FUNDAMENTALS OF DWDM

TECHNOLOGY

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OBJECTIVESAFTER STUDYING YOU ARE ABLE TO……….

UNDERSTAND AND MASTER THE BASIC CONCEPTS, TRANSMISSION MODES AND STRUCTURE OF WDM.

UNDERSTAND WDM TRANSMISSION MEDIA.

UNDERSTAND KEY TECHNOLOGIES TO REALIZE WDM.

UNDERSTAND TECHNOLOGIES SPECIFICATIONS FOR WDM SYSTEMS.

CONTENTS

• DWDM OVERVIEW

• WDM TRANSMISSION MEDIA

• DWDM KEY TECHNOLOGIES

• TECHNOLOGIES SPECIFICATIONS FOR WDM SYSTEMS

DEVELOPMENT OF DWDM

1.GROWTH OF VOICE, DATA, NEW SERVICES

2.DESIRE FOR INFORMATION, COMMUNICATION.

1.DEVELOPED RAPIDLY…….

4 X 2.5GBPS 40 X 10GBPS 1.6TBPS

2.DEVELOPING TREND…….

OADM, OXC…

HOW TO INCREASE NETWORK CAPACITY

• DWDM IS QUICK, ECONOMICAL AND MATURE METHOD

• HIGH RATE TDM SIGNAL STM-1 STM-16 STM-64

• SDM – ADD FIBER , EQUIPMENT (TIME & COST)

WDM CONCEPT

ATM CELLS (λn)

IP PACKAGES (λ2)

SDH SIGNAL (λ1)

DIFFERENT SIGNALS WITH SPECIFIC WAVELENGTH ARE MULTIPLEXED INTO A FIBER FOR TRANSMISSION.

STRUCTURE OF DWDM SYSTEM

UNIDIRECTIONAL WDM TRANSMISSION

SINGLE FIBER UNIDIRECTIONAL TRANSMISSION

APPLICATION MODES-OPEN SYSTEM

OPEN WDM SYSTEM HAS NO SPECIAL REQUIREMENT FOR

MULTIPLEX TERMINAL OPTICAL INTERFACES, THE ONLY

REQUIREMENT IS THAT THESE INTERFACES MEET THE

OPTICAL INTERFACE STANDARD DEFINED IN ITU-T.

OSC

WDM SYSTEM COMPOSITIONS

TX1

TX2

TXn

RX1

RX2

RXn

OM/OA

OD/OA

OA

OFC OFC

F1

S1

F2

S2

Fn

Sn

Rm1

Rm2

Rmn

MPI-S MPI-RR’ S’

SD1

SD2

SDn

R1

R2

R3

• OPTICAL WAVELENGTH CONVERSION UNIT (OUT)

• OPTICAL MULTIPLEXER UNIT (OM)

• OPTICAL AMPLIFIER UNIT (OA)

• OPTICAL FIBER CHANNEL (OFC)

• OPTICAL DEMULTIPLEXER UNIT (OD)

• Transmitting transponder (Tx)

• Receiving Transponder (Rx)

ADVANTAGES OF DWDM

• TRANSPARENT MEDIA

• LONGHAUL TRANSMISSION

• HIGH CAPACITY

• USE EXISTING OPTICAL FIBER

• HIGH PERFORMANCE-TO-COST RATIO

• RELIABILITY

• EASY UPGRADING

BENEFITS OF DWDM INCREASES BANDWIDTH (SPEED AND DISTANCE)

DOES NOT REQUIRE REPLACEMENT OR UPGRADE

THEIR EXISTING LEGACY SYSTEMS

PROVIDES "NEXT GENERATION" TECHNOLOGIES TO

MEET GROWING DATA NEEDS

LESS COSTLY IN THE LONG RUN BECAUSE INCREASED

FIBER CAPACITY IS AUTOMATICALLY AVAILABLE;

DON'T HAVE TO UPGRADE ALL THE TIME

.

.

