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System engineering of alien wavelengths over the SURFnet network

System engineering of alien wavelengths over the SURFnet network Roeland Nuijts, SURFnet, roeland.nuijts@surfnet.nl Customer Empowered Fiber Networks Workshop, Prague, Czech Republic, September 13th-14th, 2010. Outline. Introduction Alien wavelength concept, advantages and disadvantages

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System engineering of alien wavelengths over the SURFnet network

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  1. System engineering of alien wavelengths over the SURFnet network Roeland Nuijts, SURFnet, roeland.nuijts@surfnet.nl Customer Empowered Fiber Networks Workshop, Prague, Czech Republic, September 13th-14th, 2010

  2. Outline • Introduction • Alien wavelength concept, advantages and disadvantages • Alien wavelengths in the SURFnet NGE (Next-Generation Ethernet) project • Alien wavelength for metro-connections using small form factor 10Gb/s DWDM interfaces on the existing SURFnet network • Alien wavelength for 40Gb/s long-distance SURFnet CBF connections • mix 40Gb/s PM-QPSK and 10Gb/s NRZ-OOK on standard SMF (G.652) with dispersion compensation • Conclusions

  3. Alien wavelength concept Rx Tx Tx Rx (a) conventional closed DWDM system Rx Rx Tx Tx Tx Tx Rx Rx (b) multi-domain DWDM systems Rx Tx Tx Rx (c) multi-domain DWDM systems with alien wavelength

  4. Alien wavelength advantages • direct connection of customer equipment  cost savings • avoid OEO regeneration  power savings • faster time to service  time savings • support of different modulation formats  extend network lifetime

  5. Alien wavelength challenges • complex end-to-end optical path engineering in terms of linear (i.e. OSNR, dispersion) and non-linear (FWM, SPM, XPM, Raman) transmission effects for different modulation formats • complicated system integration/functional testing • end-to-end monitoring, fault isolation and resolution • end-to-end service activation

  6. Application of alien wavelengths in the SURFnet NGE (Next-Generation Ethernet) project • Huge growth in data-oriented services over the past years • Push for low-cost, flexible, hence, ethernet connections • Until now Ethernet was transported over SDH/SONET infrastructure as a means to re-use existing infrastructure • With demand for more capacity and longer and high-capacity connections (WAN instead of LAN) there is now need for Carrier Ethernet • SURFnet NGE (Next-Generation Ethernet) project • SURFnet NGE project re-uses the existing DWDM layer

  7. SURFnet DWDM network - after Photonic Evolution project 1Q11 • All implemented ROADMs are of type 1x5 WSSes • Convert remaining fixed OADM nodes to ROADMs expensive maybe no time next year • Zwolle, Enschede, Nijmegen, Wageningen, Delft, Utrecht ready as of September 10th, 2010 • To be done: Asd1&2, remove fixed OADM in Ehv • Enables: • All-optical connection between TUD, TUE and TU (three Universities of Technology) • All-optical connection between Aachen (antenna field in Julich and Astron/JIVE in Dwingeloo) • All-optical pass-through between Amsterdam locations to close optical DWDM rings

  8. Alien wavelengths in the metro areaDWDM Architecture SURFnet6/7

  9. CIENA OME6500 and CPL 10Gb/s WDM transmitter and receiver DSCM (dispersion Compensation) CPL OME6500 CMD GMD

  10. Form factor improvement – 300pin to XFPTunable 50GHz channel spacing 10Gb/s DWDM transponder 300pin MSA transponder Typical power consumption 10W Footprint: ±100cm2 XFP transponder Typical power consumption 3W Footprint: ±14cm2

  11. Example: optical specifications of JDSU XFP Initial XFP exhibits negative chirp!

  12. Transient chirp g (ps) λ (nm) D (ps/nm km) 0  A negative frequency excursion on the rising edge corresponds to a positive wavelength excursion which means group delay increases hence velocity decreases  The opposite occurs on the falling edge  Both result in pulse compression which counteracts pulse broadening by dispersion, hence more reach (or dispersion tolerance)  Two methods to get negative chirp, unbalanced drivers or z-cut Mach-Zehnder modulators 0 λ (nm)

  13. Transmission performance versus dispersion with negative chirp Optimum dispersion around +800ps/nm • In each DWDM ring there are paths from each OADM node to Amsterdam1 and Amsterdam2, tailored to +800ps/nm as close as possible. Consequently, paths between rings can have up to +1600ps/nm dispersion and paths between OADM nodes less dispersion. Sufficient system performance for these dispersion values needs to be verified before deciding to use low-cost 10Gb/s interfaces in the photonic layer for NGE • Optimum dispersion can not always be achieved in systems due to 2 reasons: • in systems due to “quantization error” of DCF spools (i.e. DCF10, 20, ….) • wavelength dependence of dispersion in transmission and compensating fibers

