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ROADM Network Elements Brandon Collings Optical Networks Research, JDSU [email protected] OFC 2007 OThR1 Overview Market Drivers for ROADM Networks Primary ROADM Network Features ROADM Node Building Blocks and Node Architectures Physical Layer Operational Features and Automation ROADM Component Characteristics and System Performance Network Management Current and Future Trends 2 © 2007 JDSU. All rights reserved. Market Drivers for ROADM Networks Bandwidth is increasing… Capacity increase is significant But the real story is how that capacity is evolving… source: G.K. Cambron, AT&T, OFC/NFOEC ‘06 4 © 2007 JDSU. All rights reserved. Drivers of the Today’s All Optical Networks Triple Play Services Rich Media Services US HQ Business Services Tokyo 5 © 2007 JDSU. All rights reserved. Consumer Driven Applications Content and bandwidth is evolving in a peer-to-peer topology Bandwidth is increasing and predictability decreasing Downloading TV programs from the Web is becoming more popular with consumers. There was a 39% increase in subscription rentals of TV content and a 255% increase in TV-title digital video downloads between August 2005 and August 2006. (NPD Group) In December 2006, Xbox Live surpassed 4 million members worldwide. Microsoft expects it to surpass 6 million members by the summer of 2007. According to YouTube, it is currently serving 100 million videos per day, with more than 65,000 videos being uploaded daily. In January of 2007 Apple announced that more than two billion songs, 50 million television episodes and over 1.3 million feature-length films have been purchased and downloaded from the iTunes Store 6 © 2007 JDSU. All rights reserved. Rich Media Services Have Changed the Network Model The “Telephony Network” 7 Sonet-SDH network Bandwidth predictable Traditional usage voice, dial-up Low bandwidth, low use and short duration © 2007 JDSU. All rights reserved. The Agile Optical Network DWDM Network High bandwidth applications Always-on Unpredictable traffic and growth patterns Market Overview : Technology Trends $900 Agile + Fixed CAGR = 19% $800 $700 39% $600 $(M) $500 $400 $300 Rapid Transition from Fixed to Agile 79% $200 $100 61% Agile CAGR = 55% 21% $2004 2005 2006 Agile 2007 2008 Fixed Source: Ovum-RHK, Transition to agile optical network drives ROADM and related modules growth, 2/2006 CAGR data is 2004-2010 8 © 2007 JDSU. All rights reserved. The Agile Optical Network is Happening Today “While not everyone has announced their deployment of Agile Optical Networks, most are using them in some form or fashion” Brett Azuma Exec VP, Ovum-RHK 9 © 2007 JDSU. All rights reserved. Primary ROADM Network Features Let’s just get this out of the way… Unsuccessful Business Case COST! Successful Business case in some market segments A Technology and Manufacturing Challenge 11 © 2007 JDSU. All rights reserved. Static Networks Based on Fixed-Wavelength Filters Topology and capacity/node determined at time of network design – Traffic projections based upon best estimates at the time – Frequently changes even during design/bid/deployment – Not always cost effective to “overbuild” the system Hub Can lead to premature system exhaust – Expected system lifetime: 5-10 yrs – Traffic projections not accurate leading to premature system exhaust Ch 1-8 Ch 1-32 • Insufficient l’s available to hot spots • Unlit l’s to cold spots cannot be utilized – Topology is inconsistent for emerging applications • Telephony, SAN, Enterprise, VoD, TBD topologies look different Ch 9-16 Physical WDM Ring 12 © 2007 JDSU. All rights reserved. Ch 17-24 Ch 25-32 ROADMs Enable Any-Node-to-Any-Node Topologies – Relieves need for accurate traffic growth forecasting (2x1 Switch+VOA) Array MUX TAPs & PD Arrays ROAM ROADM DEMUX Provision wavelengths independently between nodes No blocking extends system life to capacity limitation ADD CHANNELS VOA Tap PD DEMUX TAP & PD Array ROADM DROP CHANNELS Demux-T ROADM ROADM ROADM Physical WDM