.Z MB/SZ MB/S

2.5 GB/S2.5 GB/S

10 GB/S10 GB/S

Y MB/SY MB/S

DWDMDWDM

• SIZE OF TRANSPORT PIPE DICTATED BY BIT RATE

• LIMITED CAPACITY GROWTH POTENTIAL

• GROWTH ACCOMPLISHED THROUGH

INFRASTRUCTURE UPGRADES

• SIZE OF TRANSPORT PIPE DICTATED BY BIT RATE

• LIMITED CAPACITY GROWTH POTENTIAL

• GROWTH ACCOMPLISHED THROUGH

INFRASTRUCTURE UPGRADES

• SIZE OF TRANSPORT PIPE INDEPENDENT OF BIT RATE

• VIRTUALLY UNLIMITED CAPACITY GROWTH POTENTIAL

• GROWTH ACCOMPLISHED WITHIN ESTABLISHED INFRASTRUCTURE

• OPTIMUM SOLUTION TO KEEP PACE WITH BUSINESS GROWTH

• SIZE OF TRANSPORT PIPE INDEPENDENT OF BIT RATE

• VIRTUALLY UNLIMITED CAPACITY GROWTH POTENTIAL

• GROWTH ACCOMPLISHED WITHIN ESTABLISHED INFRASTRUCTURE

• OPTIMUM SOLUTION TO KEEP PACE WITH BUSINESS GROWTH

TRADITIONAL CAPACITY EXPANSIONS

10 GB/S

OC-48/OC-48/STM-16STM-16

OC-12/OC-12/STM-4STM-4

600 MB/S 2.5 GB/S

OC-192/OC-192/STM-64STM-64

TIME DIVISION MULTIPLEXING

MORE FIBER

600 MB/S600 MB/S

CAPACITY ENRICHMENT WITH OPTICAL NETWORKING

BRIEF INTRODUCTION TO CWDM

• CWDM (COARSE WAVELENGTH DIVISION MULTIPLEXING)

DIFFERENCE BETWEEN CWDM AND DWDM:

• CARRIER CHANNEL SPACING OF CWDM IS WIDE.

• CWDM MODULATE LASER ADOPTS THE UNCOOLED LASER.

• THE CWDM CURRENTLY USED WORKS FROM 1271nm TO

1611nm,THE SPACING IS 20nm AND MULTIPLEX 18

WAVELENGTH CHANNELS.

• THE CWDM GREATLY REDUCES THE SYSTEM COST WHILE

PROVIDING CERTAIN AMOUNT OF WAVELENGTH AND

TRANSMISSION DISTANCE WITHIN 100Km.

CONTENTS

• DWDM OVERVIEW

• WDM TRANSMISSION MEDIA

• DWDM KEY TECHNOLOGIES

• TECHNOLOGIES SPECIFICATIONS FOR WDM SYSTEMS

STRUCTURE OF OPTICAL FIBER

CladdingCore

Coating

OPTICAL FIBER CONSISTS OF A CYLINDRICAL

GLASS CORE , A GLASS CLADDING AND A

PLASTIC WEAR-RESISTING COATING.

ATTENUATION OF OPTICAL FIBER

DISPERSION EFFECTS

• THE DEPENDANCE OF THE PHASE VELOCITY IN A MEDIUM ON THE OPTICAL FREQUENCY OR THE PROPAGATION MODE. IT CAN BE….

– CHROMATIC DISPERSION (CD)

– POLARIZATION MODE DISPERSION (PMD)

CHROMATIC DISPERSION

CD IS THE PHENOMENON OF DIFFERENT

WAVELENGTHS INSIDE AN OPTICAL SIGNAL

TRAVELLING AT DIFFERENT VELOCITIES ALONG A

FIBER AND ARRIVING AT RECIEVER DIFFERENT TIME

IN THE RECEIVER.

CD EFFECTS AND SOLUTIONS

EFFECTS • DECREASE OF PEAK POWER

• PULSE BROADENING

• BIT ERRORS

SOLUTIONS• USE OF DCM (DISPERSION COMPENSATION

MODULE)

• USE OF DCF (DISPERSION COMPENSATION FIBER)

WHICH

HAS NEGATIVE DISPERSION COEFFICIENT,IT CAN

COUNTERACT POSITIVE DISPERSION IN

TRANSMISSION.

CD COEFFICIENTS FOR VARIOUS FIBER TYPES

POLARIZATION MODE DISPERSION (PMD)

THE EFFECT OF DIFFERENT POLARIZATION MODES

(VERTICAL AND HORIZONTAL) OF A SIGNAL

STATISTICALLY TRAVELLING AT DIFFERENT VELOCITIES

DUE TO FIBER IMPERFACTIONS.

