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TRANSCRIPT
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Contents for this PresentationSDH/DWDMSDH/DWDMSDH/DWDMSDH/DWDMbasedbased
Multi-ServiceTransport
PlatformPlatform
by
Khurram Shahzadu a S a ad
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Contents for this PresentationBrief Description of the Project
Development of a Unified Transport Platform facilitating multiple services Platform facilitating multiple services like POTS, PDH, SDH, ATM, IP, CATV, HDTV, B-ISDN, Ethernet and Giga-bit Ethernet to Residential Areas Business Ethernet to Residential Areas, Business Groups, Enterprise Groups and InternetServices Centers etc.
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Contents for this PresentationContents for this Lecture
Optical Communications
Why Move to DWDM?and DWDM Systems
Why Move to DWDM? Optical Transmission Systemp y
a. Advantages and Limitsb. Fiber Characteristics
DWDMa. Overviewc. Fiber Propagation Modesd. Optical Transmitters (LEDs, Lasers)
O ti l R i (Ph t di d Ph t t i t )
b. Application Modesc. Laser Modulation Modesd DWDM C t
Multi-Service Transport Platforme. Optical Receivers (Photodiodes, Phototransistors)f. Optical Devices (Amplifiers, Splitters, Couplers,
Filters and Switches)
d. DWDM Componentse. Network Elements (OTM, OADM, OLA, REG)f System EngineeringFilters and Switches)f. System Engineering
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Contents for this PresentationWhy Move to DWDM
The optical fiber is the best medium to bedeployed at backbones of very high data rates.deployed at backbones of very high data rates.In order to increase the bandwidth, SDM isused by laying more and more fibers but meanused by laying more and more fibers but meanwhile an enormous amount of bandwidth offib i b i t d I d t tili thfiber is being wasted. In order to utilize themaximum bandwidth, DWDM is the only, ysolution.
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Contents for this PresentationOptical Transmission System
Optical Communication SystemOptical Communication System
Basic principle of light transmissionon Optical Fiberon Optical Fiber
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Contents for this PresentationAdvantages of Optical System
Weight and size less than copper cable Weight and size less than copper cable Material cost is almost same Huge information capacity No Electrical connection No Electrical connection No Electromagnetic Interference More distance between Regenerators Better security due to immediate Better security due to immediate
failure detection
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Contents for this PresentationLimitations
L d t bl j i i ( db j i ) Loss due to cable joining (1 db/joint)
Bending of fiber should not exceedgthe limit
Optics for transmission only due to Optics for transmission only due to unavailability of optical amplifiers
Gamma radiation can cause interference and also it cause to interference and also it cause to discolor glass that cause attenuation
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Contents for this PresentationFiber Propagation Modes
Illustration of differentpropagation modes
Typical fiber infraredabsorption spectrumabsorption spectrum
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Contents for this PresentationHard Polymer (plastic) Clad (silica) Fiber
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Contents for this PresentationOptical Devices
O ti l T itt Optical Transmitters Optical Detectors Optical Detectors Optical Amplifiers Optical Couplers Optical Isolators Optical Isolators Optical Cross Connectsp Optical Switches
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Contents for this PresentationOptical Transmitters (Sources)( )
Light Emitting Diodes (LEDs)Light Emitting Diodes (LEDs)LASERs (Light Amplification by Stimulated
E i i f R di ti )Emission of Radiations)
10G Transmitter 40G Transmitter10G Transmitter 40G Transmitter
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Contents for this PresentationCharacteristics of LEDs
Low Cost compared to Lasersp Low Power (recently 75mW) Relatively wider spectrum produced Relatively wider spectrum produced
typically 50-100 nm Incoherent Light Incoherent Light
hence not directly coupled to fiber Digital Modulation
can operate at speed of up to 300 Mbps Analogue Modulation
response is linear with current flowp
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Contents for this PresentationCharacteristics of Lasers
Ideally have single wavelengthy g g Can be modulated very precisely
pulse length of 0.5 femto seconds Can produce relatively high power (up to kWs) High %age can be transferred into fiber (50% to 80%)
Disadvantages Much expensive than LEDs The wavelength produced depends on
characteristics of material used Amplitude modulation is difficult
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Contents for this PresentationTechnical Parameters of Lasers
Spectral Width (typically 6 to 8 nm)p ( yp y ) Line Width (discrete wavelengths in Spectral Width) Coherence Length and Coherence Time g
(typically 15 cm)Lengthc = c x Timecg c c
Power (with increase in bit rate power must be increased) Operating Wavelength p g g
(Laser is chosen according to design) Wavelength Stabilityg y Tuning range and Speeds Switching time and Modulationg
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Contents for this PresentationFabry-Perot Laser
Conceptually an LED with a pair of end mirrors.p y pMirrors create right conditions to lasing to occur.Wavelengths produced are related to the distance g pbetween mirrors.