Ring 13 © 2007 JDSU. All rights reserved. All Optical Ring Interconnect Reduce OEO Costs ROADM ROADM ROADM ROADM OEO transition requires additional equipment with each wavelength Electrical switching fabrics generally not as scalable Traffic can be routed without craft visit to node ROADMs are bit-rate independent – 14 Removes cost of OEO and electrical fabric ROADM Nodes capable of remotely routing full capacity of channels without additional equipment – – Required O/E transponders on both rings Requires electrical switch and grooming fabric Multi-Degree ROADM Nodes enable inter-ring traffic to remain in the optical domain – ROADM Ring-to-Ring traffic previously electrically cross-connected – – ROADM OEO ROADM Implement higher line rates when, where and if the economics prove in © 2007 JDSU. All rights reserved. All Optical Ring Interconnect Reduce OEO Costs ROADM ROADM ROADM ROADM ROADM ROADM Ring-to-Ring traffic previously electrically cross-connected – – OEO transition requires additional equipment with each wavelength Electrical switching fabrics generally not as scalable Traffic can be routed without craft visit to node ROADMs are bit-rate independent – 15 Removes cost of OEO and electrical fabric ROADM Nodes capable of remotely routing full capacity of channels without additional equipment – – Required O/E transponders on both rings Requires electrical switch and grooming fabric Multi-Degree ROADM Nodes enable inter-ring traffic to remain in the optical domain – ROADM Implement higher line rates when, where and if the economics prove in © 2007 JDSU. All rights reserved. Accelerated Service Roll-out Remote provisioning and automated control plane enable more rapid service commissioning – – – – 16 Shorter Time-to-Revenue and Return on Investment Increased customer capture Shorter and predictable deployment intervals Network topology flexibility reduces network configuration churn © 2007 JDSU. All rights reserved. ROADM Node Building Blocks and Node Architectures Four Basic Types of ROADM Components Tunable Channel Filter Tunable Band Filter PLC ROADM 18 © 2007 JDSU. All rights reserved. Wave Blocker (WB) Wavelength Selectable Switch (WSS) Typical Tunable Channel Filter Node Architecture From West Coupler To East Coupler OA OA Wave Blocker Tx Tx Tx Tx Receivers Rx Rx Rx Rx Tunable Filters DROP ADD Transmitters Independent access to all wavelength channels – Number of Add/Drop ports less than maximum wavelength count Tx/Rx ports are wavelength provisionable (colorless) Supports drop and continue – Waveblocker required for wavelength reuse Add channels power equalized – Express channels equalized if WaveBlocker included 19 Supports 2-degree nodes © 2007 JDSU. All rights reserved. Typical Tunable Band Filter Node Architecture From West OA Band Filter DROP ADD Channels added/dropped in bands – Width of bands may be fixed or adjustable – Band is tunable in wavelength 20 Tx/Rx ports are wavelength specific (colored) Wavelengths may be reused Add channels power equalized Does not support drop and continue Supports 2-degree nodes © 2007 JDSU. All rights reserved. OA AWG Tx Tx Tx Tx Receivers Band Filter Rx Rx Rx Rx AWG To East Transmitters Typical WaveBlocker Node Architecture From West Coupler 21 AWG Tx Tx Tx Tx Wave Blocker OA Rx Rx Rx Rx AWG Coupler Block OA Receivers To East DROP ADD Transmitters Independent access to all wavelength channels Tx/Rx ports are wavelength specific (colored) Express and Add channels are power equalized Supports drop and continue Supports 2-degree nodes © 2007 JDSU. All rights reserved. Typical PLC ROADM Node Architecture From West Coupler OA To East PLC ROADM OA 22 DROP ADD Independent access to all wavelength channels Tx/Rx ports are wavelength specific (colored) High level of integration – – – – Tx Tx Tx Tx Receivers Rx Rx Rx Rx AWG Add direction wavelength multiplexing Per channel power monitoring (Add and Express) Add and Express channel power equalization Express or Add channel selection Supports 2-degree nodes © 2007 