light
Message
Receiver
Eye - brain
-Low information capacity

11. (1960)
Unguided laser radiation
Sender
Laser
Modulated message
(non-fiber)
Receiver
Photodiode
-High capacity optic communication
-Need for clear line-of-sight
-Eye damage risk
(1960s)
Guided laser radiation
Sender
Laser
Modulated message
(Glass fiber)
Receiver
Photodiode
-Light beam is guided (based on John Tyndall demonstration – 1854)
-Very high attenuation, need for low attenuation of optical fiber

12. Evolution of optical fiber
Optical Fibre Communication – ppt
MeintSmit (OED)XaveerLeijtens (OED)Huug de Waardt (ECO)Eduward Tangdiongga (ECO)

13. The significance of optical communication system
Mbps
Increase of the bandwidth and decreases of the cost per
transmitted bit.
Ref.: S. Kartalopoulos, WDWM Networks, Devices and Technology
Introduction to Optical Communication – Lecture slide
Prof. Dr. Manoj Kumar

14. The significance of optical communication system
Increase of the bit rate distance
product BL for different
communication technologies over
time.
Ref.: G.P. Agrawal, Fiber-Optic Comm.
systems
A figure of merit of communication systems is the bit rate – distance product, BL,
where B is the bit rate and L is the repeater spacing.
Introduction to Optical Communication – Lecture slide
Prof. Dr. Manoj Kumar

15. Bit-rate distance product (BL) for different generations of optical communication systems.
Ref.: G.P. Agrawal, Fiber-Optic Comm. systems
* The increase of the capacity-distance product can be explained by
the four major innovations.
Introduction to Optical Communication – Lecture slide
Prof. Dr. Manoj Kumar

16. Evolution of lightwave system
1. Generation: The development of low-loss fibers (compared to glass
fiber) and semiconductor lasers (GaAs) in the 1970‘s.
A Gallium Arsenide (GaAs) laser operates at a wavelength of 0.8μm. The
optical communication systems allowed a bit rate of 45Mbit/s and repeater
spacing of 10km.
Example of a laser diode.
(Ref.: Infineon)
Introduction to Optical Communication – Lecture slide
Prof. Dr. Manoj Kumar

17. 2. Generation: The repeater spacing could be increased by
operating the lightwave system at 1.3μm. The attenuation of the
optical fiber drops from 2-3dB/km at 0.8μm down to 0.4dB/km at
1.3μm.
Silica fibers have a local minima at 1.3μm.
Introduction to Optical Communication – Lecture slide
Prof. Dr. Manoj Kumar

18. 2. Generation: The transition from 0.8μm to 1.3μm leads to the 2nd
Generation of lightwave systems. The bit rate- distance product can be
further increased by using single mode fibers instead of multi-mode fibers.
Single mode fibers have a distinctly lower dispersion than multi mode
fibers.
Lasers are needed which emit light at 1.3 μm.
3. Generation: Silica fibers have an absolute minima at 1.55μm. The
attenuation of a fiber is reduced to 0.2dB/km.
Dispersion at a wavelength of 1.55μm complicates the realization of
lightwave systems. The dispersion could be overcome by a dispersionshifted fibers and by the use of lasers, which operate only at single
longitudinal modes. A bit rate of 4Gbit/s over a distance of 100km was
transmitted in the mid 1980‘s.
Introduction to Optical Communication – Lecture slide
Prof. Dr. Manoj Kumar

19. 3. Generation: The major disadvantage of the 3. Generation optical
communication system is the fact that the signals are regenerated by
electrical means. The optical signal is transferred to an electrical signal
and the signal is regenerated and amplified before the signal is again
transferred to an optical fiber.
Traditional long distance single channel fiber transmission system.
Ref.: H. J.R. Dutton, Understanding optical communications
Introduction to Optical Communication – Lecture slide
Prof. Dr. Manoj Kumar

20. 4. Generation: The development of the optical amplifier lead to
the 4. Generation of optical communication systems.
Schematic sketch of an erbium-doped fiber amplifier (EDFA).
Ref.: S.V. Kartalopoulos, Introduction to DWDM Technology
Introduction to Optical Communication – Lecture slide
Prof. Dr. Manoj Kumar

21. State of the Art optical communication system: Dense Wavelength Division Multiplex
(DWDM) in combination of optical amplifiers. The capacity of optical communication
systems doubles every 6 months. Bit rates of 10Tbit/s were realized by 2001.
Ref.: S. Kartalopoulos, WDWM Networks, Devices and Technology
Introduction to Optical Communication – Lecture slide
Prof. Dr. Manoj Kumar