of 65 /65
1 © 2001, Cisco Systems, Inc. All rights reserved. © 2001, Cisco Systems, Inc. All rights reserved. © 2001, Cisco Systems, Inc. All rights reserved. Cisco Optical Workshop DWDM January 31, 2004

Cisco DWDM

Embed Size (px)

DESCRIPTION

Cisco Optical WorkshopDWDMJanuary 31, 2004

Text of Cisco DWDM

  • 1 2001, Cisco Systems, Inc. All rights reserved. 2001, Cisco Systems, Inc. All rights reserved. 2001, Cisco Systems, Inc. All rights reserved.

    Cisco Optical WorkshopDWDM

    January 31, 2004

  • 2001, Cisco Systems, Inc. All rights reserved. 2 2001, Cisco Systems, Inc. All rights reserved. 2 2001, Cisco Systems, Inc. All rights reserved. 2

    Agenda

    Introduction Components Forward Error Correction DWDM Design Summary

  • 2001, Cisco Systems, Inc. All rights reserved. 3 2001, Cisco Systems, Inc. All rights reserved. 3 2001, Cisco Systems, Inc. All rights reserved. 3

    Increasing Network Capacity OptionsSame bit rate, more fibersSlow Time to MarketExpensive EngineeringLimited Rights of WayDuct Exhaust

    More Fibers(SDM)

    Same fiber & bit rate, more sFiber CompatibilityFiber Capacity ReleaseFast Time to MarketLower Cost of OwnershipUtilizes existing TDM Equipment

    WDM

    Faster Electronics(TDM)

    Higher bit rate, same fiberElectronics more expensive

  • 2001, Cisco Systems, Inc. All rights reserved. 4 2001, Cisco Systems, Inc. All rights reserved. 4 2001, Cisco Systems, Inc. All rights reserved. 4

    Fiber Networks

    Single Single Fiber (One Fiber (One

    Wavelength)Wavelength)

    Channel 1

    Channel n

    Time division multiplexingSingle wavelength per fiberMultiple channels per fiber4 OC-3/STM1 channels in OC-12/STM44 OC-12/STM4 channels in OC-48/STM1616 OC-3/STM1 channels in OC-48/STM16

    Wave division multiplexingMultiple wavelengths per fiber4, 16, 24, 40 channels per systemMultiple channels per fiber

    Hybrid Networks

    Single FiberSingle Fiber(Multiple (Multiple

    Wavelengths)Wavelengths)

    l1l1l2l2

    lnln

  • 2001, Cisco Systems, Inc. All rights reserved. 5 2001, Cisco Systems, Inc. All rights reserved. 5 2001, Cisco Systems, Inc. All rights reserved. 5

    Types of WDM Traditional passive systems

    Low channel countsLess than 100km

    CWDMDefined in ITU-T G694.2Up to 18 channels with 20nm spacingTarget distances from 40km to ~100km

    DWDMSpacing of 200, 100, 50 or 25 GHzChannel counts of 32 and greaterDistances of 600km and greater

  • 2001, Cisco Systems, Inc. All rights reserved. 6 2001, Cisco Systems, Inc. All rights reserved. 6 2001, Cisco Systems, Inc. All rights reserved. 6

    DWDM History Early WDM (late 80s)

    Two widely separated wavelengths (1310, 1550nm) Second generation WDM (early 90s)

    Two to eight channels in 1550 nm window400+ GHz spacing

    Current DWDM systems16 to 40 channels in 1550 nm window100 to 200 GHz spacingAutomatic power control schemesHybrid DWDM/TDM systems

    Next generation DWDM systems64 to 160 channels in 1550 nm window50 and 25 GHz spacing

  • 2001, Cisco Systems, Inc. All rights reserved. 7 2001, Cisco Systems, Inc. All rights reserved. 7 2001, Cisco Systems, Inc. All rights reserved. 7

    Wavelength Characteristics for DWDM

    TransparencyCan carry multiple protocols on same fiberCan carry multiple TDM channels on a wave (muxponding)Monitoring can be aware of multiple protocols

    Wavelength spacing50GHz, 100GHz, 200GHzDefines how many and which wavelengths can be used

