Fresi, Francesco

Imran, Muhammad

Mastropaolo, A.

Meloni, Gianluca

Potí, Luca

Rommel, Simon

The scope, aims, and contributions of the COFFEE project for spectral efficiency enhancement and marketexposure are presented. <br/

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 18, 2017COFFEE - Coherent Optical System Field Trial for Spectral Efficiency EnhancementImran, Muhammad; Fresi, Francesco; Rommel, Simon; Mastropaolo, A.; Meloni, Gianluca ; Potí, LucaPublished in:CONNECT MagazinPublication date:2016Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Imran, M., Fresi, F., Rommel, S., Mastropaolo, A., Meloni, G., & Potí, L. (2016). COFFEE - Coherent OpticalSystem Field Trial for Spectral Efficiency Enhancement. CONNECT Magazin, (18), 22-23.COFFEE – COHERENT OPTICAL SYSTEM FIELD-TRIAL FOR SPECTRAL EFFICIENCY ENHANCEMENTAbstract—The scope, aims, and contributions of the COFFEEproject for spectral efficiency enhancement and marketexposure are presented.  Index Terms—Time Frequency Packing, Nonlinearitymitigation, multi-user receiver.I. PRESENTING COFFEEEvery telecom bandwidth provider would like to maximize its investmentin already installed optical fibre links before replacing them with new typesof fibres or overlaying another link. Spectral efficiency (b/s/Hz)characterizes the optimum utilization of spectral resources and definesoverall transmission capacity of a link. The COFFEE project aims atdemonstrating, through field trial experiments, the coherent optical datatransmission of a single superchannel at the high capacity of 1Tbps usinga reduced bandwidth (<200 GHz) over long-haul testbed routes. In orderto fulfil such requirements, innovative techniques, already developed inlaboratory, is being introduced in a field trial environment. Time-Frequency Packing (TFP) is used to increase the spectral efficiency [1].With respect to other commonly used techniques like orthogonalfrequency division multiplexing (OFDM) and M-ary quadrature amplitudemodulation format (M-QAM), TFP can guarantee for lower transceivercomplexity and bandwidth requirements, higher tolerance with respect tofibre propagation nonlinearities, reduced power consumption, and largerflexibility. Channel shortening (CS) [2], enhanced split step Fourier Method(ESSFM) [3], and multi-user processing are key enabling techniques [4]for these features. The implementation of such advanced techniquesrepresents a strong innovation in the area of telecommunications, and theuse of GÉANT infrastructures also pushes the relevance of the COFFEEobjectives toward market visibility. GÉANT installed link between Milanand Finkenstein shown in Fig. 1 is being used to evaluate the 1Tbpstransceiver prototypes in a real network infrastructure.II. UNDERSTANDING SPECTRALEFFICIENCY AND INFORMATIONCAPACITYMost of currently installed transmission links in core networks carry10Gbps OOK channels on the ITU-T fixed grid occupying 50GHz or100GHz of spectrum. In the past few years 40Gbps and 100Gbpschannels have also been installed to increase the overall link capacity. Toensure the optimum utilization of spectrum the ITU-T G.694.1 flex-gridstandard [5] has been defined allowing 12.5GHz spectral slices. Figure 2shows different data rate channels along with their spectral occupancies.Table I shows how optimized use of spectral resources increases theoverall link capacity for different channels.OPEN CALL – NETWORK ARCHITECTURE AND OPTICAL PROJECTSM. Imran , F. Fresi, S. Rommel, A. Mastropaolo High Capacity Optical Communications GroupSSSUP/CNITPisa, Italy m.imran@sssup.itGianluca Meloni, Luca Poti High Capacity Optical Communications GroupCNITPisa, Italy Luca.poti@cnit.it Figure 1: Milan-Finkenstein 675Km link for Tbps field trialFigure 2: Different data rate channels and spectral occupancy.Each column represents a 12.5GHz flex-grid slice.22      CONNECT ISSUE 18 2015III. LINK DESCRIPTIONThe fibre optic link chosen for the field trial connects Milan, Italy andFinkenstein, Austria over a length of 