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Lecture: 9 Elastic Optical Networks Ajmal Muhammad, Robert Forchheimer Information Coding Group ISY Department
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Outline Motivation Elastic Optical Networking Flexible spectrum grid, tunable transceiver, flexible OXC Flexible Optical Nodes Routing and Spectrum Assignment Problem
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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
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High-speed data 400G, 1Tb/s Media Applications with Diverse Requirements Courtesy: High performance network lab., Bristol
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Evolution of Transmission Capacity
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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 0.01 0.1 1 0100200300400500 0.01 0.1 10 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 600 @25 Gbaud Optical amplifier bandwidth (~ 5 THz) TDM WDM Multiplexing technology evolution PDM Multi-level mod.
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Current Optical Networks :: Inflexible Super-wavelength Courtesy: High performance network lab., Bristol
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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
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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
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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
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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)
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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
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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
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Outline Motivation Elastic Optical Networking Flexible spectrum grid, tunable transceiver, flexible OXC Flexible Optical Nodes Routing and Spectrum Assignment Problem
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Common Building Blocks for Flexible OXCs
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Reconfigurable Optical Add-Drop Multiplexer (ROADM) Add channelsDrop channels Optical splitter Wavelength selective switch
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Multi-Granular Optical Switching FXC: Fiber switch BXC: Waveband switch WXC: Wavelength switch BTF: Band to Fiber Add channelsDrop channels
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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
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AoD Node Aimed to develop an optical node that can adapt its architecture according to the traffic profile and support elastic allocation of resources
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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
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Outline Motivation Elastic Optical Networking Flexible spectrum grid, tunable transceiver, flexible OXC Flexible Optical Nodes Routing and Spectrum Assignment Problem
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Routing and Spectrum Assignment (RSA) Spectrum variable (non-constant) connections, in contrast to standard WDM
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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
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Examples RMLSA RSA Courtesy: Ori Gerstel, IEEE Comm. Mag. 2012
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Cost-Efficient Elastic Networks Planning Using AoD Nodes Conventional ROADMsAoD ROADMs
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