PMD EFFECTS AND SOLUTIONS

EFFECTS • DECREASE OF PEAK POWER

• PULSE BROADENING

• BIT ERRORS

SOLUTIONS• CAREFUL FIBER LAYING ( NO STRESS )

• USE OF NEW FIBERS WITH LOW PMD VALUES

• EXACT FIBER GEOMETRY

CONTENTS

• DWDM OVERVIEW

• WDM TRANSMISSION MEDIA

• DWDM KEY TECHNOLOGIES

• TECHNOLOGIES SPECIFICATIONS FOR WDM SYSTEMS

DWDM KEY TECHNOLOGIES

OPTICAL SOURCES

OPTICAL SUPERVISORY TECHNOLOGY

MULTIPLEXERSAND

DEMULTIPLEXERS

OPTICAL AMPLIFIERS

REQUIREMENTS OF OPTICAL SOURCES

• LARGE DISPERSION TOLERANCE

VALUE

• STANDARD AND STABLE

WAVELENGTH

LASER• 1. DIRECT MODULATION

• 2. ELECTRO-ABSORPTION (EA)

EXTERNAL

MODULATOR

• 3. MACH-ZEHNDER (M-Z) EXTERNAL

MODULATOR

DIRECT MODULATION

• OUTPUT LASER IS CONTROLLED BY INPUT

CURRENT.

• TRANSMISSION RATE < 2.5Gbps.

• TRANSMISSION DISTANCE < 100Km

LASERCURRENT

LD

ELECTRO-ABSORPTION (EA)

• SUPPORT LONG HAUL TRANSMISSION (2.5Gbps > 600Km)

• LESS CHIRP.

• HIGH DISPERSION TOLERANCE (2.5Gbps:7200 12800 ps/nm)

• HIGH RELIABILITY.

LD EA

VOLTAGE APPLIED

MECH-ZEHNDER EXTERNAL MODULATOR (M-Z)

• LONG DISPERSION LIMITED DISTANCE.

• HIGH COST.

• NEGLIGIBLE CHIRP.

• HIGH DISPERSION TOLERANCE.

LD

COMPARISON OF MODULATORS

TYPES DIRECT MODULATOR

EA MODULATOR

M-Z MODULATOR

MAX. DISPERSION TOLERATION (ps/nm)

1200~4000 7200~12800 >12800

COST MODERATE EXPENSIVE VERY EXPENSIVE

WAVELENGTH STABILITY

GOOD BETTER BEST

OPTICAL SUPERVISORY CHANNEL

• TRANSMIT RELATED MANAGEMENT,SUPERVISION

INFORMATION.

– OPERATING WAVELENGTH 1510nm.

– MONITORING RATE 2Mbps.

– ADD/EXTRACT.

• REQUIREMENT:NOT LIMIT PUMPING WAVELENGTH

OF OA,NOT LIMIT 1310nm SERVICE,AVAILABLE

WHEN OA FAILS,LONG DISTANCE TRANSMISSION.

ERBIUM DOPED FIBER AMPLIFIER (EDFA)

EDFA

ERBIUM DOPED FIBER AMPLIFIER (EDFA)

PUMPLIGHT

1550 nm SIGNAL LIGHT

DECAY

E3 EXCITED STATE

E2 META-STABLE STATE

1550 nm SIGNAL LIGHT

EDFA ENERGY LEVEL DIAGRAM

EDFA INTERNAL STRUCTURE

ADVANTAGES OF EDFA• WORKING WAVELENGTH IS CONSISTENT WITH

THE MINIMUM ATTENUATION WINDWOW OF

THE MON0MODE OPTICAL FIBER.

• HIGH COUPLING EFFICIENCY.

• HIGH ENERGY CONVERSION EFFICIENCY.

• HIGH GAIN,LOW NOISE FIGURE,LARGE OUTPUT

POWER AND MINIMUM CROSS-TALK.

• STABLE GAIN CHARACTERISTICS.

DISADVANTAGES OF EDFA

• GAIN WAVELENGTH RANGE IS

FIXED.

• GAIN BANDWIDTH UNFLATNESS.

• OPTICAL SURGE PROBLEM.

