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FUNDAMENTALS OF DWDM
TECHNOLOGY
-
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.