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8/19/2019 PC481 Course Note1ád

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PC481 Fiber OpticsPC481 Fiber Optics

Fall 2010Fall 2010Instructor: Dapeng ZhouInstructor: Dapeng Zhou


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Lecture 1Lecture 1

Introduction to PC481

Chapter 1:

Overview of Optical Fiber Communications


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Introduction to PC481Introduction to PC481 Course Description:

Types of optical fibers. Basic theory: characteristics, numerical aperture,losses, dispersion, modes. Passive fiber devices: couplers, connectors,

splices. Light sources: LED, solid and semiconductor lasers. Modulators.Detectors. Systems design. The major emphasis is on fundamentals andon individual devices which make up the system rather than on detaileddesign of optical communication networks.

Contents:1. Overview of optical fiber communications (Chapter 1)

2. Optical fibers: structures, waveguiding, fabrication and optical cable(Chapter 2)

3. Signal degradation in optical fibers (Chapter 3)

4. Optical sourses: Laser diodes and LEDs (Chapter 4)

5. Power launching and coupling (Chapter 5)

6. Photodetectors (Chapter 6)

7. Photonic transmission systems (Chapter 7)

8. Wavelength-division multiplexing (Chapter 8)


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InstructorsInstructors Lecture instructor: Dapeng Zhou, Science Building, Room N2079

(519)884-0710, ext. 2974

[email protected]

Office hour: Fridays 13:00 pm-15:00 pm

Lab instructor: Hasan Shodiev, Science Building, Room N2086

(519)884-0710, ext. 2461 [email protected]


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Text BookText Book

Optical fiber communications, by Gerd Keiser, 4th edition,McGraw Hill, 2011. (The 3rd edition is no long in print; it isOK if you already have it.)


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EvaluationEvaluation

Assignment: 20% Lab: 25% (At least 12.5% to pass)

Midterm: 20% (End of October 2010) Final exam: 35%


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Chapter 1Chapter 1Overview of Optical Fiber CommunicationsOverview of Optical Fiber Communications


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OpticsOptics Optics is an old subject involving the generation,

propagation & detection of light.

Optical theory development:

Ray optics: short wavelength

↓

Wave optics: scalar approximation

↓

Electromagnetic optics: complete classical treatment

↓

Quantum optics: explanation of all optical phenomena

Quantum Optics

Electromagnetic Optics

Wave

Optics

Ray Optics

Chapter 1 Overview of Optical Fiber CommunicationsChapter 1 Overview of Optical Fiber Communications


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PhotonicsPhotonics Optoelectronics: refers to devices & systems that are

essentially electronics but involve lights, such as LED, liquid

crystal displays & array photodetectors.

Quantum Electronics: is used in connection with devices &

systems that rely on the interaction of light with matter, suchas lasers & nonlinear optical devices.

Quantum Optics: Studies quantum & coherence properties of

light.

Lightwave Technology: describes systems & devices that are

used in optical communication & signal processing.

Photonics: in analogy with electronics, involves the control of

photons in free space and matter.



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The Scope of Photonics:The Scope of Photonics:

1- Generation of Light (coherent & incoherent)

2- Transmission of Light (through free space, fibers,

imaging systems, waveguides, …)

3- Processing of Light Signals (modulation, switching,amplification, frequency conversion, …)

4- Detection of Light (coherent & incoherent)



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At sending end: Data are transferred over the communication channel bysuperimposing the information onto an EM wave ( known as Carrier)

At the destination, the information is removed from the carrier wave

and processed as desired


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Basic components of optical fiber linkBasic components of optical fiber link

Optical fibersStep/Graded-index; single-mode/multimode

Sources for optical transmitters

Semiconductor/fiber lasers; LEDs Detectors for optical receivers

Pin photodetector/Avalanche photdiodes

Signal processing equipmentsModulators; multiplexer/demultiplexer; couplers

Optical amplifiers

Erbium-doped fiber amplifier (EDFA)


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Elements of an optical fiber transmission link


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MilestonesMilestones

Three major developments are responsible forrejuvenation of optics & its application in

modern technology:

1- Invention of Laser

2- Fabrication of low-loss optical Fiber

3- Development of Semiconductor

Optical Device



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Evolution of fiber Evolution of fiber --optic systemsoptic systems

1950s:Imaging applications inmedicine & non-destructive testing,

lighting

1960s:Research on lowering the fiber

loss for telecom. applications.

