Dense wavelength division multiplexing

1. Fiber SystemsFiber Systems
Dense Wavelength DivisionDense Wavelength Division
MultiplexingMultiplexing (DWDM)(DWDM)
Tauseef khanTauseef khan

2. Brief OverviewBrief Overview
►Problems with increasing network demandsProblems with increasing network demands
►Solutions proposed & their limitationsSolutions proposed & their limitations
►Evolution of DWDMEvolution of DWDM
►Technical detailsTechnical details
►DrawbacksDrawbacks
►Ongoing ResearchOngoing Research
►ConclusionConclusion

3. Growing Network Usage PatternsGrowing Network Usage Patterns
► IssuesIssues
 Exponential increase in user demand for bandwidthExponential increase in user demand for bandwidth
► Doubling of bandwidth requirement every 6-9 monthsDoubling of bandwidth requirement every 6-9 months
 Consistency in quality of services providedConsistency in quality of services provided
 Keeping the cost of solutions at bayKeeping the cost of solutions at bay
► SolutionsSolutions
 Increase channel capacity: TDM, WDMIncrease channel capacity: TDM, WDM
 Statistical multiplexing of users: Multiple optical fibersStatistical multiplexing of users: Multiple optical fibers

4. Another glimpse at the solutionsAnother glimpse at the solutions
► WDM (Wavelength Division Multiplexing)WDM (Wavelength Division Multiplexing)
 Use of optical fibers to achieve higher speedsUse of optical fibers to achieve higher speeds
 Utilize wavelengths to multiplex usersUtilize wavelengths to multiplex users
 Allow continuous channel allocation per userAllow continuous channel allocation per user
 Increases the effective bandwidth of existing fiberIncreases the effective bandwidth of existing fiber
► TDM (Time Division Multiplexing)TDM (Time Division Multiplexing)
 Slotting of channelsSlotting of channels  simultaneous userssimultaneous users
 Increasing bit rate to maximize utilization of givenIncreasing bit rate to maximize utilization of given
bandwidthbandwidth

5. Limitations of current solutionsLimitations of current solutions
► WDMWDM
 Inefficient usage of full capacity of the optical fiberInefficient usage of full capacity of the optical fiber
 Capability of carrying signals efficiently over short distances onlyCapability of carrying signals efficiently over short distances only
► Improvements in optical fibers and narrowband lasersImprovements in optical fibers and narrowband lasers
 Birth of Dense WDM (DWDM)Birth of Dense WDM (DWDM)
► TDMTDM
 Dependency of Mux-Demux on bit rateDependency of Mux-Demux on bit rate
 Limitations on bit ratesLimitations on bit rates
► how fast can we go? (Decides how small the time slots can be)how fast can we go? (Decides how small the time slots can be)

6. Evolution of DWDMEvolution of DWDM
Late
1990’s
1996
DWDM
Early
1990’s
Narrowband WDM
1980’s
Wideband WDM
16+ channels16+ channels
100~200 GHz spacing100~200 GHz spacing
2~8 channels2~8 channels
200~400 GHz spacing200~400 GHz spacing
2 channels2 channels
1310nm, 1550nm1310nm, 1550nm
64+ channels64+ channels
25~50 GHz spacing25~50 GHz spacing

7. What is DWDM?What is DWDM?
► DefinitionDefinition
 Dense wavelength division multiplexing (DWDM) is a fiber-opticDense wavelength division multiplexing (DWDM) is a fiber-optic
transmission technique that employs light wavelengths totransmission technique that employs light wavelengths to
transmit data parallel-by-bit or serial-by-charactertransmit data parallel-by-bit or serial-by-character

8. How does DWDM fair better?How does DWDM fair better?
► No O-E-O requiredNo O-E-O required
► Protocol & Bit Rate independenceProtocol & Bit Rate independence
► Increased overall capacity at much lower costIncreased overall capacity at much lower cost
 Current fiber plant investment can be optimized by aCurrent fiber plant investment can be optimized by a
factor of at least 32factor of at least 32
► TransparencyTransparency
 Physical layer architecturePhysical layer architecture  supports both TDM andsupports both TDM and
data formats such as ATM, Gigabit Ethernet, etc.data formats such as ATM, Gigabit Ethernet, etc.
► ScalabilityScalability
 Utilize abundance of dark fibers in metropolitan areasUtilize abundance of dark fibers in metropolitan areas
and enterprise networksand enterprise networks

9. Capacity ExpansionCapacity Expansion

10. Basic Components & OperationBasic Components & Operation
► Transmitting SideTransmitting Side
 Lasers with precise stableLasers with precise stable
wavelengthswavelengths
 Optical MultiplexersOptical Multiplexers
► On the LinkOn the Link
 Optical fiberOptical fiber
 Optical amplifiersOptical amplifiers
► Receiving SideReceiving Side
 Photo detectorsPhoto detectors
 Optical DemultiplexersOptical Demultiplexers
► Optical add/dropOptical add/drop
multiplexersmultiplexers