Cl = X/2nCl – Cavity LengthCl Cavity Length - Wavelength requiredX - an arbitrary number
Principle of Fabry-Perot Laser
X an arbitrary numberN - Refractive index
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Contents for this PresentationOptical Receivers (Detectors)( )
Parameters of Optical Detectors Detector Responsivity
(Ratio of Output current to Input Optical Power)
p
(Ratio of Output current to Input Optical Power) Spectral Response Range Response time Response time Noise Characteristics
40G Optical Receiver40G Optical Receiver
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Contents for this PresentationTypes of Optical Detector
Photoconductors Photodiodes
a. Schottky-Barrier Photodiodes
Phototransistors b. Avalanche Photodiodes Practical Photoconductor Detector
S h k B i Ph di dSchottky-Barrier Photodiode
Bipolar Junction Transistor as PhototansistorAvalanche Photodiode
Bipolar Junction Transistor as Phototansistor
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Contents for this PresentationOptical Amplifiers
Advantages More reliable (no need of electrical regeneration)
Advantages
Flexibility (Independence of code format, Speed increment permissible)p p )
For WDM, electrical regenerators are not suitablesuitable(indeed Optical Amplifiers made WDM implementation possible)implementation possible)
Cost factor (due to simplicity cost is lesser)
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Contents for this PresentationOptical Amplifiers
EDFA (Erbium-doped Optical Fiber ( p pAmplifier) Praseodymium (Pr) Doped Fiber Praseodymium (Pr) Doped Fiber
Amplifier Neodymium (Nd) Doped Fiber Amplifier Plastic Fiber Amplifier Plastic Fiber Amplifier Semiconductor Optical/Laser Amplifier
(SOA/SLA) Raman Effect Amplifier Raman Effect Amplifier
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Contents for this PresentationErbium-Doped Fiber Amplifier (EDFA)
Typical Internal Light path of EDFA
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Contents for this PresentationAdvantages of EDFA
High G i High Gain Large Output Power Large Output Power Wide Operating Optical Bandwidth Polarization Independence Low Noise Factor Low Noise Factor Gain Independence to System
Bit Rate and Format
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Contents for this PresentationCharacteristics of EDFA
G i ( ti f t t i t ) Gain (ratio of output power over input power) Gain Coefficient (small signal gain/pump power) B d idth ( hi h A lifi ill t ) Bandwidth (over which Amplifier will operate) Gain Saturation (point where an increase in input power
ceases to result in increase in output power)ceases to result in increase in output power) Very little sensitivity to Polarization states
(polarization sensitivity is difference in gain of an input (polarization sensitivity is difference in gain of an input signal in one polarization to the orthogonal polarization)
Adds Noise to signal Adds Noise to signalNoise = SNR(i)/SNR(o) dB
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Contents for this PresentationGain Characteristics of EDFA
Gain curve ofTypical EDFA
Response ofcascade EDFA
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Contents for this PresentationOptical CouplersY Coupler Planar Star Coupler
F d Fib St C lFused Fiber Star Coupler
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Contents for this PresentationOptical Isolators
A Simple IsolatorOperationOperation
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Contents for this PresentationOptical Cross Connect (OXC)( )
Optical Cross Connect
OXC O tli A hit tOXC Outline Architecture
OXC using tunable laser technology
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Contents for this PresentationOptical Switches
MEMS Optical Switch TechnologyA Typical Optical Switch
being Implemented
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Contents for this PresentationOptical Filters
Peak wavelength (wavelength at which the Peak wavelength (wavelength at which thefilter attenuation is least )
Nominal Wavelength (Intended by manufacturer) Nominal Wavelength (Intended by manufacturer)
Bandwidth (Distances between edges db)
Center Wavelength (Mean wavelength betweentwo edges)
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Contents for this PresentationCoupling of Light to a Fiber
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Contents for this PresentationWavelength Division Multiplexing
Multiplexing with larger channel Multiplexing with larger channel spacing (even in different windows of
i l fib ) optical fibers) typically around 50nm
WDM functions schematics
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Contents for this PresentationDWDM Dense Wavelength Division Multiplexing
Wavelength Division Multiplexing in thesame window with smaller channelSpacing (typically less than 1nm) erSpacing (typically less than 1nm)
ulti
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Contents for this PresentationAdvantages of DWDM
• Ultra Large CapacityUltra Large Capacity• Data rate transparency• Protection of existing investment
during system upgradeduring system upgrade• Flexibility, economy and reliability
of networkingCompatibility with all optical• Compatibility with all opticalswitchingswitching
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Contents for this PresentationOptical Spectrum of DWDM Signal
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Contents for this PresentationApplication Modes of DWDM
• Open DWDMNo special requirements for multiplexNo special requirements for multiplexterminal optical interfaces (ITU-T G.957)Adopts wavelength conversion technologyAdopts wavelength conversion technology
I t t d DWDM• Integrated DWDMRequires optical signal wavelengths tomeet DWDM System specifications
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Contents for this PresentationFiber Modes for DWDM
DWDM Systems only utilize single mode fiberDWDM Systems only utilize single mode fiberas transmission media