JDSU. All rights reserved. Transmitters PLC ROADM Block Diagram 220 mm X 135 mm X 36 mm : DOUBLE SLOT MS A PD 1 VPD 1 COMMON INPUT DROP OUTP UT SPLITTER COMMON OUTP UT DEMUX AWG MUX AWG VPD 2 PD 4 PD 5 EXPRESS OUTP UT EXPRESS INPUT PD 2 PD 3 LEGEND VOA ADD INPUTS SWITCH TAP DETECTOR PD: Physical VPD: Virtual 23 © 2007 JDSU. All rights reserved. Mux and Demux WSS Node Architecture To East Receivers WSS WSS Tx Tx Tx Tx OA Rx Rx Rx Rx From West DROP ADD OA Transmitters Independent access to all wavelength channels – Number of Add/Drop ports less than maximum wavelength count – Cascade secondary WSS components off primary WSS for additional ports 24 Tx/Rx ports are wavelength provisionable (colorless) Express, Add and Drop channels power equalized Does not support drop and continue Supports 2-degree nodes © 2007 JDSU. All rights reserved. Demux WSS Node Architecture From West To East Coupler OA OA WSS Tx Tx Tx Tx Receivers Rx Rx Rx Rx Coupler DROP ADD Transmitters Independent access to all wavelength channels – Number of Add/Drop ports less than maximum wavelength count – Cascade secondary WSS component off primary WSS for additional ports 25 Tx/Rx ports are wavelength provisionable (colorless) Express, Add and Drop channels power equalized Does not support drop and continue Supports 2-degree nodes © 2007 JDSU. All rights reserved. Multi-Degree WSS Node Architectures Demux 1xN WSS North In South In Mux Nx1WSS North Out South Out East In East Out West In West Out Demux WSS selectively routes wavelengths to destination Replace Mux Demux WSS WSS with with power power combiner splitter output degrees Mux Demux WSS WSS selectively selectively accepts routeswavelengths wavelengths Mux WSS selectively accepts wavelengths intended for its intended for its each respective respective degree degree respective degree – isolation for those wavelengths not intended for – Provides Blocks undesired wavelengths a given its respective degreedegree 26 © 2007 JDSU. All rights reserved. Multi-Degree Demux WSS Node Architecture Coupler Tx Tx Tx Tx ADD Coupler WSS DROP Rx Rx Rx Rx OA OA North East West Coupler OA OA WSS Coupler Tx Tx Tx Tx Coupler Rx Rx Rx Rx OA WSS ADD © 2007 JDSU. All rights reserved. OA OA 27 South DROP Rx Rx Rx Rx Rx Rx Rx Rx Coupler Coupler ADD Tx Tx Tx Tx ADD Tx Tx Tx Tx WSS Coupler DROP DROP OA Characteristics of Multi-Degree Demux WSS Architecture Supports any wavelength from any degree to any degree Drop port count limitations due to port sharing with interdegree connections Add/drop ports are colorless – No add port filtering rejects rogue wavelengths or noise Does not support drop and continue Drop and express channel equalization provided by WSS OA 28 © 2007 JDSU. All rights reserved. OA Rx Rx Rx Rx South DROP Coupler Coupler ADD Tx Tx Tx Tx WSS – Add port VOAs provide add channel equalization Multi-Degree Mux WSS Node Architecture Tx Tx Tx Tx ADD WSS AWG OA Coupler AWG DROP Rx Rx Rx Rx OA North East West WSS Coupler OA OA AWG Coupler Tx Tx Tx Tx OA Rx Rx WSS Rx Rx AWG ADD DROP AWG © 2007 JDSU. All rights reserved. South DROP AWG OA OA 29 Coupler WSS Rx Rx Rx Rx Rx Rx Rx Rx Tx Tx Tx Tx AWG ADD Tx Tx Tx Tx ADD AWG DROP OA Characteristics of Multi-Degree Mux WSS Architecture Supports any wavelength from any degree to any degree Add/drop ports present for all supported channels Add/drop ports are colored – Add port filtering rejects rogue wavelengths Supports drop and continue Add and express channel equalization provided by WSS OA 30 © 2007 JDSU. All rights reserved. Rx Rx Rx Rx South DROP Coupler WSS OA AWG ADD Tx Tx Tx Tx AWG – No per channel power control on drop ports (unless VOAs included) Multi-Degree Mux and Demux WSS Node Architecture ADD Tx Tx Tx Tx WSS Coupler WSS DROP Rx Rx Rx Rx OA OA North East West Coupler WSS OA OA Coupler Rx Rx Rx Rx OA Tx Tx Tx Tx WSS WSS ADD WSS © 2007 JDSU. All rights reserved. South DROP Coupler OA OA 31 Rx Rx Rx Rx Rx Rx Rx Rx WSS ADD Tx Tx Tx Tx ADD Tx Tx Tx Tx WSS DROP DROP OA Characteristics of Multi-Degree Mux