11. Optical AmplifierOptical Amplifier
► Eliminates O-E-O conversionsEliminates O-E-O conversions
► More effective than electronic repeatersMore effective than electronic repeaters
► Isolator prevents reflectionIsolator prevents reflection
► Light at 980nm or 1480nm is injected via the pump laserLight at 980nm or 1480nm is injected via the pump laser
► Gains ~ 30dB; Output Power ~ 17dBGains ~ 30dB; Output Power ~ 17dB

12. DrawbacksDrawbacks
► DispersionDispersion
 Chromatic dispersionChromatic dispersion
 Polarization mode dispersionPolarization mode dispersion
► AttenuationAttenuation
 Intrinsic: Scattering, Absorption, etc.Intrinsic: Scattering, Absorption, etc.
 Extrinsic: Manufacturing Stress, Environment, etc.Extrinsic: Manufacturing Stress, Environment, etc.
► Four wave mixingFour wave mixing
 Non-linear nature of refractive index of optical fiberNon-linear nature of refractive index of optical fiber
 Limits channel capacity of the DWDM SystemLimits channel capacity of the DWDM System

13. Ongoing DevelopmentsOngoing Developments
► Nortel NetworksNortel Networks
 Metro DWDMMetro DWDM
 OPTera Long Haul 5000 Optical Line SystemOPTera Long Haul 5000 Optical Line System
► Cisco SystemsCisco Systems
 ONS 15200 Metro DWDM SolutionONS 15200 Metro DWDM Solution
► Lucent TechnologiesLucent Technologies
 LambdaXtreme TransportLambdaXtreme Transport
 WaveStar OLS 1.6TWaveStar OLS 1.6T
► Agility Communications & UC Santa BarbaraAgility Communications & UC Santa Barbara
 Tunable Lasers used for multiple wavelengthsTunable Lasers used for multiple wavelengths

14. ConclusionConclusion
► Robust and simple designRobust and simple design
► Works entirely in the Optical domainWorks entirely in the Optical domain
► Multiplies the capacity of the network many foldMultiplies the capacity of the network many fold
► Cheap ComponentsCheap Components
► Handles the present BW demand cost effectivelyHandles the present BW demand cost effectively
► Maximum utilization of untapped resourcesMaximum utilization of untapped resources
► Best suited for long-haul networksBest suited for long-haul networks

15. ReferencesReferences
[1] Introducing DWDM[1] Introducing DWDM
http://www.cisco.com/univercd/cc/td/doc/product/mels/dwdm/dwdm_fns.htmhttp://www.cisco.com/univercd/cc/td/doc/product/mels/dwdm/dwdm_fns.htm
[2] Fundamentals of DWDM Technology[2] Fundamentals of DWDM Technology
http://www.cisco.com/univercd/cc/td/doc/product/mels/dwdm/dwdm_ovr.htmhttp://www.cisco.com/univercd/cc/td/doc/product/mels/dwdm/dwdm_ovr.htm
[3] Dense Wavelength Division Multiplexing (DWDM)[3] Dense Wavelength Division Multiplexing (DWDM)
http://www.iec.org/online/tutorials/dwdmhttp://www.iec.org/online/tutorials/dwdm
[4] Dense Wavelength Division Multiplexing (DWDM) Testing[4] Dense Wavelength Division Multiplexing (DWDM) Testing
http://www.iec.org/online/tutorials/dwdm_testhttp://www.iec.org/online/tutorials/dwdm_test
[5] “Fiber-Optic Communications Technology” by D.K. Mynbaev, L.L. Scheiner, Pearson[5] “Fiber-Optic Communications Technology” by D.K. Mynbaev, L.L. Scheiner, Pearson
Education Asia, 2001 editionEducation Asia, 2001 edition
[6] “Dense wave nets' future is cloudy” by Chappell Brown, EETimes[6] “Dense wave nets' future is cloudy” by Chappell Brown, EETimes
http://www.eetimes.com/story/OEG20011221S0035http://www.eetimes.com/story/OEG20011221S0035
[7] Cisco Systems[7] Cisco Systems
http://www.cisco.com/en/US/products/hw/optical/ps1996/products_quick_reference_guidhttp://www.cisco.com/en/US/products/hw/optical/ps1996/products_quick_reference_guid
e09186a00800886bb.htmle09186a00800886bb.html
[8] Lucent Technologies[8] Lucent Technologies
http://www.lucent.com/products/subcategory/0,,CTID+2021-STID+10482-http://www.lucent.com/products/subcategory/0,,CTID+2021-STID+10482-
LOCL+1,00.htmlLOCL+1,00.html
[9] Nortel Networks: “OPTera Long Haul” & “Metro DWDM”[9] Nortel Networks: “OPTera Long Haul” & “Metro DWDM”
(http://www.nortelnetworks.com/products/01/optera/long_haul/dwdm/) &(http://www.nortelnetworks.com/products/01/optera/long_haul/dwdm/) &
(http://www.nortelnetworks.com/products/library/collateral/12001.25-03-02.pdf)(http://www.nortelnetworks.com/products/library/collateral/12001.25-03-02.pdf)
[10] Agility Communications[10] Agility Communications
http://agility.com/intervals/index.phtml?ID=93&f_code=1http://agility.com/intervals/index.phtml?ID=93&f_code=1