1970s:Development of low loss fibers,

semiconductor light sources &

photodetectors

1980s:single mode fibers (OC-3 to

OC-48) over repeater spacings of 40km.

1990s:Optical amplifiers (e.g. EDFA),

WDM (wavelength division

multiplexing) toward dense-WDM.


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UnitUnit

Decibels (dB) – ratios or relative unitsIn designing and implementing an optical fiber link, it is

convenient to reference the signal level either to some absolute

value or to a noise level.

Power ratio in dB =

and are optical powers in mW

2

1

10log P

P

1P 2P



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UnitUnit


The dBm – absolute valueDecibel power level referred to 1 mW

Power level = 110log 1P

mW


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ExamplesExamples


3dB loss

200 µW in dBm unit

2

1

3 10 log( )PdBP

− =

3/102

1

10 0.5P

P

−

= ≈

6

3

( ) 200 1010log[ ] 10log[ ] 7.0

1 1 10

P W W P dBm

mW W

−

−

×

= = = −

×


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Basic fiber optic system modelBasic fiber optic system model


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System performanceSystem performanceBit Error Rate (BER)

Probability of error per bit

Receiver Sensitivity

Minimum number of photons per bit necessaryto guarantee that the BER is smaller than a

prescribed rate

Design Strategy

Attenuation/dispersion-limited performance


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WDM: wavelength-division multiplexing

WDM technology: The technology of combining a number of

wavelegnth onto the same fiber is known as WDM


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TX1

TX2

TXn

MUX

RX1

RX2

RXn

De

MUXOA

OAOA

SMF

components for today’s typical

optical fiber communication

TX: optical transmitter e.g. laser, modulator etc…

RX: optical receiver e.g. photodiode etc…

OA: optical ampli fier e.g. EDFA, SOA etc…

SMF: single mode fiber

MUX: optical wavelength multiplexer

DeMUX: optical wavelength demultiplexer

Conceptual WDM systems


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Optical NetworksOptical Networks

Point-to-point links VS Complex networks

Basic Topologies: Logical manner in whichnodes are linked together

Standards (SONET/SDH) : Specify formats for

optical signals so they can be shared between

networks



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Early application of fiber optic communicationEarly application of fiber optic communication

Digital link consisting of time-division-multiplexing (TDM) of 64 kbps voice

channels (early 1980).

The fundamental building block is a 1.544 Mb/s transmission rate known as a T1

rate. At any level, a signal at the designated input rate is multiplexed with other

input signals at the same rate.

Digital transmission hierarchy used in the North American telephone network


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SONET & SDH StandardsSONET & SDH Standards

SONET (Synchronous Optical NETwork) is the network standard used in northAmerica & SDH (Synchronous Digital Hierarchy) is used in other parts of the

world. These define a synchronous frame structure for sending multiplexed digital

traffic over fiber optic trunk lines.

The basic building block of SONET is called STS-1 (Synchronous Transport Signal)with 51.84 Mbps data rate. Higher-rate SONET signals are obtained by byte-

interleaving N STS-1 frames, which are scramble & converted to an Optical Carrier

Level N (OC-N) signal.

The basic building block of SDH is called STM-1 (Synchronous Transport Module)

with 155.52 Mbps data rate. Higher-rate SDH signals are achieved by

synchronously multiplexing N different STM-1 to form STM-N signal.


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STM-649953.28STS-192OC-192

STM-324976.64STS-96OC-96

STM-162488.32STS-48OC-48

STM-81244.16STS-24OC-24

STM-4622.08STS-12OC-12

STM-1155.52STS-3OC-3

-51.84STS-1OC-1

SDH equivalentLine rate (Mb/s)Electrical levelSONET level

SONET & SDH transmission ratesSONET & SDH transmission rates


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SONET multiplex hierarchySONET multiplex hierarchy

STS: Synchronous transport signal

SPE: Synchronous payload envelope

VT: Virtual tributary



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DWDM employmentDWDM employment



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