    Wavelength capacity and bit rateExample: 1.25Gb/s, 2.5Gb/s, 10Gb/s

  • 2001, Cisco Systems, Inc. All rights reserved. 8 2001, Cisco Systems, Inc. All rights reserved. 8 2001, Cisco Systems, Inc. All rights reserved. 8

    Optical Transmission Bands

    Band Wavelength (nm)820 - 900

    1260 1360New Band 1360 1460

    S-Band 1460 1530C-Band 1530 1565L-Band 1565 1625U-Band 1625 1675

  • 2001, Cisco Systems, Inc. All rights reserved. 9 2001, Cisco Systems, Inc. All rights reserved. 9 2001, Cisco Systems, Inc. All rights reserved. 9

    Fiber Attenuation Characteristics

    800 900 1000 1100 1200 1300 1400 1500 1600

    Wavelength in Nanometers (nm)

    0.2 dB/Km

    0.5 dB/Km

    2.0 dB/Km

    Attenuation vs. WavelengthAttenuation vs. Wavelength S-Band:14601530nmL-Band:15651625nm

    C-Band:15301565nm

    Fibre Attenuation Curve

  • 2001, Cisco Systems, Inc. All rights reserved. 10 2001, Cisco Systems, Inc. All rights reserved. 10 2001, Cisco Systems, Inc. All rights reserved. 10

    Agenda

    Introduction Components Forward Error Correction DWDM Design

  • 2001, Cisco Systems, Inc. All rights reserved. 11 2001, Cisco Systems, Inc. All rights reserved. 11 2001, Cisco Systems, Inc. All rights reserved. 11

    DWDM Components123

    1...n15xx850/1310

    TransponderOptical Multiplexer

    Optical Add/Drop Multiplexer(OADM)

    (Band and Channel)

    123

    1...n 123

    Optical De-multiplexer

  • 2001, Cisco Systems, Inc. All rights reserved. 12 2001, Cisco Systems, Inc. All rights reserved. 12 2001, Cisco Systems, Inc. All rights reserved. 12

    More DWDM Components

    Optical Amplifier(EDFA)

    Optical AttenuatorVariable Optical Attenuator

    Dispersion Compensator (DCM / DCU)

  • 2001, Cisco Systems, Inc. All rights reserved. 13 2001, Cisco Systems, Inc. All rights reserved. 13 2001, Cisco Systems, Inc. All rights reserved. 13

    Typical DWDM Network Architecture

    DWDM SYSTEM DWDM SYSTEM

    VOA EDFA DCM

    VOAEDFADCM

    Service Mux(Muxponder)

    Service Mux(Muxponder)

  • 2001, Cisco Systems, Inc. All rights reserved. 14 2001, Cisco Systems, Inc. All rights reserved. 14 2001, Cisco Systems, Inc. All rights reserved. 14

    Transponders

    Converts broadband optical signals to a specific wavelength via optical to electrical to optical conversion (O-E-O)

    Used when Optical LTE (Line Termination Equipment) does not have tight tolerance ITU optics

    Performs 2R or 3R regeneration function Receive Transponders perform reverse function

    Low Cost IR/SR Optics

    Wavelengths Converted

    1

    OEO

    OEO

    OEO

    2

    n

    From Optical OLTE

    To DWDM Mux

  • 2001, Cisco Systems, Inc. All rights reserved. 15 2001, Cisco Systems, Inc. All rights reserved. 15 2001, Cisco Systems, Inc. All rights reserved. 15

    Performance Monitoring

    Performance monitoring performed on a per wavelength basis through transponder

    G.709 based No modification of overhead Data transparency is preserved

  • 2001, Cisco Systems, Inc. All rights reserved. 16 2001, Cisco Systems, Inc. All rights reserved. 16 2001, Cisco Systems, Inc. All rights reserved. 16

    Laser Characteristics Non DWDM Laser

    Fabry Perot DWDM Laser

    Distributed Feedback (DFB)

