Dense Wavelength Division Multiplexing DWDM

1
Dense Wavelength Division Multiplexing (DWDM)

• The hunger for Bandwidth
• Frontiers Presentation
• Sam Njuki
• March 14 2001

2
Introduction

• Fiber optic cables.
• Time Division Multiplexing (TDM) technology
• - 2.4 Gb/s on a single fiber -
  increase the rate to 10 Gb/s.
• High bandwidth and the explosive growth of the
  internet
• Dense Wavelength Division Multiplexing
• - increase a single fiber capacity 16
  fold, to a throughput of 40 Gb/s.
• - meets the demand

3
Historic Perspective

• Evolution of Fiber Optic Transmission
• Circa 2500 B.C. Earliest known glass
• Roman Times Glass is drawn into fibers
• In the 1840s
• In 1954 Total internal reflection at a glass-air
  interface.
• In 1958 Invention of the laser by Bell-labs
• In 1960 Development of glass-clad fibers
• In 1961 Fibers with cores so small they carried
  light in only one waveguide mode.
• In 1970 Single-mode fibers with attenuation at
  the 633-nanometer helium-neon line below 20
  dB/km.

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Historic Perspective

• In 1961 Fibers with cores so small they carried
  light in only one Since the early 1980s massive
  computerization and deployment of fiber optic
  cables.
• Time Division Multiplexing (TDM)
• Industry's acceptance of SONET and SDH
• TDM equipment installed today utilizes less than
  1 of the intrinsic capacity of the fiber where
  STM-64/OC192 is being deployed.
• Early WDM began in the late 1980s - 2
  widely spaced wavelengths in the 1310 nm and 1550
  nm
• The early 1990s saw a second generation of WDM
  - 2 to 8 channels were used spaced at an
  interval of about 400 GHz in the
  1550-nm window.
• By the mid-1990s, dense WDM (DWDM) systems
  - 16 to 40 channels and spacing from 100 to
  200 GHz.

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Historic Perspective and Background

• Evolution of DWDM

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Background

• The Growing Demand
• Communication, - narrowband voice signals
  - high quality visual, audio, and data context.
• Every aspect of human interplay - from
  business, to entertainment, to government, to
  academia
• Internet
• Telecommunications industry, however, is
  struggling to keep pace with these changes.

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Background

• Bandwidth demand is driven by
• Growing Competition
• Government deregulation and market-driven
  economic stimulation.
• US long-distance market (1984) - revenues and
  access lines have grown 40 - investment in
  outside plant has increased 60.
• Telecommunication Reform Act (1996 )
• Strategy of price reduction
• maximizing the available capacity of network
  infrastructures and providing enhanced
  reliability.

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Historic Perspective and Background

• Network Survivability
• Carriers' need to guarantee fail-safe networks.
• Carriers have broadened route diversity through
  ring configurations or point-to-point networks
• To achieve 100 reliability, however, requires
  that spare capacity be set aside and dedicated
  only to a backup function.
• New Applications
• Video, high resolution graphics, and large volume
  data processing
• Frame Relay and ATM
• Internet usage, which some analysts predict will
  grow by 700annually in coming years.
• Cellular and PCS

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Background

• Achieving Bandwidth Capacity GoalsCarriers
  have three possible solutions
• Install new fiber - Deploying new fiber and
  transmission equipment. -The average cost
  estimated to be about 70,000 per mile. -
  The right-of-way. - Single-mode fiber.
• Higher Speed TDM- Deploying STM-64/OC-192 (10
  Gb/s) - single-mode fiber
• - Dispersion has a 16 times greater effect
  with STM-64/OC-192 equipment than with
  STM-16/OC-48.
• - NZDSF - costs some 50 more than SMF.
• - Carrier transmission power

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Background

• Deploy DWDM - multiplies the simple 2.4
  Gb/s system by up to 16 times.
• - 16 channel system supports 40 Gb/s
• - 40 channel system under development
  will support 100 Gb/s, the equivalent of
  ten STM-64/OC-192 transmitters.
• Practical Considerations of DWDM Deployment
• Based on bit rate alone, DWDM has a fourfold
  advantage even over the latest--albeit
  nascent--TDM option, STM-64/OC-192.
• Compatibility with Fiber Plant - majority of
  the legacy fiber plant cannot support high bit
  rate TDM - Non-zero dispersion shifted
  fiber (NZDSF)

