Lecture: 9 Elastic Optical Networks Ajmal Muhammad, Robert Forchheimer Information 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 requirement Future applications with unknown requirements Flexible and efficient optical networks to support existing, emerging and future applications Courtesy: High performance network lab., Bristol

High-speed data 400G, 1Tb/s Media Applications with Diverse Requirements Courtesy: High performance network lab., Bristol

Evolution of Transmission Capacity

Spectral Efficiency (SE) Improvement Fixed 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 reach SE improvement is slowing down, meaning higher rate data need more spectrum Bit rate per channel (Gb/s) Relative optical reach with constant energy per bit Spectral efficiency (b/s/Hz) DP-QPSK DP-16QAM DP-64QAM DP-256QAM DP-1024QAM QPSK BPSK Gbaud Optical amplifier bandwidth (~ 5 THz) TDM WDM Multiplexing technology evolution PDM Multi-level mod.

Current Optical Networks :: Inflexible Super-wavelength Courtesy: High performance network lab., 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 Networking The term elastic refers to three key properties: The optical spectrum can be divided up flexibly Courtesy: Ori Gerstel, IEEE Comm. Mag. 2012

Elastic Transceivers The 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 channel spacing 250 km 400 Gb/s200 Gb/s400 Gb/s100 Gb/s 1,000 km Fixed format, grid Adaptive modulation QPSK 200 Gb/s QPSK16QAM 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 channelsDrop channels Optical splitter Wavelength selective switch

Multi-Granular Optical Switching FXC: Fiber switch BXC: Waveband switch WXC: Wavelength switch BTF: Band to Fiber Add channelsDrop channels

Architecture on Demand (AoD) Optical backplane cross-connections for AoD OXCs MEMS switch is used to interconnected all the Input-output ports and switching devices Courtesy: High performance network lab., Bristol

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

Flexible OXC Configuration Backplane implemented with 96x96 3D-MEMS Flexibility to implement and test several switch architectures on-the-fly Switching time 20ms Courtesy: High performance network lab., 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 standard WDM

Planning Elastic/Flexgrid Networks Input: Network topology, traffic matrix, physical layer models Output: 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 23

Examples RMLSA RSA Courtesy: Ori Gerstel, IEEE Comm. Mag. 2012

Cost-Efficient Elastic Networks Planning Using AoD Nodes Conventional ROADMsAoD ROADMs