    Power c

    cPower

    Dominant single laser line Tighter wavelength control

    Spectrally broad Unstable center/peak wavelength

    Active medium

    MirrorPartially transmitting

    Mirror

    Amplified light

  • 2001, Cisco Systems, Inc. All rights reserved. 17 2001, Cisco Systems, Inc. All rights reserved. 17 2001, Cisco Systems, Inc. All rights reserved. 17

    Transponder: Direct vs. External ModulationDirect Modulation External Modulation

    Electrical Signal in

    Electrical Signal in

    IinDC Iin

    Mod. Optical Signal

    Optical Signal out

    CW UnmodulatedOptical Signal

    External Modulator

    Simple approach Low cost Client side Metro WDM

    Extra components Higher cost WDM side LH WDM

    Ex: 1800 ps/nm Dispersion Tolerance Ex: 10,000 ps/nm Dispersion Tolerance

  • 2001, Cisco Systems, Inc. All rights reserved. 18 2001, Cisco Systems, Inc. All rights reserved. 18 2001, Cisco Systems, Inc. All rights reserved. 18

    DWDM Receiver Requirements

    I

    Receivers Common to all Transponders Not Specific to wavelength (Broadband) PIN photodiodes

    Simple and fast Avalanche photodiodes (APD)

    Slower, but better sensitivityBetter receiver

  • 2001, Cisco Systems, Inc. All rights reserved. 19 2001, Cisco Systems, Inc. All rights reserved. 19 2001, Cisco Systems, Inc. All rights reserved. 19

    Optical Amplifier

    Pout = GPinPinGG

    EDFA amplifiers Separate amplifiers for C-band and L-band Source of optical noise

  • 2001, Cisco Systems, Inc. All rights reserved. 20 2001, Cisco Systems, Inc. All rights reserved. 20 2001, Cisco Systems, Inc. All rights reserved. 20

    OA Gain and Fiber Loss

    OA Gain

    TypicalFiber Loss

    4 THz

    25 THz

    OA gain is centered in 1550 window OA bandwidth is less than fiber bandwidth

  • 2001, Cisco Systems, Inc. All rights reserved. 21 2001, Cisco Systems, Inc. All rights reserved. 21 2001, Cisco Systems, Inc. All rights reserved. 21

    Erbium Doped Fiber Amplifier

    Isolator Isolator

    PumpLaserPumpLaser

    Coupler Coupler

    Erbium-DopedFiber (1050m)

    PumpLaserPumpLaser

    Simple device consisting of four parts: Erbium-doped fiber An optical pump (to invert the population). A coupler An isolator to cut off backpropagating noise

  • 2001, Cisco Systems, Inc. All rights reserved. 22 2001, Cisco Systems, Inc. All rights reserved. 22 2001, Cisco Systems, Inc. All rights reserved. 22

    Principles of Er3+ Emission

    980nmSource

    1480nmSource

    E0

    EM (~10msec)

    ~1usec

    Stimulated Emission(15201620 nm)

    EH

    SIGNAL PHOTON1550 nm

    PUMPPHOTON

  • 2001, Cisco Systems, Inc. All rights reserved. 23 2001, Cisco Systems, Inc. All rights reserved. 23 2001, Cisco Systems, Inc. All rights reserved. 23

    Optical Signal-to Noise Ratio (OSNR)

    Ratio of signal power to noise OSNR = 10 log10(Ps/Pn) Large OSNR is better OSNR reduced at each amplifier

    Signal Level

    Noise Level

    X dB

    EDFA SchematicEDFA Schematic

    (OSNR)out(OSNR)in

    NFPin

  • 2001, Cisco Systems, Inc. All rights reserved. 24 2001, Cisco Systems, Inc. All rights reserved. 24 2001, Cisco Systems, Inc. All rights reserved. 24

    1550nm Output

  • 2001, Cisco Systems, Inc. All rights reserved. 25 2001, Cisco Systems, Inc. All rights reserved. 25 2001, Cisco Systems, Inc. All rights reserved. 25

    1550nm with 15db Attenuator

  • 2001, Cisco Systems, Inc. All rights reserved. 26 2001, Cisco Systems, Inc. All rights reserved. 26 2001, Cisco Systems, Inc. All rights reserved. 26