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Background

• Transparency and Interoperability -
  interoperability between all vendors'
  transmission equipment
• - Vendor independent and conform to
  international standards - ITU
  channel spacing and OSI model - support
  mixed protocols and signal formats.
• Migration and Provisioning Strategy - Ability
  to expand - Channel upgrade capability -
  long-term solution and short-term fix
• Network Management - international standards
  - interface with the carrier's existing
  operating system - provide direct connection
  - migration to optical networks.
• Technical Constraints

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Background

• Dense Wavelength Division Multiplexing

13
Background
14
Background

• Enabling Technologies
• Optical filters and narrowband lasers
• flat-gain optical amplifier
• Improved optical fiber - EDFAs
• Fiber Bragg gratings used in optical add/drop
  multiplexers.

15
Background

• Anatomy of a DWDM system

16
Background

• Components and Operation
• Light Sources - LEDs and Lasers Figure shows
  the general principles of launching laser light
  into fiber.
• Typical Laser Design

17
Background

• Light Detectors - photodetectors
• Optical Fibers
• How Fiber Works - guide lightwaves
  with a minimum of attenuation
• Core and cladding - fine threads of glass in
  layers
• Total internal reflection - Beams pass
  from a more dense to a less dense material.
  - The incident angle is less than the critical
  angle.

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Background

• Principle of Total Internal Reflection

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Background

• Single-mode fiber - has a small core that
  allows only one mode of light at a time
  through the core.
• single-mode fibers are preferred for longer
  distance and higher bandwidth applications,
  including DWDM. - fidelity of the signal
  is better retained over longer distances -
  modal dispersion is greatly reduced. -
  large information-carrying capacity - low
  intrinsic loss
• Optical Amplifiers
• Limits to how long a fiber segment can propagate
  a signal
• Before optical amplifiers - Repeaters

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Background
21
Background

• Erbium-Doped Fiber Amplifier Design

22
Background

• signals can travel for up to 120 km (74 mi)
  between amplifiers.
• regenerated between 600 to 1000 km (372 to 620
  mi)
• Multiplexer
• Demultiplexer
• Optical Add/Drop Multiplexers - can remove/
  add wavelength while passing others on.
• Optical networks - OADMs.
• OADMs are similar to SONET ADM - no conversion of
  the signal from optical to electrical takes place
  

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Background

• Selectively Removing and Adding Wavelengths

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Background

• Interfaces to DWDM
• support standard SONET/SDH -
  OC-48c/STM-16c interface operating at the 1310-nm
• metropolitan area and access networks are
  commonly supported Ethernet (including Fast
  Ethernet and Gigabit Ethernet), ESCON, Sysplex
  Timer and Sysplex Coupling Facility Links, and
  Fibre Channel.
• The new 10 Gigabit Ethernet standard is supported
  using a very short reach (VSR) OC-192 interface
  over MM fiber between 10 Gigabit Ethernet and
  DWDM equipment.
• Transponders - convert the signal to electrical
  and drive a standard interface to the client.

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Current Challenges / Constraints

• Transmission Challenges
• Attenuation
• Attenuation is caused by - intrinsic
  factors primarily scattering and absorption
  - extrinsic factors, including stress from the
  manufacturing process, the environment,
  and physical bending.
• Rayleigh scattering - is an issue at shorter
  wavelengths
• Attenuation due to absorption - is an issue at
  longer wavelengths - the intrinsic
  properties of the material - impurities
  in the glass, and any atomic defects in the
  glass.
• These impurities absorb the optical energy,
  causing the light to become dimmer.

