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Dense Wavelength Division Multiplexing DWDM

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Title: 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.

4
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.

5
Historic Perspective and Background
  • Evolution of DWDM

6
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.

7
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.

8
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

9
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

10
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)

11
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

12
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.

18
Background
  • Principle of Total Internal Reflection

19
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

20
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

23
Background
  • Selectively Removing and Adding Wavelengths

24
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.

25
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.

26
Current Challenges / Constraints
  • Rayleigh Scattering

27
Current Challenges / Constraints
  • Absorption

28
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

29
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.

30
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.

31
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

32
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.

33
Current Challenges / Constraints
  • Four-Wave Mixing

34
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

35
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.

37
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.

38
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.

39
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.

40
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.

41
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.

42
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

43
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.
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