    EDFA with No Input Signal

  • 2001, Cisco Systems, Inc. All rights reserved. 27 2001, Cisco Systems, Inc. All rights reserved. 27 2001, Cisco Systems, Inc. All rights reserved. 27

    EDFA Output with 1550nm Input

  • 2001, Cisco Systems, Inc. All rights reserved. 28 2001, Cisco Systems, Inc. All rights reserved. 28 2001, Cisco Systems, Inc. All rights reserved. 28

    Loss Management: LimitationsErbium Doped Fiber Amplifier

    Each amplifier adds noise, thus the optical SNR decreases gradually along the chain; we can have only have a finite number of amplifiers and spans and eventually electrical regeneration will be necessary

    Gain flatness is another key parameter mainly for long amplifier chains

    Each EDFA at the Output Cuts at Least in a Half (3dB) the OSNR Received at the Input

    Noise Figure > 3 dBTypically between 4 and 6

    Noise Figure > 3 dBTypically between 4 and 6

  • 2001, Cisco Systems, Inc. All rights reserved. 29 2001, Cisco Systems, Inc. All rights reserved. 29 2001, Cisco Systems, Inc. All rights reserved. 29

    Optical Thin Film Filter Technology

    Dielectric Filter1,2,3,...n

    2 1, ,3,...n

    Thin Film Filter (TFF) Dielectric material on substrate Photons of a specific wavelength pass through Others are reflected Integrated to demux multiple wavelengths

  • 2001, Cisco Systems, Inc. All rights reserved. 30 2001, Cisco Systems, Inc. All rights reserved. 30 2001, Cisco Systems, Inc. All rights reserved. 30

    Fiber Bragg Gratings

    Core Cladding

    Refractive Index Changes

    Small section of fiber modified by UV exposure Creates periodic changes in refractive index Light of a specific wavelength is refracted then reflected back Wavelength is determined by refractive index change and

    distance between refraction changes

  • 2001, Cisco Systems, Inc. All rights reserved. 31 2001, Cisco Systems, Inc. All rights reserved. 31 2001, Cisco Systems, Inc. All rights reserved. 31

    Multiplexer / Demultiplexer

    DWDMDemux

    Wavelengths Converted via Transponders

    Wavelength Multiplexed Signals

    DWDMMux

    Wavelength Multiplexed Signals

    Wavelengths separated into individual ITU Specific lambdas Loss of power for each Lambda

  • 2001, Cisco Systems, Inc. All rights reserved. 32 2001, Cisco Systems, Inc. All rights reserved. 32 2001, Cisco Systems, Inc. All rights reserved. 32

    Optical Add/Drop Filters (OADMs)

    OADMs allow flexible add/drop of channels

    Drop Channel

    Add Channel

    Drop & Insert

    Pass Through loss and Add/Drop loss

  • 2001, Cisco Systems, Inc. All rights reserved. 33 2001, Cisco Systems, Inc. All rights reserved. 33 2001, Cisco Systems, Inc. All rights reserved. 33

    Agenda

    Introduction Components Forward Error Correction DWDM Design Summary

  • 2001, Cisco Systems, Inc. All rights reserved. 34 2001, Cisco Systems, Inc. All rights reserved. 34 2001, Cisco Systems, Inc. All rights reserved. 34

    Transmission Errors

    Errors happen in the real world Large BW-delay products in tranport systems Bursty appearance rather than distributed Noisy medium (ASE, distortion, PMD) TX/RX instability (spikes, current surges) Detect is good, correct is better

    Transmitter ReceiverTransmission

    Channel

    Information InformationNoise

  • 2001, Cisco Systems, Inc. All rights reserved. 35 2001, Cisco Systems, Inc. All rights reserved. 35 2001, Cisco Systems, Inc. All rights reserved. 35

    Forward Error Correction

    Error correcting codes both detect errors and correct them

    Forward Error Correction (FEC) is a systemadds additional information to the data streamcorrects eventual errors that are caused by the transmission system.