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Current Challenges / Constraints

• Rayleigh Scattering

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Current Challenges / Constraints

• Absorption

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Current Challenges / Constraints

• Dispersion
• Dispersion is the spreading of light pulses as
  they travel down optical fiber. Dispersion
  results in distortion of the signal, which limits
  the bandwidth of the fiber.
• Principle of Dispersion

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Current Challenges / Constraints

• Two general types of dispersionChromatic
  Dispersion - is linear
• Chromatic dispersion occurs because different
  wavelengths propagate at different speeds.
• Increases as the square of the bit rate.
• Polarization Mode Dispersion - is nonlinear.
• Polarization mode dispersion (PMD) is caused by
  ovality of the fiber shape as a result of the
  manufacturing process or from external stressors.
  
• Smearing of the signal
• Changes over time PMD is generally not a problem
  at speeds below OC-192.

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Current Challenges / Constraints

• Fiber Non Linearities
• Because nonlinear effects tend to manifest
  themselves when optical power is very high, they
  become important in DWDM.
• These nonlinearities fall into two broad
  groups
• - scattering phenomena
• - refractive index phenomena.
• Scattering Phenomena - Stimulated Brillouin
  Scattering (SBS) fill in - Stimulated
  Raman Scattering (SRS) - SRS is a
  wideband phenomena that affects the entire
  optical spectrum that is being
  transmitted. - its impact worsens as
  power is increased and as the total
  width of the DWDM spectrum widens.

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Current Challenges / Constraints

• Solution
• use moderate channel powers and densely packed
  channel plan that minimizes the overall width of
  the spectrum.
• Refractive Index Phenomena
• This group of nonlinearities includes -
  self-phase modulation (SPM) - cross-phase
  modulation (CPM) - four-wave mixing (FWM).
• SPM - This phenomena causes the signal's
  spectrum to widen and can lead to crosstalk
  or an unexpected dispersion penalty.
• CPM

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Current Challenges / Constraints

• Four-wave mixing - results in
  cross-talk and signal-to-noise degradation.
  - troublesome in the dispersion shifted fiber
  that is used to propagate
  STM-64/OC-192. - limit the channel
  capacity of a DWDM system.
• Solution
• This prompted the invention of NZ-DSF, which
  takes advantage of the fact that a small amount
  of chromatic dispersion can be used to mitigate
  four-wave mixing.
• As a result, carriers that opt for STM-64/OC-192
  equipment to relieve today's congestion may
  unintentionally be limiting their ability to
  grow capacity through future deployment of DWDM.

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Current Challenges / Constraints

• Four-Wave Mixing

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Principals and societal effects

• Ciena Corporation
• MultiWave CoreDirector - 640 Gb/s of full duplex
  switching in a single bay. It supports 256
  OC-48/STM-16 or 64 OC-192/STM-64 interfaces, with
  the ability to support OC-768/STM-256 in the
  future.
• MultiWave CoreStream is an advanced DWDM optical
  transport system with capacity of 2
  Terabits/second over a single fiber.
• Lucent Technologies
• AllWave(TM) Fiber Lucent Technologies was one of
  the first to demonstrate transmission of a
  trillion bits of data per second (more than all
  the world's Internet traffic) on a single strand
  of TrueWave fiber
• Fujutsi Network Communication, Alcatel, Cisco,
  Ericsson, Corvis, Harmonic, ADVA Optical
  Networking, Alidian Networks, etc

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Principals and societal effects

• Applications for DWDM
• DWDM is ready made for long-distance
  telecommunications operators that use either
  point-to-point or ring topologies.
• Development of self-healing rings
• Building or expanding networks
• Network wholesalers can lease capacity, rather
  than entire fibers,
• The transparency of DWDM systems to various bit
  rates and protocols.
• Utilize the existing thin fiber
• DWDM improves signal transmission

36
Market and Opportunities

• KMI Corporation
• Newport, RI, USA (12/12/00) The DWDM systems
  market will grow with a CAGR of 43 through 2005
  when the market will reach 54 billion,
• The DWDM systems market jumped from 4.2 billion
  in 1999 to 8.9 billion in 2000.
• From 1.7 billion in 1997, the market has grown
  at a 73 CAGR over the last four years.
• This growth reflects several trends - a
  maturation of the long distance segment of
  the DWDM equipment market - stiffening
  competition that will lead to price
  pressures - shorter-distance products in the
  market.

