OPTICAL

COMMUNICATIONS Lecture notes for LE426

by

Urachada Ketprom

June 2012 – October 2012

1

Today’s Agenda

• Who is who?

• Instructor: Urachada Ketprom in a nutshell

• Who are you?

• Syllabus

• Course Schedule

• Course Homework and Project

• Add/Drop/Withdraw

• Overview of optical communications

• Optical transmission

• Optical components

• Optical communication

• Optical network

2

Who am I in a nutshell?

3

Educational background

4

Education

Ph.D., Electrical Engineering, University of Washington, Seattle, WA, September

2005

Dissertation: Line-of-sight propagation of optical wave through multiple-scatter

channel in

optical wireless communication system

MSEE, Electrical Engineering, University of Washington, Seattle, WA, June 1999

BSEE, Electrical Engineering, Northwestern University, Evanston, IL, June 1997

Research Interest

RFID applications, Traceability system, Electromagnetics theory and devices

Channel characterization for free space optics (FSO) communication, Optical

communication, Optical wireless communication,

Current Workplace www.etda.or.th

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6

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Optical Wireless Communication(OWC)

• Free space optics (FSO)

• Line-of-sight propagation

• “Fiberless” optics transmission

• Solution of “Last mile” problem

• Advantages • Low cost

• Easy installation

• High security

• Freedom from FCC

www. freespaceoptics.org

Disadvantage – Poor performance in

adverse weather

– Fog, rain, snow, low clouds

Effect of fog is dominant: its size is the most comparable to optical wavelength

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7

OWC Links in Fog

Bloom et.al

[2003]

Design engineer

Truly understanding the effect of fog

“Channel modeling”

Who are you?

5 Ws questions

• WHO?

• WHAT?

• WHEN?

• WHERE?

• WHY?

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Syllabus time!!! • LE 426 OPTICAL COMMUNICATIONS

• • Instructor: Urachada Ketprom • • Prerequisite: LE 200 •

• Textbook: Harry J. R. Dutton, Understanding Optical Communications, International

• Technical Support Organization, http://www.redbooks.ibm.com.

• • Objective: The course objective is to provide a basic understanding of present optical

communication systems as well as future engineering challenges

• • Course Description: • This course contains an introduction to the fundamental principles and components of optical

communications. The course objective is to provide a basic understanding of present optical communication systems as well as future engineering challenges. The course covers the basic concepts of light transmission in optical fiber channels, channel multiplexing, wavelength division multiplexing, and fiber optics. The course also includes the basic function principles of optical components such as optical fiber, light emitting diodes, lasers, optical amplifiers, optical filters, and optical receivers

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LE 426 Optical Communications

Lecture Time: Tuesday 1:30 pm - 4:30 pm

Evaluation: Midterm (25 points)

Final Exam (35 points)

Attendant and Assignment (20 points)

Project (20 points)

Lecture Schedule:

Start: June 26th,2012

End: October 4th,2012

10

15 weeks of lectures

• Week 1: Chapter 1 Introduction

• Week 2: Chapter 2 Optical Fiber (part I) • Week 3: Chapter 2 Optical Fiber (part II)

• Week 4: Chapter 3 Optical Sources • Week 5: Chapter 4 and 5 Optical Detectors and Optical Devices

• Week 6: Midterm Examination • Week 7: Chapter 5 Optical Devices

• Week 8: Chapter 6 Fiber Manufacture, Cables and Connectors

• Week 9: Chapter 7 Optical Communication Systems (part I)

• Week 10: Chapter 7 Optical Communication Systems (part II)

• Week 11: Chapter 8 Optical Link Connections in Electronic Networks

• Week 12: Chapter 9 Wavelength Division Multiplexing

• Week 13: Chapter 10 Lightwave Networks

• Week 14: Chapter 11 Fiber in the (Local) Loop-FITL • Week 15: Chapter 12 Research Directions

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Chapter 1 Introduction

THEN

• Man and fire signal

(beacon)

source: http://en.wikipedia.org/wiki/Beacon

NOW

High Speed Communication

source: http://2.bp.blogspot.com

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Milestones of optical communications

The invention of the LASER (in the late 1950's)

LASER = Light Amplification by Stimulated Emission Radiation

The development of low loss optical fiber (1970's)

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.

The invention of the optical fiber amplifier (1980's)

Erbium Doped Fiber Amplifier (EDFA) works in 1550 nm band

The invention of the in-fiber Bragg grating (1990's)

Fiber Bragg gratings are used to stabilize the output of a laser

and to filter out wavelengths in a WDM system.

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Why Optical Communications?

Bandwidth, bandwidth, bandwidth...

One fiber can carry up to 6.4 Tb/s (1012b/s) or 100 million conversations simultaneously

Optical frequencies are much higher than electronic frequencies

Much higher modulation frequencies ⇒ greater transmission rates

In optical links, bandwidth is much less dependent on link length than in baseband electronic links

Optical attenuation is independent of modulation frequency

An optical communication system can be upgraded to higher bandwidth by replacing the transmitters and receivers, but not the cable (using Wave Division Multiplexing = WDM)

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Advantages outweighs disadvantages

Main Advantages

• Weight and size

• Material cost

• Information capacity

• No electrical connection

• No electromagnetic

interference

• Distances between

regenerators

• Open ended capacity

• Better security

Main Disadvantages

• Installation cost

• Joining cables: Pigtailing

• Bending cables: Light

Escaping

• Slow standards development

• Gamma radiation

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Wavelength, not frequency

• Light can be characterized in terms of its wavelength

• Analogous to the frequency of a radio signal

• The wavelength of light is expressed in microns or

nanometers

• The visible light spectrum ranges from ultraviolet to infrared

• Optical fiber systems operate in three IR windows around

800 nm,1310 nm and 1550 nm

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Optical Transmission

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Optical components

• Source: Laser

• Channel: Fiber optics

• Receiver: Detectors

• Others

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Optical communication system

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Media in the fiber

optical channel

1.Voice(SONET/Te

lephony) -The

largest traffic

2. Video(TV)

over Hybrid Fiber

Coaxial (HFC) or

Fiber-Twisted

Pair/Digital

Subscriber Loops

(DSL)

3. Data–Internet

traffic

Optical Network

• Networks may be characterized by their geographic

extent such as:

• . Local Area Network (LAN)

• . Metropolitan Area Network (MAN)

• . Wide Area Network (WAN)

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Optical communication conclusion

• Coaxial cable is made of copper, fiber optics is made of

glass

• Most popular wavelengths for fiber optic waveguide:

0.8 microns, 1.3 microns, 1.55 microns

- Optical communication has advantages over radio wave

communication in weight and size but has disadvantages

in installation cost.

- Optical wireless communication is best operating when

the weather is clear.

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Next class

• Please review your old physics book

• Snell’s law? Reflection , Refraction, Diffraction

• Chapter 2 : Optical Fibers

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