Lecture: 9 Elastic Optical Networks

Ajmal Muhammad, Robert ForchheimerInformation Coding Group

ISY Department

Outline

Motivation Elastic Optical Networking

Flexible spectrum grid, tunable transceiver, flexible OXC Flexible Optical Nodes Routing and Spectrum Assignment Problem

Research Motivation

Emerging applications with a range of transport requirementFuture applications with unknown requirementsFlexible and efficient optical networks to support existing, emerging and future applications

Courtesy: High performance networklab., Bristol

High-speed data 400G, 1Tb/s

Media

Applications with Diverse Requirements

Courtesy: High performance networklab., Bristol

Evolution of Transmission Capacity

Spectral Efficiency (SE) ImprovementFixed optical amplifier bandwidth (~ 5 THz)

Per fiber capacity increase has been accomplished through boosting SE (bit rate, wavelength, symbol per bit, state of polarization)

Bit loading higher than that for DP-QPSK causes rapid increase in SNR penalty, and results in shorter optical reachSE improvement is slowing down, meaning higher rate data need more spectrum

0.01

0.1

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0 100 200 300 400 5000.01

0.1

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Bit rate per channel (Gb/s)

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Spe

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DP-QPSK

DP-16QAM

DP-64QAM

DP-256QAM

DP-1024QAM

QPSKBPSK

600

@25 Gbaud

Optical amplifier bandwidth (~ 5 THz)

TDM

WDM

Multiplexing technology evolutionPDM

Multi-level mod.

Current Optical Networks :: Inflexible

Super-wavelength

Courtesy: High performance networklab., Bristol

Current Solution for Bandwidth-Intensive Applications

Optical virtual concatenation (OVC) for high capacity end-to-end connection (super-wavelength)

Demultiplex the demand to smaller ones such as 100 or 40 Gb/s, which can still fit in the fixed grid (Inverse multiplexing)

Several wavelengths are grouped and allocated end-to-end according to the application bandwidth requirements

Grouping occurs at the client layer without really affecting the network

Connection over several wavelengths is not switched as a single entity in network nodes

Elastic Optical NetworkingThe term elastic refers to three key properties:The optical spectrum can be divided up flexibly

Courtesy: Ori Gerstel, IEEE Comm. Mag. 2012

Elastic TransceiversThe transceivers can generate elastic optical paths (EOPs); that is path with variable bit rates

Tunable transceiver Courtesy: Steven Gringeri, IEEE Comm. Mag. 2013

Flexible Switching

EONs

WDM Networks Bandwidth Variable

The optical nodes (cross-connect) need to support a wide range of switching (i.e., varying from sub-wavelength to super-wavelength)

Drivers for Developing the EONs Support for 400 Gb/s, 1Tb/s and other high bit rate demands

Disparate bandwidth needs: properly size the spectrum for each demand based on its bit rate & the transmission distance

Tighter channel spacing: freeing up spectrum for other demands Reach vs. spectral efficiency trade-off: bandwidth variable transmitter can adjust to a modulation format occupying less optical spectrum for short EOP and still perform error-free due to the reduced impairments

Dynamic networking: the optical layer can now response directly to variable bandwidth demands from the client layers

Elastic Optical Path Network:: Example

Elastic channelspacing

250 km 250 km

400 Gb/s 200 Gb/s 400 Gb/s100 Gb/s 100 Gb/s

1,000 km 1,000 km 1,000 km

Fixed format, grid

Adaptive modulation

QPSKQPSK200 Gb/s QPSK 16QAM 16QAM

Path length

Bit rate

Conventional design

Elastic optical path network

Outline

Motivation Elastic Optical Networking

Flexible spectrum grid, tunable transceiver, flexible OXC Flexible Optical Nodes Routing and Spectrum Assignment Problem

Common Building Blocks for Flexible OXCs

Reconfigurable Optical Add-Drop Multiplexer (ROADM)

Add channels Drop channels

Optical splitter Wavelength selective switch

Multi-Granular Optical Switching

FXC: Fiber switch

BXC: Waveband switch

WXC: Wavelength switch

BTF: Band to Fiber

Add channels Drop channels

Architecture on Demand (AoD)

Optical backplane cross-connections for AoD OXCs

MEMS switch is used to interconnected all theInput-output ports and switching devices

Courtesy: High performance networklab., Bristol

AoD NodeAimed to develop an optical node that can adapt its architecture according to the traffic profile and support elastic allocation of resources

Flexible OXC ConfigurationBackplane implemented with 96x96 3D-MEMSFlexibility to implement and test several switch architectures on-the-flySwitching time 20ms

Courtesy: High performance networklab., Bristol

Outline

Motivation Elastic Optical Networking

Flexible spectrum grid, tunable transceiver, flexible OXC Flexible Optical Nodes Routing and Spectrum Assignment Problem

Routing and Spectrum Assignment (RSA)

Spectrum variable (non-constant)connections, in contrast to standardWDM

Planning Elastic/Flexgrid Networks

Input: Network topology, traffic matrix, physical layer modelsOutput: Routes and spectrum allocation RSA(RMLSA include also the modulation-level used – 2 flexibility degree: modulation and spectrum)

Minimize utilized spectrum and/or number of transponders, and/or… Satisfy physical layer constraints

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Examples

RMLSA RSA

Courtesy: Ori Gerstel, IEEE Comm. Mag. 2012

Cost-Efficient Elastic Networks Planning Using AoD Nodes

Conventional ROADMs AoD ROADMs