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Towards Dynamic and Scalable Optical Networks

Discover the key requirements, technologies, and issues in achieving truly dynamic and scalable optical networks. Explore dynamic control planes, wavelength switching, higher data rates, and capacities, along with the challenges and possibilities of reaching 100Gbps. Learn about on-demand bandwidth capacity, lightpath control, and the integration with IP/MPLS for efficient traffic engineering. Find out about enabling technologies like electronic ROADMs and tunable lasers for dynamic networks of the future.

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Towards Dynamic and Scalable Optical Networks

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  1. Towards Dynamic and Scalable Optical Networks Brian Smith 3rd May 2005

  2. Towards Dynamic and Scalable Optical Networks • What is required to deliver truly dynamic optical networks ? • A Dynamic Control Plane • Technologies for Wavelength Switching • Considerations for achieving higher data rates + capacities. • Issues with 40Gbps • Is 100Gbps achievable ? • Getting maximum spectral efficiency in a dynamic optical network.

  3. A Dynamic Control Plane

  4. Lightpath Control • To deliver on-demand gigabit lightpaths, a fast and reliable distributed control plane is required • Reliable –transport infrastructure should remain stable during reconfigurations • Fast – otherwise its not on-demand ! • GMPLS is one control plane under development for optical networks by the industry. • Based on standard set of IP routing and signaling protocols • UCLP is an example of an R&E initiative (CANARIE) • TL1 interfaces controlled by a distributed service layer based on a web browser and network model.

  5. Evolving Towards Dynamic Lightpath Control • Features Required for Light-path Control • Topology discovery and link management. • Operator signaled light-paths (Network should automatically manage its own demand). • Client on-demand light-paths (High end users can individually control wavelengths). An important feature for future R&E networks ! • Integration with IP/MPLS control plane for dynamic traffic engineering e.g HOPI / DRAGON. • Dynamic protection – if required

  6. On-Demand Bandwidth Capacity Wavelength Switch Routers Backbone Network AccessNetwork Server Farm A B MeshNetwork User ControlledLightpath(e.g. for nightly databack-up) C High EndUsers D Available now between routers. Needs to evolve to support high data rates on wavelengths

  7. Example of need for on-demand wavelengths • 4 radio telescopes in an array – 12 hour observation • Assuming 1Gbps per telescope – 0.2 Petabits of data ! • How long would it take to back up the data to storage ? • With 100Mbps rate – ~23 days minimum assuming no packet loss. • With dedicated GigE wavelength – ~4 days. • If user can request an on demand 10GigE wavelength – ~5 hours. High-end Research users will require high capacity on demand services

  8. Enabling Technologies For Dynamic Networks

  9. Enabling Technologies for Dynamic Networks • Electronic ROADM • Optical ROADM • Tunable lasers • Tunable 10G DWDM XFPs will be available in 2006 • Integrated optical wavelength converter / tunable laser • Demonstrated in Labs using non-linear cross-talk in Semiconductor Optical Amplifiers – Capable of supporting up to 40Gbps

  10. Electronic ROADM DWDM DWDM WestFiber EastFiber NxN TransparentWavelengthSwitch(electrical) DWDM DWDM CWDM CWDM NorthFiber SouthFiber CWDM CWDM Trib 1310 Trib 1550 Trib 850 Trib 1310 • Native signal transparency with layer 1 performance monitoring • Simple Any-to-Any Multi-Degree grid interconnection • Simple to Engineer.

  11. Optical ROADM – Wave-blocker Wave-blocker Splitter Coupler Drop Filter Add Filter • Drop and Add Filters must be tuneable for maximum flexibility. • Hitless filter tuning is a problem. • Many discrete components so expensive • High insertion loss – Limits DCM – Limits reach between nodes for fully transparent networks.

  12. Optical ROADM – Wavelength Selective Switch (WSS) WavelengthSelective Switch Coupler OptionalExpansionPort DropChannels Add • Fewer discrete optical components • Fully flexible colourless add/drop • Lower insertion loss • Limited number of drop ports – Use expansion port !