    Low BER achievable on noisy medium Increases system capability coding gain

    Trade off BER vs. distance

  • 2001, Cisco Systems, Inc. All rights reserved. 36 2001, Cisco Systems, Inc. All rights reserved. 36 2001, Cisco Systems, Inc. All rights reserved. 36

    Errors

    Symbol error occursIf one bit in a symbol is wrongOr if all bits in a symbol are wrong

    RS(255, 239) can correct 8 symbol errors8 single bit errors each in a separate byte

    8 bits corrected8 complete byte errors

    8 x 8 = 64 bits corrected

    Can detect up to 2t errors Well suited for handling burst errors

  • 2001, Cisco Systems, Inc. All rights reserved. 37 2001, Cisco Systems, Inc. All rights reserved. 37 2001, Cisco Systems, Inc. All rights reserved. 37

    Reed-Solomon Codes

    Linear block codes (subset of BCH codes) Specified as RS(n,k) with s-bit symbols Encoder

    Takes k data symbols of s bits eachAdds parity symbols to make an n symbol codewordYields n-k parity symbols of s bits each

    DecoderCorrects up to t symbols that contain errors in the codewordWhere 2t = n-k

  • 2001, Cisco Systems, Inc. All rights reserved. 38 2001, Cisco Systems, Inc. All rights reserved. 38 2001, Cisco Systems, Inc. All rights reserved. 38

    RS(255, 239) Example

    8-bit symbols (i.e. byte) 255 byte codeword 239 data bytes 16 parity bytes n = 255, k = 239, s = 8

    2t = 16, t = 8 Errors in up to 8 bytes

    anywhere in the codeword corrected automatically

    k = 239 2t = 16n = 255

    ParityParityDataData

  • 2001, Cisco Systems, Inc. All rights reserved. 39 2001, Cisco Systems, Inc. All rights reserved. 39 2001, Cisco Systems, Inc. All rights reserved. 39

    G.709 FEC

    RS(255,239)239 data bytes + 16 bytes FEC = 255 bytes

    OTU row split into 16 sub rows of 255 bytes16 x 255 = 4080 = 1 OTU row

    Sub rows processed separately FEC parity check bytes

    Calculated over 239 bytes of sub rowTransmitted in the last 16 bytes of same sub row

  • 2001, Cisco Systems, Inc. All rights reserved. 40 2001, Cisco Systems, Inc. All rights reserved. 40 2001, Cisco Systems, Inc. All rights reserved. 40

    FEC Sub-Rows

    InformationInformation ParityParityFEC sub-row #16

    FEC sub-row #1

    FEC sub-row #2

    Information bytesInformation bytes Parity check bytesParity check bytesOTU Row

    InformationInformation ParityParity

    InformationInformation ParityParity

    1, 2 ...16 3824 3825, 3826 ... 3840 4080

    1 239 240 255

    1 239 240 255

    1 239 240 255

  • 2001, Cisco Systems, Inc. All rights reserved. 41 2001, Cisco Systems, Inc. All rights reserved. 41 2001, Cisco Systems, Inc. All rights reserved. 41

    FEC Performance, Theoretical

    FEC gain 6.3 dB @ 10-15 BER

    Received Opticalpower (dBm)

    Bit Error Rate

    10-30

    10-10

    -46 -44 -42 -40 -38

    1

    10-20

    -36 -34 -32

    BER without FEC

    BER with FEC

    Coding Gain

    BER floor

  • 2001, Cisco Systems, Inc. All rights reserved. 42 2001, Cisco Systems, Inc. All rights reserved. 42 2001, Cisco Systems, Inc. All rights reserved. 42

    FEC in DWDM Systems

    FEC implemented on transponders (TX, RX, 3R) No change on the rest of the system

    IP

    SDH

    ATM

    .

    .

    FEC

    FEC

    FEC

    2.48 G 2.66 G

    9.58 G 10.66 G

    IP

    SDH

    ATM

    9.58 G 10.66 G

    .

    .

