Contents for this PresentationSDH/DWDMSDH/DWDMSDH/DWDMSDH/DWDMbasedbased

Multi-ServiceTransport

PlatformPlatform

by

Khurram Shahzadu a S a ad

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.

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

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.

Contents for this PresentationOptical Transmission System

Optical Communication SystemOptical Communication System

Basic principle of light transmissionon Optical Fiberon Optical Fiber

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

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

Contents for this PresentationFiber Propagation Modes

Illustration of differentpropagation modes

Typical fiber infraredabsorption spectrumabsorption spectrum

Contents for this PresentationHard Polymer (plastic) Clad (silica) Fiber

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

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

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

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

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

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

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

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

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)

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

Contents for this PresentationErbium-Doped Fiber Amplifier (EDFA)

Typical Internal Light path of EDFA

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

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

Contents for this PresentationGain Characteristics of EDFA

Gain curve ofTypical EDFA

Response ofcascade EDFA

Contents for this PresentationOptical CouplersY Coupler Planar Star Coupler

F d Fib St C lFused Fiber Star Coupler

Contents for this PresentationOptical Isolators

A Simple IsolatorOperationOperation

Contents for this PresentationOptical Cross Connect (OXC)( )

Optical Cross Connect

OXC O tli A hit tOXC Outline Architecture

OXC using tunable laser technology

Contents for this PresentationOptical Switches

MEMS Optical Switch TechnologyA Typical Optical Switch

being Implemented

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)

Contents for this PresentationCoupling of Light to a Fiber

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

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

plex

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Monitor Points

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n-1NT

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ConverterConverter

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

Contents for this PresentationOptical Spectrum of DWDM Signal

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

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)

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

Contents for this PresentationExternal Modulators

Constant LightSource

OpticalModulator

Optical SignalOutput

Electric Modulation Signal Input

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

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)

Contents for this PresentationNetwork Element Types of DWDM

Source: Bookham Technologies, 2002

Contents for this PresentationOTM Signal Flow

W WA ARI

S

PA

WCR

D16

RO

MM

RI

SCA

SDHSystem

SC1 A

M

RM

TMA

WB

M16

WCT

A

RO

M

TO ATRO

MTO

Contents for this PresentationOADM Signal Flow

WCR WCT

WA WA

MR 4

S

WPA

A

RORI

S

WBA

TOM M

MR 4

SCA

SC2

RM1

TM1

SC

TM2

RM2A

WB

2A A

WP

A

RORI

MR 4BAMTO

PA

M

MR 4

WCT WCRWCT WCR

Contents for this PresentationRemotely Configurable OADMs

Marconi CommunicationsPMA32 R-OADM

Photonic R-OADM Architecture

PMA32 R-OADM

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

Contents for this PresentationOLA Signal Flow

WARIW

A

S

PARO

RI

S

BA

TOM M

SCA

SC2

RM1

TM1

SCA

TM2

RM2A

WB

2A A

WP

A

ROM

RI

AMTO AM

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)

Contents for this PresentationDWDM Networking Parameters

Di i Li it d Di t Dispersion Limited Distance

Power

Signal to Noise Ratio

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

Contents for this Presentation4 x 2.5G/DWDM Ring

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)

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

Contents for this PresentationSDH and IP over DWDM

SimplifiedDiDiagramShowingSDH and IPTraffic overTraffic overDWDMSystemSystem

Contents for this PresentationSimplified Transport Hierarchy

Contents for this PresentationTechnology Layers of Transport Network

Contents for this PresentationAn Illustration of Metro Networks

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

Contents for this Presentation