  13. Comparison- Wavelength Switching

  14. Implementing ROADM Interfaces Pass-through Traffic NorthFiber SouthFiber OpticalROADMI/F OpticalROADMI/F DWDM DWDM DWDM DWDM DWDM DWDM NxN TransparentWavelengthSwitch(electrical) WestFiber EastFiber DWDM DWDM Trib 1310 Trib 850 Trib 1550 CWDM CWDM CWDMWest CWDMEast CWDM CWDM Trib 1310 Optical and Electronic ROADM complement each other.

  15. Multi-Degree ROADM Interfaces Optical Pass-through channels NorthFiber SouthFiber OpticalROADMI/F OpticalROADMI/F OpticalROADMI/F OpticalROADMI/F NorthWFiber SouthEFiber DWDM DWDM DWDM NxN TransparentWavelengthSwitch(electrical) DWDM DWDM DWDM WestFiber EastFiber DWDM DWDM First step towards full NxN photonic wavelength switch.

  16. Cost Comparison – 2.5G Traffic ~17

  17. Cost Comparison – 10G Traffic ~6

  18. Wavelength Switching - Cost sweet spots Note:For 2-degree metro ring applications. Also applies to 4-degree mesh architecture ChannelRate ElectronicROADM Optical ROADM 10G ElectronicROADM Optical ROADM 2.5G 4 8 12 16 20 24 28 32 Pass-through Channels

  19. The Future of 40G/100G

  20. 40Gbps/100Gbps • 40Gbps • 40Gbps DWDM trials and demonstrations becoming more common. • Ability to overlay on existing 2.5/10G links – a key driver ! • 40Gbps router interfaces have been demonstrated. • Dispersion must be controlled within ± 62 ps/nm. • PMD is an issue. Cannot exceed 2ps (outage < 3min/year) • 100Gbps • Can 100Gbps be achieved over DWDM ? • Dispersion tolerance even tighter - ± 25 ps/nm. • PMD more of an issue. Cannot exceed 1ps (outage < 3min/year)

  21. 40Gbps Dispersion Tolerance 6x80kmx26dB - 32 • 100GHz spacing SPM, XPM and FWM effects included Range of possible net dispersion Tunable Dispersion Compensation Required for 40Gbps.

  22. 100Gbps • Several published examples of single wavelength 100Gbps+ transmission. • Spectral width ~ 150 GHz for NRZ so won’t fit into a 100GHz spaced DWDM pass-band (~85GHz) ! • Dispersion limit for NRZ is ± 25ps/nm. • If we use non-binary coding – Spectral width reduced to 75GHz – Just fits within 100Ghz spaced DWDM band. • Needs tight control of laser + filter wavelengths. • Using >1 bit per symbol coding technique such as duo-binary or QPSK improves tolerance to dispersion and PMD. 100Gbps is achievable. Needs sophisticated coding!

  23. Polarization Mode Dispersion • Using 6x80kmx26dB with 6 EDFA and 6 DCM, the calculated average DGD (assuming fiber is post 1995) = 2.5 ps • The PMD tolerance (and expected outage) for various data rates is: Rate pmd tolerance system outages/yr 2.5G 30ps insignificant pmd outages/yr 10G 7.6ps insignificant pmd outages/yr 40G(NRZ) 2ps ~ 3 minutes/year assuming FEC 100G(NRZ) 0.9ps Requires PMD compensation

  24. How Much Capacity ?

  25. Summary • On-Demand Light-path Control Enabled by: • Distributed, Intelligent Light-path Control (UCLP, GMPLS) • Electronic and Optical ROADM. • Widely Tunable Laser Sources. • 40Gbps/100Gbps • 40Gbps can be deployed over existing 10G infrastructure with appropriate dispersion control + FEC. • 100Gbps will a challenge requiring sophisticated coding schemes and components for PMD mitigation.

  26. Thank You

  27. Impact of Tighter Channel Spacing • Four Wave Mixing (FWM) Increased FWM Impact – Reduced Reach.

  28. Impact of Tighter Channel Spacing • Cross Phase Modulation distortion (XPM) Increased XPM Impact – Reduced Reach.

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