    FEC

    FEC

    FEC

    2.66 G 2.48 G

  • 2001, Cisco Systems, Inc. All rights reserved. 43 2001, Cisco Systems, Inc. All rights reserved. 43 2001, Cisco Systems, Inc. All rights reserved. 43

    Agenda

    Introduction Components Forward Error Correction DWDM Design Summary

  • 2001, Cisco Systems, Inc. All rights reserved. 44 2001, Cisco Systems, Inc. All rights reserved. 44 2001, Cisco Systems, Inc. All rights reserved. 44

    DWDM Design Topics

    DWDM Challenges Unidirectional vs. Bidirectional Protection Capacity Distance

  • 2001, Cisco Systems, Inc. All rights reserved. 45 2001, Cisco Systems, Inc. All rights reserved. 45 2001, Cisco Systems, Inc. All rights reserved. 45

    Transmission Effects Attenuation:

    Reduces power level with distance

    Dispersion and nonlinear effects: Erodes clarity with distance and speed

    Noise and Jitter:Leading to a blurred image

  • 2001, Cisco Systems, Inc. All rights reserved. 46 2001, Cisco Systems, Inc. All rights reserved. 46 2001, Cisco Systems, Inc. All rights reserved. 46

    Solution for Attenuation

    OpticalAmplification

    OpticalAmplificationLossLoss

    OA

  • 2001, Cisco Systems, Inc. All rights reserved. 47 2001, Cisco Systems, Inc. All rights reserved. 47 2001, Cisco Systems, Inc. All rights reserved. 47

    Solution For Chromatic Dispersion

    Saw ToothCompensationSaw ToothCompensationDispersionDispersion

    Dispersion

    Length

    +D -DTotal dispersion averages to ~ zero

    Fiber spool Fiber spoolDCU DCU

  • 2001, Cisco Systems, Inc. All rights reserved. 48 2001, Cisco Systems, Inc. All rights reserved. 48 2001, Cisco Systems, Inc. All rights reserved. 48

    Uni Versus Bi-directional DWDM

    DWDM systems can be implemented in two different ways

    Uni-directional:

    Uni -directional

    1 3 5 7 Fiber

    Fiber 1 3 5 7

    2 4 6 8

    2 4 6 8

    wavelengths for one direction travel within one fibertwo fibers needed for full-duplex system

    Bi-directional:a group of wavelengths for each direction single fiber operation for full-

    Bi -directional

    5 6 7 8

    Fiber

    1 2 3 4

    duplex system

  • 2001, Cisco Systems, Inc. All rights reserved. 49 2001, Cisco Systems, Inc. All rights reserved. 49 2001, Cisco Systems, Inc. All rights reserved. 49

    Uni Versus Bi-directional DWDM (cont.) Uni-directional 32 channels system

    32

    32

    Full band

    Full band

    ChannelSpacing100 GHz

    16

    16 Blue-band

    Red-band

    ChannelSpacing100 GHz

    16

    16

    Bi-directional 32 channels system

    32 chfull

    duplex

    16 chfull

    duplex

  • 2001, Cisco Systems, Inc. All rights reserved. 50 2001, Cisco Systems, Inc. All rights reserved. 50 2001, Cisco Systems, Inc. All rights reserved. 50

    Optical Protection Schemes

    Unprotected Client Protected

    Single client, single txpdr Two client ports, equipment protected Txpdr

    Splitter Protected Y-Cable Protected

    Single client, protected WDM fiber Single client port, equipment protected Txpdr

  • 2001, Cisco Systems, Inc. All rights reserved. 51 2001, Cisco Systems, Inc. All rights reserved. 51 2001, Cisco Systems, Inc. All rights reserved. 51

    1 Transponder

    1 ClientInterface

    Unprotected

    1 client & 1 trunk laser (one transponder) needed, only 1 path available

    No protection in case of fiber cut, transponder failure, client failure, etc..

  • 2001, Cisco Systems, Inc. All rights reserved. 52 2001, Cisco Systems, Inc. All rights reserved. 52 2001, Cisco Systems, Inc. All rights reserved. 52

    2 Transponders

    2 Clientinterfaces

    2 client & 2 trunk lasers (two transponders) needed, two optically unprotected paths

    Protection via higher layer protocol

    Client Protected Mode

  • 2001, Cisco Systems, Inc. All rights reserved. 53 2001, Cisco Systems, Inc. All rights reserved. 53 2001, Cisco Systems, Inc. All rights reserved. 53