IMPACT OF GAIN FLATNESS IN LONG HAUL TRANSMISSION

CASCADING AMPLIFICATION OF AMPLIFIER GAIN UNFLATNESS

CASCADING AMPLIFICATION OF AMPLIFIER GAIN FLATNESS

STIMULATED RAMAN SCATTERING

STIMULATED RAMAN SCATTERING

(SRS) IS A PROCESS BY WHICH

ENERGY IS TRANSFERRED FROM

ONE WAVELENGTH TO A LONGER

WAVELENGTH THROUGH A

NONLINEAR SCATTERING PROCESS.

ADVANTAGES OF RFA

• GAIN WAVELENGTH IS DETERMINED BY

THE PUMPING LIGHT WAVELENGTH.

• SIMPLE STRUCTURE OF AMPLIFIER.

• NONLINEAR EFFECTS CAN BE REDUCED.

• LOW NOISE.

DISADVANTAGES OF RFA

• HIGH PUMP POWER,LOW EFFICIENCY AND

HIGH COST.

• INSTANTANEOUS GAIN,ADOPTING

BACKWARD PUMP FASHION.

• OPTICAL COMPONENTS AND OPTICAL FIBER

UNDERTAKE HIGH OPTICAL FIBER.

• CHARACTERISTICS OF GAIN ONLINE ARE NOT

CONSISTENT.

APPLICATION OF OA

ACCORDING TO ITS APPLICATION :

• BA – BOOSTER AMPLIFIER.

• LA – LINE AMPLIFIER.

• PA – PREAMPLIFIER .

MULTIPLEXER AND DEMULTIPLEXER

THIN-FILM FILTER

• THE THIN-FILM FILTER (TFF) IS A DEVICE USED

IN SOME OPTICAL NETWORKS TO MULTIPLEX

AND DEMULTIPLEX OPTICAL SIGNALS.

• USE MANY ULTRATHIN LAYERS OF DIELECTRIC

MATERIAL COATING DEPOSITED ON A GLASS

OR POLYMER SUBSTRATE.

• SUBSTRATE CAN BE MADE TO LET ONLY

PHOTONS OF A SPECIFIC WAVELENGTH PASS

THROUGH, WHILE ALL OTHERS ARE

REFLECTED.

THIN-FILM FILTER CONCEPT

ARRAYED WAVEGUIDE GRATING

AWG

MULTILAYER INTERFERENCE FILTERS

WAVEGUIDE GRATING DIFFRACTION

CONTENTS

• DWDM OVERVIEW

• WDM TRANSMISSION MEDIA

• DWDM KEY TECHNOLOGIES

• TECHNOLOGIES SPECIFICATIONS FOR WDM SYSTEMS

RELATED ITU-T RECOMMENDATION

• G.652 CHARACTERISTICS OF A SINGLE MODE OPTICAL FIBER CABLE.

• G.655 CHARACTERISTICS OF A DISPERSION SHIFTED SMF.

• G.661/G.662/G.663 RELEVANT RECOMMENDATION OF OA.

• G.671 CHARACTERISTICS OF PASSIVE OPTICAL COMPONENTS.

• G.957 OPTICAL INTERFACES RELATING TO SDH SYSTEMS.

• G.691 OPTICAL INTERFACES FOR SINGLE CHANNEL STM-64, STM-256,

SYSTEMS AND OTHER SDH SYSTEM WITH OA.

• G.692 OPTICAL INTERFACES FOR MULTI-CHANNEL SYSTEM WITH OA.

• G.709 INTERFACES FOR THE OPTICAL TRANSPORT NETWORK (OTN).

DISTRIBUTION OF OPTICAL WAVELENGTH AREA

• A FIBER HAS TWO LONG WAVELENGTH AND LOW LOSS

WINDOWS,1310nm WINDOW AND 1550nm WINDOW.BUT THE

COMMONLY USED WORKING WAVELENGTH RANGE FOR THE

ERBIUM-DOPED OPTICAL AMPLIFIER IS 192.10 TO 196.00 THz.

• NOMINAL CENTRAL FREQUENCY REFERS TO THE CENTRAL

WAVELENGTH CORRESPONDING TO EACH CHANNEL IN OPTICAL

WAVELENGTH DIVISION MULTIPLEXING SYSTEMS.CHANNEL

FREQUENCY ALLOWED IN G.692 IS BASED ON FREQUENCY AND

SPACING OF REFERENCE FREQUENCY 193.10 THz AND MINIMUM

SPACING 100GHz.