ICTON 2016 paper Tu.B3.3 Impact of Fiber Type and Raman Pumping in NyWDM Flexible-grid Elastic Optical Networks Arsalan Ahmad2, Andrea Bianco1, Hussein Chouman3, Guido Marchetto4, Sarosh Tahir4, Vittorio Curri1 1Dipartimento di Elettronica e Telecomunicazioni - Politecnico di Torino - Italy 2National University of Sciences and Technology, Islamabad, Pakistan 3 Télécom ParisTech , Université Paris-Sud, université paris saclay, Paris, France 4Dipartimento di Automatica e Informatica - Politecnico di Torino - Italy

Motivations Tranceivers based on multilevel modulation formats with coherent receivers No need for in-line compensation of chromatic dispersion Transparent wavelength routing possible in nodes Propagation impairment is a Gaussian disturbance enabling a simple closed-form for lightpath QoT IP traffic will grow at the average rate of 23% per year () Physical layer solutions – as Raman amplification – enhancing transmission quality must be tested and analyzed for network effectiveness () Cisco Visual Networking Index: Forecast and Methodology, 2015–2020

The GN-model and the OSNR as QoT of lightpaths outline The GN-model and the OSNR as QoT of lightpaths The LOGO strategy How to deal Hybrid Raman/EDFA amplification A transparent optical network as a weighted graph Network analysis heuristics Analysis of a Pan-EU network topology with flex-grid transmission Results presented as benefits of Raman amplification given as physical layer utilization

GN-model () : A simple and accurate equivalent model for fiber links with HFA …… Ls D, adB, Aeff EDFA Raman pump Transparency: GEDFA + GRA Lf Degradation of the QoT of available lightpaths given by the generalized OSNR in Rs NLI disturbance in Rs ASE noise in Rs () A. Carena et al. “Modeling of the impact of nonlinear propagation effects in uncompensated optical coherent transmission links,” JLT, vol. 30, no. 10, pp. 1524–1539, 2012

Hybrid Raman/EDFA fiber amplifiers (HFA) Ls z 1 No Raman GRA Raman MPR() Moderate Pumping Regime The larger Ppump The smaller PASE The larger PNLI The larger the saturation () V. Curri, A. Carena, “Merit of Raman Pumping in Uniform and Uncompensated Links Supporting NyWDM Transmission, “ JLT, vol. 34, no. 2, pp. 554-565, 2016

LOGO() startegy: local-optimized global-optimized We globally optimize the transmission performance locally minimizing the OSNR degradation in each fiber span Degradation of generalized OSNR in Rs Optimal power per channel () P. Poggiolini et al. “The LOGON Strategy for Low-Complexity Control Plane Implementation in New-Generation Flexible Networks”, OFC 2013

An all optical transparent network With the knoweledge of the network physical details We set the optimal power per channel and manage the network as a graph weighted by the inverse-OSNR (IOSNR) A E B D H C G I F Example: QoT for lightpath travelling from node A to node G through nodes C and E: where

Flex-grid and flex-format nyWDM fch1 fch2 fch3 fch4 fch5 f DSP RSG=RS,slot· Ns Modulation Format I/Q Modulator Laser Number of Spectral Slots Ns fch Bch=RSG=RS,slot· Ns RbG=RSG· BpS Rb=RSG/(1+OH/100) Data at Bit-rate Rb RS,slot =12.5 Gbaud OH = 25% Ns = 1  5 fch tunable on ½ RS,slot Modulation formats PM-BPSK : BpS = 2 PM-QPSK : BpS = 4 PM-16QAM: BpS = 8 PM-64QAM: BpS = 12 Btot = 4 THz  SLtot=320 Modulation Format Net Bit rate (Rb) Gbitps Ns=1 Ns=2 Ns=3 Ns=4 Ns=5 PM-BPSK 20 40 60 80 100 PM-QPSK 120 140 280 PM-16QAM 160 240 320 400 PM-64QAM 360 480 600

Which modulation format? PM-BPSK PM-QPSK PM-16QAM PM-64QAM Given the in-service BER BpS 2 4 8 12 Lightpath QoT OSNR in Rs [dB] 4 8 12 16 20 22 Given the origin node the destination node, and the route QoT as route OSNR

Elastic flexible-grid networks design We use a design procedure for elastic flexible-grid networks similar to the heuristic-based one used for fixed- grid Transmission-aware Logical Topology Design (LTD): Find the set of lightpaths but decide also which modulation format for each lightpath Routing and Spectrum Assignment (RSA) Route the lightpaths and assign portion of spectrum to each lightpath Spectrum is divided in 12.5 GHz slots, up to five contiguous slots can be assigned to a lightpath The RMLSA (Routing, Modulation Level and Spectrum Allocation) sub-problems are jointly solved The choice of the modulation format depends on the route QoT and sets the capacity per spectral slot Then the channel capacity can be enlarged occupying up to 5 slots, upon to spectral availability

Planning flexible-grid networks Input: Network topology, traffic matrix, physical layer models Proposed approach: describe Tx-Rx feasible configurations with (reach-rate-spectrum-guard band) tuples Output: RMSA (Routes, modulation format and spectrum allocation) Minimize utilized spectrum and/or number of transponders, and/or… Satisfy physical layer constraints Courtesy: E. Varvargios, OFC 2013

Network Design Heuristic Simple heuristic chosen because the focus of the work is to discuss the influence of physical layer parameters on network performance metrics, with no major emphasis on resource allocation policies Direct Lightpath Heuristic (DLH)() Each traffic demand is fulfilled by establishing a new dedicated lightpath beginning from the largest one Incorporation of detailed physical layer model ensures the a realistic adaptation of modulation format based on lightpath OSNR After selecting the modulation format, required spectrum slots are calculated and their availability if verified on the physical path In this work, we stop the analysis before reaching the traffic load that would imply request blocking () A. Ahmad et al. “Traffic Grooming and Energy Efficiency in Flexible-grid Networks”, IEEE ICC 2014

PAN-European network topology The analysis Three fiber types NZDSF SSMF PSCF Ls = 80 km  120 km HFA from 0% (EDFA) up to 60% Network traffic level: 500 Gbps  3000 Gbps Results presents as percentage of physical layer utilization, i.e., the spectral use : PAN-European network topology

SO vs. raman pumping Ls = 100 km - Traffic = 1000 or 1500 Gbitps RA0

SO vs. Span Length Traffic = 1000 Gbitps

SO vs. traffic Ls = 100 km

We showed that Raman pumping always helps network perfomances conclusions Transparent optical networks can be analyzed as a whole from the logical down to the physical layer thanks to a simple QoT parameter including ASE noise and propagation impairments We showed that Raman pumping always helps network perfomances Use of Raman pumping gives larger advantages in case of Low dispersion fiber: NZDSF Long span lengths High traffic

Questions… curri@polito.it

IGH with different traffic ordering policies We explore the impact that serving demands in different orders has on network performance. Six different orderings are defined using 2 parameters: The traffic capacity Ti,j and the physical length Di,j of the ligthpath: Traffic Based Ordering Ascending order of Ti,j (IT). Descending order of Ti,j (DT). Lightpath Physical Path Based Ordering Ascending order of Di,j (IL). Descending order of Di,j (DL). Hybrid Ordering: Extension of IT. The ordering of the traffic demands that have Ti,j = Cmax, which is done in ascending order of their Ti,j (IT-IL). Random Ordering (RAN)