    Only 1 client & 1 trunk laser (single transponder) needed

    Protects against Fiber Breaks

    Optical Splitter Switch

    Workinglambda

    protectedlambda

    Optical Splitter Protection

  • 2001, Cisco Systems, Inc. All rights reserved. 54 2001, Cisco Systems, Inc. All rights reserved. 54 2001, Cisco Systems, Inc. All rights reserved. 54

    2 client & 2 trunk lasers (two transponders) needed

    Increased cost & availability

    2 Transponders

    Only oneTX active

    workinglambda

    protectedlambda

    Y cable

    Line Card / Y- Cable Protection

  • 2001, Cisco Systems, Inc. All rights reserved. 55 2001, Cisco Systems, Inc. All rights reserved. 55 2001, Cisco Systems, Inc. All rights reserved. 55

    Designing for Capacity

    Distance

    SolutionSpaceB i

    t

    R

    a

    t

    e

    Wavelengths

    Goal is to maximize transmission capacity and system reach

    Figure of merit is Gbps KmLong-haul systems push the envelopeMetro systems are considerably simpler

  • 2001, Cisco Systems, Inc. All rights reserved. 56 2001, Cisco Systems, Inc. All rights reserved. 56 2001, Cisco Systems, Inc. All rights reserved. 56

    Designing for Distance

    Amplifier SpacingG = Gain of AmplifierS

    Pout

    Pnoise

    Pin

    D = Link Distance

    L = Fiber Loss in a Span

    Link distance (D) is limited by the minimum acceptable electrical SNR at the receiverDispersion, Jitter, or optical SNR can be limit

    Amplifier spacing (S) is set by span loss (L)Closer spacing maximizes link distance (D)Economics dictates maximum hut spacing

  • 2001, Cisco Systems, Inc. All rights reserved. 57 2001, Cisco Systems, Inc. All rights reserved. 57 2001, Cisco Systems, Inc. All rights reserved. 57

    Link Distance vs. OA Spacing

    W

    a

    v

    e

    l

    e

    n

    g

    t

    h

    C

    a

    p

    a

    c

    i

    t

    y

    (

    G

    b

    /

    s

    )

    2.5

    5

    10

    20

    2000 4000 6000 80000

    Amp Spacing60 km

    80 km

    100 km

    120 km

    140 km

    Total System Length (km)

    System cost and and link distance both depend strongly on OA spacing

  • 2001, Cisco Systems, Inc. All rights reserved. 58 2001, Cisco Systems, Inc. All rights reserved. 58 2001, Cisco Systems, Inc. All rights reserved. 58

    OEO Regeneration in DWDM Networks

    Long Haul

    OA noise and fiber dispersion limit total distance before regenerationOptical-Electrical-Optical conversionFull 3R functionality: Reamplify, Reshape, Retime

    Longer spans can be supported using back to back systems

  • 2001, Cisco Systems, Inc. All rights reserved. 59 2001, Cisco Systems, Inc. All rights reserved. 59 2001, Cisco Systems, Inc. All rights reserved. 59

    3R with Optical Multiplexor and OADM

    Express channels must be regenerated

    Two complete DWDM terminals needed

    Provides drop-and- continue functionality

    Express channels only amplified, not regenerated

    Reduces size, powerand cost

    Back-to-back DWDM

    Optical add/drop multiplexer

    7

    1234

    N

    OADM

    7

    1234

    N

    7

    1234

    N7

    1234

    N

  • 2001, Cisco Systems, Inc. All rights reserved. 60 2001, Cisco Systems, Inc. All rights reserved. 60 2001, Cisco Systems, Inc. All rights reserved. 60

    Synchronization over DWDM

    Ethernet

    GigabitEthernet

    Ethernet

    DS1T1 OC-12c

    OC-48c

    Fiber

    REGEN

    WDM

    OC-3c

    PRS

    SONETNetwork

    OC-48c

    OC-48c

    Synchronization driven from network

    Router interface timed to PRS via Rx

    SONET Network All links are asynchronous to

    each other Line synchronization

    driven from router Far end derives timing

    from line

    Point-to-Point DWDM

    ~~~~~~ ~~~~~~

  • 2001, Cisco Systems, Inc. All rights reserved. 61 2001, Cisco Systems, Inc. All rights reserved. 61 2001, Cisco Systems, Inc. All rights reserved. 61

