Chapter 1 Introduction FOCS (10!12!12)

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Chapter 1

INTRODUCTION OF FIBER OPTICCOMMUNICATION SYSTEMS

Fiber-Optic Communications Systems, Third Edition.

Govind P. Agrawal


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Chapter Objectives

Understand and discuss Historical Perspective: Need for Fiber

Optic Communications, Evolution of Lightwave Systems.

Describe Basic Concepts: Analog and Digital Signals, Channel

Multiplexing, Modulation Formats.

Describe Optical Communication Systems

Describe Lightwave System Components: Optical Fibers, Optical

Transmitters, Optical Receivers

Apply the basic knowledge of Optiwave Simulation Software to

determine the quality parameters of Fiber Optic Communication

Systems


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Lecture 1

Introduction to

Fiber Optic Communication Systems(1)

Understand and discuss Historical Perspective: Need for Fiber

Optic Communications, Evolution of Lightwave Systems.

Describe Basic Concepts: Analog and Digital Signals,

Channel Multiplexing, Modulation Formats.


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What is the name of this communication system?


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The Modern Communication Systems:

Microwave Communication System (Including

Mobilphone System)

Satellite Communication System

Fiber Optic Communication System


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HISTORICAL PERSPECTIVE

Up to the end of the 18th century, human used mirrors, fire

beacons, smoke signals, signaling lamps, flags, and other

semaphore devices to convey a single piece of information,

The idea was extended further, following a suggestion of

Claude Chappe in 1792, to transmit mechanically codedmessages over long distances (~100 km) by the use of

intermediate relay stations.

The first such optical telegraph was put in service between

Paris and Lille (~ 200 km apart) in July 1794. By 1830, the

network had expanded throughout Europe.

The effective bit rate of such systems: B < 1 b/s


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INTRODUCTION



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Need for Fiber-Optic Communications

1830s - electrical communications -Morse code (B~10b/s).

Used of intermediate relay stations allowed communication

over long distances (~1000 km)

1866 - transatlantic telegraph cable

1876 - The invention of the telephone

1940 - coaxial-cable system, 3-MHz system, transmitting 300

voice channels

1948 - First microwave system, frequency of 4 GHz (B~100Mb/s)

1975 - Coaxial system (B~274 Mb/s) repeater spacing (~1 km)


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+ To carry telephone, internet, multimedia and various broadband data

applications.

+ 18,800 kilometres long; total capacity of 1.28 Tbit/s.

+ Dense wavelength Division Multiplexing DWDM


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USABLE SPECTRUM OF SILICA FIBER


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2000s

Water

spike

Attenuation versus Wavelength


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1970, fiber losses < 20 dB/km in the wavelength region near 1 m.

GaAs LD were demonstrated. The simultaneous availability of

compact optical sources and a low-loss optical fibers led to a

worldwide effort for developing FOCS.

The progress has indeed been rapid as evident from an increase in the

bit rate by a factor of100,000 over a period of less than 25 years.

Transmission distances have also increased from 10 to 10,000 km over

the same time period. As a result, the bit ratedistance product of modern lightwave systems

can exceed by a factor of107compared with the first-generation

lightwave systems.



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Evolution of Lightwave Systems



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Evolution of Lightwave Systems

The fourth generation used optical amplification for increasing

the repeater spacing and of wavelength-division multiplexing

(WDM) for enhancing the bit rate before and after 1992; bit rate

of 10Tb/s by 2001.

The fifth generation was concerned with extending the

wavelength range over which a DWDM system can operate

simultaneously (S/C/L band). The Raman amplification

technique can be used for signals in all three wavelength bands.



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BASIC CONCEPTS

Analog an Digital Signals


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Analog an Digital Signals

BASIC CONCEPTS


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Channel Multiplexing

BASIC CONCEPTS


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Modulation Formats

BASIC CONCEPTS


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BASIC CONCEPTS


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Modulation Formats

In the case of analog modulation: AM, FM and PMThe same modulation techniques: ASK, FSK and PSK

depending on whether the amplitude, frequency, or phase of

the carrier wave is shifted between the two levels of a binary

digital signal

The simplest technique consists of simply changing the signal

power between two levels, one of which is set to zero: onoff

keying (OOK) (ASK) to reflect the onoff nature of the

resulting optical signal. Most digital lightwave systems employ

OOK in combination with PCM.

BASIC CONCEPTS


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Lecture 2

Introduction toFiber Optic Communication Systems(2)

Describe Optical Communication Systems

Describe Lightwave System Components: Optical

Fibers, Optical Transmitters, Optical Receivers

Apply the basic knowledge of Optiwave Simulation

Software to determine the quality parameters of Fiber

Optic Communication Systems


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OPTICAL COMMUNICATION SYSTEMS

Optical communication systems use high carrier frequencies (

200THz). Microwave systems use smaller carrier frequency (20 GHz).

An increase in the information capacity of optical communication

systems by a factor of up to 10,000 is expected simply because of

such high carrier frequencies used for lightwave systems.


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Typical Fiber Optic communication systems


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Some of typical equipments in FOCS


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LIGHTWAVE SYSTEM COMPONENTS

Optical Fibers as a Communication Channel

o Most lightwave systems use optical fibers as the

communication channel because silica fibers can transmit

light with losses as small as 0.2 dB/km. Optical power

reduces to only 1% after 100 km


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Fundamental limits of silica fibers

C-band: supports early EDFA

C+L-band: support for EDFAs of today

Raman amplifiers can be used over all bands - new

(medium loss) bands are now applicable (as S & U

bands)

New fibers can reduce loss at E & S bands (however,

EDFA does not work here & Raman gain small)

O-band Original 1260-1360

E-band Extended 1360-1460

S-band Short 1460-1530

C-band Conventional 1530-1565

L-band Long 1565-1625

U-band Ultra-long 1625-1675

Band Description Wavelength (nm)

Inter- and Intra-modal dispersion

Attenuation (Loss)

Non-linear effects

Four-wave mixing (FWM)

Stimulated Raman & Brillouin

scattering (SRS,SBS)

Cross-phase & self-phase modulation (SPM,XPM

Polarization fluctuations

0.8 1.0 1.2 1.4 1.6 1.8

Wavelength (mm)

Water spike

Rayleigh scattering

Infrared absorption

Loss(dB/km)

100

50

10

1

0.5

0.1

5


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ADVANTAGES OF OPTICAL COMMUNICATIONS

1. Enormous Bandwidths. 2. Low transmission loss .

3. Immunity to cross talk

4. Electrical Isolation

5. Small size and weight 6. Signal security

7. Flexibility

8. Low cost and availability

9. ReliabilityThe lightwave technology, together with microelectronics, is

believed to be a major factor in the information age.


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5. Small size and weight



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5. Small size and weight


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Introduction on Optiwave Simulation Software


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Project Structure

OptiSystem Graphical User Interface


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OptiSystem Graphical User Interface

Placing Components in the Main Layout


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Placing Components in the Main Layout


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Lab 1 - Determining critical parameters of Fiber

Optic Communication system

Setting the working parameters for FOCS


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Setting the working parameters for FOCS


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Laser Spectrum

Spectrum at the Laser output and at the PhotoDiode input

Optical powers at the Modulator output


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Optical powers at the Modulator output

and at the Photodiode input

The quality parameters: BER Q of FOCS


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The quality parameters: BER, Q of FOCS

Chapter 1 Introduction FOCS (10!12!12)

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Transcript of Chapter 1 Introduction FOCS (10!12!12)