and Demux WSS Architecture Supports any wavelength from any degree to any degree Drop port count limitations due to port sharing with interdegree connections Add/drop ports are colorless – Add port filtering rejects rogue wavelengths and noise Supports drop and continue Add and express channel equalization provided by Mux WSS © 2007 JDSU. All rights reserved. OA OA 32 Rx Rx Rx Rx South DROP Coupler WSS ADD Tx Tx Tx Tx WSS – Demux WSS provides drop channel power control Optical Layer Architectural Feature Comparison Tunable Filter Wave Blocker PLC WSS (Mux) WSS (DMx) East/West Node Equipment Separability Add/Drop with Channel Granularity O Access to Any Combination of Channels O Add/Drop Port Count Equal to Channel Count - O Non-service Affecting Upgrades O Drop and Continue - - Equalization of Expressed Channels - Add Channel Rogue Wavelength Protection - Add Channel Power Control O O Drop Channel Power Control - - - - Colorless ports O - - O Mesh Topology/Higher Degree Node Support - - - Feature Intrinsically Supported O Support depends upon particular configuration or inclusion of specific elements (i.e. VOA’s) - Not Supported 33 © 2007 JDSU. All rights reserved. Physical Layer Operational Features and Automation ROADM Network Operational Features and Automation Reconfigurability requires visibility into the optical layer and automated control – Monitor wavelength routing – Monitor optical layer performance – Provide feedback for channel power adaptation Automated optical layer eases installation and operational activities – – – – – – Quicker, cheaper, more predictable installation intervals Reduces required craft training and in the field measurements Minimizes complex activities such as power measurement and balancing Neighbor node and configuration discovery Minimizes errors Provides fault correlation Automated control enables increased performance and reliability – Longer system reach due to channel power equalization – Increased adjustment accuracy than possible manually – Performance monitoring and early warning alarms Simplifies support for alien wavelengths 35 © 2007 JDSU. All rights reserved. Optical Layer Monitoring Components Possible Monitored Parameters – – – – Optical channel power OSNR Wavelength alignment Wavelength ID or tag Characteristics – – – – – Measurement refresh rate Single or multi-input (shared) Single channel dynamic range Adjacent channel dynamic range Accuracy Two Basic Types Parallel Scanning AWG Scanning Tunable Filter 36 © 2007 JDSU. All rights reserved. Automatic Optical Power Management ROADM networks have a rich complement of power control actuators – Per channel power control at ROADMs – Total average gain control at EDFAs 37 © 2007 JDSU. All rights reserved. Automated Channel Power Equalization Channel power levels become unequal – – – – Accumulated optical amplifier gain shape Non-uniform fiber loss Inter-channel Raman pumping Optical elements Added channels require leveling when introduced into system – Many transponders do not produce tightly controlled output power – Power level may not be appropriate – Insertion loss of add path can vary Feedback algorithms control both optical amplifier and per channel attenuation – Optical amplifiers operate on all channels – Goal is to minimize amplifier gain – Minimizes OSNR degradation 38 © 2007 JDSU. All rights reserved. Channel Power Level Transient Timescales min/hour/day/year ~2ms ~100ms Long Term Effects Spectral Hole 15 Burning EDFA Transient sat sat Hole Depth (dB) GAIN (dB) •Fibertime loss aging l for Blue Curve•PDL •Upstream fiber break or power •Laser aging •Gain spectrum Difference of gain spectra failure changes due to 10 l for Redinput Curve •Rapid decrease in power change in channel Holes at l and/or channel count loading •EDFA reacts to maintain 1540 1560 5 1540 1560 stable gain for surviving •Change can be WAVELENGTH (nm) positive or negative channels sat Srivastava et al, OFC 1995 39 © 2007 JDSU. All rights reserved. Reaction Rate of Power Control Power