    Network Topologies and Node Types Linear NetworkingLinear Networking

    Single SpanSingle Span

    Add/DropAdd/Drop

    TerminalTerminal TerminalTerminalOADM OADM

    (Amplified)(Amplified)OADMOADM

    (Passive)(Passive)Line Line

    AmplifierAmplifier

    OSCOSC

    TerminalTerminal TerminalTerminal

    OSCOSC

  • 2001, Cisco Systems, Inc. All rights reserved. 62 2001, Cisco Systems, Inc. All rights reserved. 62 2001, Cisco Systems, Inc. All rights reserved. 62

    Network Topologies and Node Types

    Ring NetworkingRing NetworkingOpen Ring (multiOpen Ring (multi--hub)hub)

    Hub Hub (full mux/(full mux/demuxdemux))

    Hub Hub (full mux/(full mux/demuxdemux))

    Closed RingClosed RingOADM OADM

    (Amplified, (Amplified, AntiAnti--ASE)ASE)

    Open Ring (single hub)Open Ring (single hub)Hub Hub

    (full mux/(full mux/demuxdemux))

    OADMOADM(Passive)(Passive)

    Line Line AmplifierAmplifier

    OADM OADM (Amplified)(Amplified)

    OADM OADM (Amplified)(Amplified)

    OADMOADM(Passive)(Passive)

    OADM OADM (Amplified)(Amplified)

    OSCOSC

  • 2001, Cisco Systems, Inc. All rights reserved. 63 2001, Cisco Systems, Inc. All rights reserved. 63 2001, Cisco Systems, Inc. All rights reserved. 63

    Agenda

    Introduction Components Forward Error Correction DWDM Design Summary

  • 2001, Cisco Systems, Inc. All rights reserved. 64 2001, Cisco Systems, Inc. All rights reserved. 64 2001, Cisco Systems, Inc. All rights reserved. 64

    DWDM Benefits

    DWDM systems provide hundreds of Gbps of scalable transmission capacity today

    Protocol and bit rate transparency Provides capacity beyond TDMs capability Less fiber deployment Less hardware deployment Supports incremental, modular growth

  • F0_5585_c2 65 1999, Cisco Systems, Inc.

    Cisco Optical WorkshopDWDMJanuary 31, 2004AgendaIncreasing Network Capacity OptionsFiber NetworksTypes of WDMDWDM HistoryWavelength Characteristics for DWDMOptical Transmission BandsFiber Attenuation CharacteristicsAgendaDWDM ComponentsMore DWDM ComponentsTypical DWDM Network ArchitectureTranspondersPerformance MonitoringLaser CharacteristicsTransponder: Direct vs. External ModulationDWDM Receiver RequirementsOptical AmplifierOA Gain and Fiber LossErbium Doped Fiber AmplifierPrinciples of Er3+ Emission1550nm Output1550nm with 15db AttenuatorEDFA with No Input SignalEDFA Output with 1550nm InputLoss Management: LimitationsErbium Doped Fiber AmplifierOptical Thin Film Filter TechnologyFiber Bragg GratingsMultiplexer / DemultiplexerOptical Add/Drop Filters (OADMs)AgendaTransmission ErrorsForward Error CorrectionErrorsReed-Solomon CodesRS(255, 239) ExampleG.709 FECFEC Sub-RowsFEC Performance, TheoreticalFEC in DWDM SystemsAgendaDWDM Design TopicsTransmission EffectsSolution for AttenuationSolution For Chromatic DispersionUni Versus Bi-directional DWDMUni Versus Bi-directional DWDM (cont.)Optical Protection SchemesUnprotectedClient Protected ModeOptical Splitter ProtectionLine Card / Y- Cable ProtectionDesigning for CapacityDesigning for DistanceLink Distance vs. OA SpacingOEO Regeneration in DWDM Networks3R with Optical Multiplexor and OADMSynchronization over DWDMNetwork Topologies and Node TypesNetwork Topologies and Node TypesAgendaDWDM Benefits