presented by:
Alpina Kulkarni

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Fiber Systems Dense Wavelength Division Multiplexing (DWDM)
Brief Overview
► Problems with increasing network demands
► Solutions proposed & their limitations
► Evolution of DWDM
► Technical details
► Drawbacks
► Ongoing Research
► Conclusion
► Growing Network Usage Patterns
► Issues
 Exponential increase in user demand for bandwidth
► Doubling of bandwidth requirement every 6-9 months
 Consistency in quality of services provided
 Keeping the cost of solutions at bay
► Solutions
 Increase channel capacity: TDM, WDM
 Statistical multiplexing of users: Multiple optical fibers
► Another glimpse at the solutions
► Limitations of current solutions
► Evolution of DWDM
What is DWDM?
Definition
 Dense wavelength division multiplexing (DWDM) is a fiber-optic transmission technique that employs light wavelengths to transmit data parallel-by-bit or serial-by-character
How does DWDM fair better?
► No O-E-O required
► Protocol & Bit Rate independence
► Increased overall capacity at much lower cost
 Current fiber plant investment can be optimized by a factor of at least 32
► Transparency
 Physical layer architecture à supports both TDM and data formats such as ATM, Gigabit Ethernet, etc.
► Scalability
 Utilize abundance of dark fibers in metropolitan areas and enterprise networks
► Capacity Expansion
Basic Components & Operation
► Transmitting Side
 Lasers with precise stable wavelengths
 Optical Multiplexers
► On the Link
 Optical fiber
 Optical amplifiers
► Receiving Side
 Photo detectors
 Optical Demultiplexers
Optical add/drop multiplexers
► Optical Amplifier
► Eliminates O-E-O conversions
► More effective than electronic repeaters
► Isolator prevents reflection
► Light at 980nm or 1480nm is injected via the pump laser
► Gains ~ 30dB; Output Power ~ 17dB
Drawbacks
► Dispersion
 Chromatic dispersion
 Polarization mode dispersion
 Attenuation
 Intrinsic: Scattering, Absorption, etc.
 Extrinsic: Manufacturing Stress, Environment, etc.
► Four wave mixing
 Non-linear nature of refractive index of optical fiber
 Limits channel capacity of the DWDM System
Ongoing Developments
► Nortel Networks
 Metro DWDM
 OPTera Long Haul 5000 Optical Line System
► Cisco Systems
 ONS 15200 Metro DWDM Solution
► Lucent Technologies
 LambdaXtreme Transport
 WaveStar OLS 1.6T
► Agility Communications & UC Santa Barbara
 Tunable Lasers used for multiple wavelengths
Conclusion
► Robust and simple design
► Works entirely in the Optical domain
► Multiplies the capacity of the network many fold
► Cheap Components
► Handles the present BW demand cost effectively
► Maximum utilization of untapped resources
► Best suited for long-haul networks