675km. The link consists of tenspans of ITU-T G.655 fibre with lengths between 45 and 80km, withamplification provided by Erbuim Doped Fibre amplifiers (EDFAs) asshown in Fig 1. The installed fibre is Corning LEAF on all spans, with ashort length of 13km of G.652 Corning fibre. Alcatel 1626LM DWDMequipment is installed in all the nodes.IV. NETWORK EMULATION IN LABThree nodes of Alcatel LM1626 equipment were installed and re-commissioned in the CNIT lab to characterize each component of a nodeand to emulate the network conditions before making the actual field trial.The network emulation helped to understand the compatibility issueswith 1Tbps transceiver and node component parameters such as thegain of amplifiers were optimized. Moreover, the amplifier loop backconfiguration at Finkenstein was also ascertained after evaluating different possible configurations. V. ENHANCING THE SPECTRALEFFICIENCY- KEY COFFEECONTRIBUTIONSThe overall transmission capacity of a link can be increased bytransmitting more bits per second per Hz of spectrum. But as we placechannels closer to each other we increase the inter-channel interference(ICI) degrading transmission performance. TFP employs severalinnovative techniques to mitigate ICI and other linear and non-linearimpairments and thus allows reduction of the spacing between differentchannels. Figure 3 shows three 160Gbps PM-QPSK channels packedtogether in 63GHz bandwidth using TFP. Table II shows achievedtransmission distance for different spectral bandwidths of a 1Tbpssuperchannel consisting of 8 sub-channels.OPEN CALL – NETWORK ARCHITECTURE AND OPTICAL PROJECTSIn the COFFEE project, a discrete time model of the transmission channelhas been derived to evaluate propagation over the link throughsimulations using a numerical tool built in CNIT. Both linear and nonlinearchannel models have been implemented. The key techniquesincorporated in TFP in the scope of the COFFEE project include:• Channel Shortening [2].• Nonlinear Impairment Mitigation [3].• Multiuser processing at the receiver [4].The system performance both in a single user and multi-user scenariohas been tested and optimised by emulating the Milan–Finkenstein fibreoptic link with a re-circulating loop in the lab. Use of multi-userprocessing will reduce the penalty due to ICI, and thus will enable a moretight binding of optical sub-channels.VI. FUTURE PLANSBased on system optimizations achieved in the lab, a field trial is nowunder way. As a fundamental outcome within the GN3plus communitythe COFFEE project allows to build expertise in innovative transmissiontechniques for next generation optical networks.ACKNOWLEDGMENTThis work has been carried out within the scope of the GN3plus projectCOFFEE as part of the GÉANT Open Call Programme.REFERENCES[1] G. Colavolpe et al., J. Lightwave Tech., vol. 27, n. 13, pp. 2357-2369, July 2009.[2] D. D. Falconer et al., Bell System Tech. J., vol. 52, pp. 1541–1562, Nov. 1973.[3 Secondini, Marco; Marsella, Domenico; Forestieri, Enrico, "Enhanced split-step Fourier method for digital back propagation," Optical Communication (ECOC), 2014 European Conference on , vol., no., pp.1,3, 21-25 Sept. 2014.[4] Colavolpe, G.; Fertonani, D.; Piemontese, A., "SISO Detection Over Linear Channels With Linear Complexity in the Number of Interferers," Selected Topics in Signal Processing, IEEE Journal of , vol.5, no.8, pp.1475,1485, Dec. 2011.[5] http://www.itu.int/rec/T-REC-G.694.1/en.Figure 3: Three adjacent PM-QPSK channels in 63GHz using TFPTABLE I. Different data rates and total C-band capacityTABLE II. Achieved Transmission distances for different spectralbandwidths for 1Tbps PM-QPSK superchannel23For more information on GÉANT Open Call seewww.geant.net/opencall

COFFEE - Coherent Optical System Field Trial for Spectral Efficiency Enhancement

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COFFEE - Coherent Optical System Field Trial for Spectral Efficiency Enhancement

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