  14. Calculate 10Gb/s wavelengths for NGE* Network diagram LP+IP traffic 24 23 1 21 7 22 6 19 5 3 2 + 18 17 8 13 16 9 12 10 11 14 Solved for required 10Gb/s wavelength connections and with minimum number of interfaces * Joint effort with Anteneh Beshir at the TUD (Delft Technical University)

  15. Required 10Gb/s wavelengths for SURFnet NGE - only LightPath traffic 230 10Gb/s interfaces required 82 different wavelength paths required  simulated optical transmission performance of all 82 wavelengths in order to verify whether these work and to check whether the first assessment of the FOM was correct

  16. Simulation results of transmission performance- dispersion, received power and OSNR OSNR Calculated OSNR was well above ROSNR (Required OSNR) for each of the 82 paths Measured OSNR of each 10Gb/s wavelength in the SURFnet network was well above the ROSNR Required performance can be delivered by the new low-cost 10Gb/s interfaces!

  17. Alien 40Gb/s wavelength transmission on SURFnet CBF connections JOINT SURFnet/NORDUnet 40Gb/s PM-QPSK alien wavelength DEMONSTRATION 10G 40G Copenhagen W S S End-to-end FoM = 1400 (a couple of dB margin over BOL OSNR limit - set against nonlinearities and potentially adverse effect from filter concatenation [4]) 416km TWRS Alcatel-Lucent (with dispersion compensation) 640km TWRS Nortel (without dispersion compensation) W S S Hamburg 40G 40G 10G 40G alien wave 900GHz 40G 350GHz W S S W S S Amsterdam Hamburg 5x10Gb/s @ 100GHz 10G 10G 5x10Gb/s @ 50GHz

  18. Alien 40gb/s wavelength on 10Gb/s-5x100km DWDM system using standard G.652 fiber and DCFs 34% pre-compensation 95% mid-span compensation 60% post-compensation 10G 10G 10x10Gb/s NRZ-OOK 40G 40G 10G W S S 1x40Gb/s PM-QPSK W S S 10G 10x10Gb/s NRZ-OOK 5x100km SMF 40Gb/s PM-QPSK 10 10 1 1 • Fairly unfavorable dispersion map due to zero-dispersion crossing at every span and hence high XPM efficiency 50GHz 50GHz  0 channels guard band

  19. Simulation results 40Gb/s alien wavelength 40Gb/s PM-QPSK P 10 10 1 50GHz 50GHz  0 channels guard band • The ROSNR of the 40Gb/s alien wavelength increases With increasing power level of the 10Gb/s NRZ-OOK channels, starting at about 4P, probably due to XPM • Increasing the power per channels of the 40Gb/s alien wavelength in the range where we conducted these simulations does not seem to affect (improve) the ROSNR so SPM (Self-Phase Modulation) does not affect the 40Gb/s alien wavelength • Best performance when 40Gb/s channel is stronger than 10Gb/s channels

  20. Conclusions • We have investigated using low-cost 10Gb/s DWDM interfaces for the SURFnet NGE project by using a heuristic model to determine the required wavelength topology and a transmission propagation model to determine the required performance • Simulation results show that new low-cost 10Gb/s XFPs deliver sufficient performance to be used for the NGE project and these results suggest they can be connected to the existing SURFnet DWDM layer • Preliminary simulation results of 40Gb/s PM-QPSK transmission on a DWDM system with standard (i.e. G.652 SMF) and DCFs and equipped with 10Gb/s DWDM signals show that power of the 10Gb/s channels should be well below the power of the 40Gb/s channel in order to avoid XPM

  21. Acknowledgements Some of the research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement nº 238875 (GÉANT)

  22. Thanks for your attention!Questions?roeland.nuijts@surfnet.nl+31-30-2305 305

  23. What limits system performance?ASE (Amplified Spontaneous Emission) Amplifiers are used to overcome fiber losses. Optical Noise is added by each amplifier. Engineering rules usually defined for equal spans (e.g. 20 x 20dB) which is not the case in the real fiber networks r(l) = 2 h n n sp (G(l) – 1) Slide courtesy of Kim Roberts, Nortel

  24. ƒ OA OA OA OA OA OSNR (Optical Signal-to-Noise Ratio) - Simple formula repeater SMF SMF SMF DCF DCF Tx Rx NF2 NF3 NFN-1 NFN NF1 Pin,1 Pin,2 Pin,3 Pin,N-1 Pin,N OSNR • Simple formula, accurate to within a few tenths of a dB but sensitive information needs to be provided to fiber suppliers, which equipment vendors don’t like: • NF of amplifiers • launch power per channel • minimum required OSNR => need simplification

  25. In order to quantify optical link grade, we propose a new method of representing system quality: the FOM (Figure of Merit) for concatenated fiber spans New method to quantify fiber link quality, FoM (Figure of Merit) Lj, span losses in dB N, number of spans A 120km 80km 120km 80km 120km 80km Total 600km B 80km 80km 80km 120km 120km 120km C 100km 100km 100km 100km 100km 100km 25

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