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Market and Opportunities

• By 2005, the short distance segment will exceed
  9.6 billion and represent 18 of the market.
• From 1999 to 2000 - the number of vendors
  offering DWDM system-level products grew
  from 15 to 30 - the number of carriers that
  have deployed DWDM climbed from 75 to
  175. - the number of contracts for DWDM will
  double from 75 to 150.
• Such growth reflects the tremendous demand
  long-distance carriers face for transporting
  bandwidth.
• Lucent Technologies - five-year agreement with
  Bell Atlantic valued at approximately 500
  million for optical networking, including DWDM,
  network management software and SONET
  transmission equipment.

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Market and Opportunities

• According to Dell'Oro Group, Lucent captured the
  largest market share - 34 percent (or
  approximately 1.3 billion) - of the 3.8 billion
  global DWDM equipment market in 1999.
• Lucent will install the DWDM optical networking
  system in the new, 900- mile (1,300 km) route
  between Xian and Wuhan which is worth more than
  10 million.
• "Getting an early lead in this market will prove
  to be very important," said Scott Clavenna,
  principal analyst at Pioneer Consulting, which
  has forecast the metro DWDM market to grow to
  nearly 1 billion by 2003.
• Cahners In-Stat Group projects as the Internet
  Service Provider (ISP)-driven, e-commerce economy
  continues to expand, DWDM market revenue will hit
  21.5 billion in 2004. In 1999, the DWDM systems
  market revenue was 4 billion, all of which was
  attributed to long haul applications.

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Market and Opportunities

• The Future of DWDM
• Building Block of the Photonic Network
• Deployment of DWDM is a critical first step
  toward the establishment of photonic networks in
  the access, interoffice, and interexchange
  segments of today's telecommunication
  infrastructure.

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Market and Opportunities

• Photonic network.
• DWDM systems with open interfaces -
  flexibility to provide SONET/SDH,
  asynchronous/PDH, ATM, Frame Relay, and
  other protocols over the same fiber. -
  eliminate the need for additional
  high-performance optical transmitters
• Freedom to provision services and reduce
  long-term costs.
• Deployment of DWDM will allow - new
  services to come on-line more quickly -
  contain costs so that customers afford new
  services - overcome technological barriers
  associated with more traditional
  solutions.

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Market and Opportunities

• Adel Saleh, head of the broadband access research
  department at ATT Labs in Red Bank, N.J.,
  projects that cost per network node will drop by
  a factor of 10 every five years, starting at 1
  million in 1995. Through the next year or two, he
  says, WDM will be economical only for backbone
  networks. Once cost drops to 100,000 a node, the
  technology will make sense for metropolitan and
  regional networks, starting with service to large
  businesses. Saleh expects that residential access
  in large apartment buildings will follow after
  costs drop to 10,000 a node in about 2005, with
  WDM reaching individual homes once costs decline
  to about 1,000 in 2010.
• cable companies - video-on-demand, high-speed
  Internet access.
• Solution for New World business strategy.Cahners
  points - the days when a business, will require a
  phone network for voice applications alone are
  fleeting.

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Research Presentation Summary

• What the future holds
• Two-way video communication
• Digital video for our everyday use at home and at
  work.
• Change from voice telephony to digital data heavy
  with video to require multiplying backbone
  transmission capacity.
• With DWDM systems, a television station is going
  to be able reserve one wavelength from its studio
  to its transmitter and another to the local cable
  companyand transmit both signals in digital
  video formats not used on the phone network.
• The Ultimate Squeeze - reducing the
  space between wavelengths - expanding
  the range of transmission wavelengths
  -better EDFAs

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Research Presentation Summary

• Develop better equipment for switching and
  manipulating the various wavelengths after the
  signal emerges from the optical pipe.
• WDM is creating huge new information pipelines
  that will bring better service at lower cost. But
  the real information revolution wont come until
  cheap WDM pipelines reach individual residences.
• MetroRED Telecom Group Ltd in Brazildeploys
  CIENA's MultiWave CoreStream
• Sprint Telecommunications deploys CIENAs
  MultiWave 1600
• DWDM will be especially attractive to companies
  that have low fiber count cables that were
  installed primarily for internal operations but
  that could now be used to generate
  telecommunications revenue.