Measurement (Optical Channel Monitor) – Parallel techniques: capable of sub-millisecond – Scanning techniques: 10’s of ms to seconds • Technology dependent – Multi-Input OCMs • Utilizes high isolation Nx1 selection switch • Decreases refresh rate by >N times Attenuation Change Actuation – VOAs: typically on the order of milliseconds – ROADMs: several milliseconds to seconds • Technology and magnitude of attenuation change dependent 40 © 2007 JDSU. All rights reserved. Power Level Transient Mitigation Transient suppression in the EDFA – ROADM and VOA reaction rates currently insufficient Gain change due to SHB requires ROADM attenuation correction – Gain change is typically small per amplifier (<0.5dB) – Change to channel power can accumulate with EDFA cascade – Depending upon ROADM attenuation speeds, some channels may be “unequalized” for several milliseconds During this period, system performance may be impacted – Duration is sufficient to trigger protection switch if impact is sufficiently severe – System design concern on extent to which system reach can be extended by capitalizing on channel power equalization 41 © 2007 JDSU. All rights reserved. Commissioning/Decommisioning Intentionally slow introduction and removal of optical power during network activities – Channel installation or removal – EDFA installation or removal – Fiber connection or disconnection Power control algorithms can react and keep system in equilibrium 42 © 2007 JDSU. All rights reserved. ROADM Component Characteristics and System Performance Cascading ROADM Nodes Details of the channel filtering become significant as number in cascade increases – Amplitude Response • Wide, flat top shape required – Phase response • a.k.a group delay which causes dispersion • Group delay ripple and structure must be minimized – PMD Channel spacing and Bit Rate – 10Gb/s typically not significantly impacted – 40Gb/s over 50GHz ROADMs has been deployed • Using advanced modulation techniques 44 © 2007 JDSU. All rights reserved. Typical WSS-based Node and Port Isolation …what happens to li in WSS? li,port_1 from deg 1 AWG AWG splitter Degree 2 splitter Degree 1 li,port_2 from deg 2 li,port_3 from deg 3 li,port_4 from deg 4 from deg m-1 li,port_m-1 li,add 1xm WSS AWG splitter Degree m-1 AWG 45 © 2007 JDSU. All rights reserved. from add port isolation (PIso) port selected to pass Output (at li) is coherent combination of li,port_2 along with m1 li signals, each suppressed by PIso OSNR Penalty versus Port Isolation Assumes nominal attenuation of 4 dB for channel power equalization N is the number of interfering signals present OSNR Penalty [dB, BER=1e-4] 3 2.5 N=8 N=16 2 N=24 N=48 1.5 N=64 1 0.5 0 35 37.5 40 42.5 45 WSS Port Isolation, PIso [dB] 46 © 2007 JDSU. All rights reserved. 47.5 50 Network Management Network Management Physical Layer Configuration Discovery – Inventory – Adjacent nodes – Intra-node element interconnection verification Wavelength Routing Verification Performance Monitoring – Full visibility into active wavelength performance – Threshold crossing warnings and alarms Alarm Correlation – Prioritize alarm closest to root cause – Suppress other alarms resulting from fault condition 48 © 2007 JDSU. All rights reserved. Current and Future Trends Current and Future General Trends Increased Component Integration – Reduce cost through circuit pack consolidation Increased Use of Open Photonic Layers – Improving physical layer automation increases acceptance criteria for non-native (alien) wavelengths – IP migration and proliferation of pluggable DWDM interfaces ROADMs Penetrating Edge/Access – Highly cost sensitive – Perhaps most rapidly evolving network space Enhanced In-situ Diagnostics – Link performance and engineering rules validation – Fiber plant characterization (dispersion, PMD, etc.) Increased utilization of topology flexibility and wavelength tunability – Restoration and disaster recovery – Load balancing – Protection switching 50 © 2007 JDSU. All rights reserved. Thank You