ITU-T Standard fibers for DWDM SystemG 652 • G.652 (1310nm property optimal, dispersion un-shifted)
• G.653 (1550nm property optimal, dispersion shifted)
• G.654 (cut-off wavelength shifted, reduced attenuationat 1550nm)
• G.655 (non-zero dispersion shifted, preserves dispersionnear 1550nm)
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Contents for this PresentationLaser Modulation Modes for DWDM
Di t M d l ti (I t l M d l ti ) Direct Modulation (Internal Modulation)Light wave intensity is changed bycontrolling the injection current usingLaser Diodes
Indirect Modulation (External Modulation) Indirect Modulation (External Modulation)Laser is modulated indirectly by addingan external modulator in its output pathan external modulator in its output pathto modulate the light wave
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Contents for this PresentationExternal Modulators
Constant LightSource
OpticalModulator
Optical SignalOutput
Electric Modulation Signal Input
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Contents for this PresentationDirect Modulation vs. Indirect Modulation
Simple Structure Complex StructureSimple Structure Complex Structure
Low Loss High Loss
Low Cost High Cost
High Modulation Chirp Low Modulation Chirp
T i i Di t T i i Di tTransmission Distance < 100Km
Transmission Distance> 100Km
Data Rate < 2.5G Data Rate > 2.5G
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Contents for this PresentationNetwork Element Types of DWDM
Optical Terminal Multiplexer Optical Terminal Multiplexer (OTM)
Optical Add/Drop Multiplexer (OADM)(OADM)
Optical Line Amplifier (OLA)
Regenerators Regenerators (REG)(REG)
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Contents for this PresentationNetwork Element Types of DWDM
Source: Bookham Technologies, 2002
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Contents for this PresentationOTM Signal Flow
W WA ARI
S
PA
WCR
D16
RO
MM
RI
SCA
SDHSystem
SC1 A
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WB
M16
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MTO
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Contents for this PresentationOADM Signal Flow
WCR WCT
WA WA
MR 4
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A
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SCA
SC2
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WCT WCRWCT WCR
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Contents for this PresentationRemotely Configurable OADMs
Marconi CommunicationsPMA32 R-OADM
Photonic R-OADM Architecture
PMA32 R-OADM
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Contents for this PresentationDWDM Component Requirements
Enough multiplexing channelsg p g
Low insertion loss
Large crosstalk attenuation Large crosstalk attenuation
Wide pass band Wide pass band
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Contents for this PresentationOLA Signal Flow
WARIW
A
S
PARO
RI
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BA
TOM M
SCA
SC2
RM1
TM1
SCA
TM2
RM2A
WB
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AMTO AM
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Contents for this PresentationOptical System Engineering
Determining the width and spacing ofg p gwavebands
Stabilizing the wavelength of wavelength Stabilizing the wavelength of wavelengthsensitive components
Filter alignment in cascades of filters Filter alignment in cascades of filters Control of non-linear effects Control of dispersion Control of cross-talk Dynamics of optical amplifiers Control of system noise (especially ASE) Control of system noise (especially ASE)
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Contents for this PresentationDWDM Networking Parameters
Di i Li it d Di t Dispersion Limited Distance
Power
Signal to Noise Ratio
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Contents for this PresentationDWDM Protection Mechanism
No protection available to the networkNo protection available to the networkat DWDM Layery
Reasons for unavailability of protectionReasons for unavailability of protection
Cost Cost Optical Switches C fli t b t t l f Conflict between protocols of
underlying networks
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Contents for this Presentation4 x 2.5G/DWDM Ring
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Contents for this PresentationMulti-Service Transport Platform
Multi-rate multi-service multi-service open interfacesp Flexible bandwidth allocation for• PCM (Pulse Coded Modulation) digital channels
• ATM (Asynchronous Transfer Mode)( y )• IP (Internet Protocol)
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Contents for this PresentationAvailable Interfaces for MSTP
10M Eth t 10M Ethernet
Gigabit Ethernet
100M Ethernet
ATM Gigabit Ethernet
STM-1
ATM
STM-4 STM 1
STM-16
STM 4
STM-64
E1 E3
POS (Packets over SDH) PDH
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Contents for this PresentationSDH and IP over DWDM
SimplifiedDiDiagramShowingSDH and IPTraffic overTraffic overDWDMSystemSystem
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Contents for this PresentationSimplified Transport Hierarchy
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Contents for this PresentationTechnology Layers of Transport Network
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Contents for this PresentationAn Illustration of Metro Networks
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Contents for this PresentationConclusions
Foreseeing the ever increasing bandwidthg gdemands of the world it is inevitable to usethe fiber and specifically move up to DWDMthe fiber and specifically move up to DWDMSystem
To have a unified platform supporting all the To have a unified platform supporting all thecurrent available services it is unavoidableto utilize the metro solution
In the near future we are aiming to have thegbandwidth of 100Tbps using this DWDMtechnologytechnology
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Contents for this Presentation