15-03-2011, 03:14 PM
presented by:
Alpina Kulkarni
DWDM_2.ppt (Size: 245.5 KB / Downloads: 378)
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