Jeppesen, Palle

Le, Nghi Trong Quang

Peucheret, Christophe

Zhenbo, Xu

A transmission distance of 7500 km is numerically predicted for 160 Gb/s single channel fiber systems by using realistic dispersion parameters of ± 6 ps/nm/km. System tolerance on third order dispersion and optical filtering is investigated

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Downloaded from orbit.dtu.dk on: Dec 17, 2017Short period dispersion management of 160 Gb/s single channel fiber systemXu, Zhenbo; Peucheret, Christophe; Le, Nghi Trong Quang; Jeppesen, PallePublished in:Proc. of ECOC 2002Publication date:2002Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Zhenbo, X., Peucheret, C., Le, N. T. Q., & Jeppesen, P. (2002). Short period dispersion management of 160Gb/s single channel fiber system. In Proc. of ECOC 2002 (Vol. 3, pp. 1-2). Denmark: IEEE.Systems technologies P3.15Short Period Dispersion Management of 160 Gb/s Single Channel FiberSystemZhenbo Xu (1), Christophe Peucheret (1), Quang Le (1,2) and Palle Jeppesen (1)(1) COM, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark, xuz@com.dtu.dk(2) OFS Futel Denmark I/S, Priorparken 680, DK-2605 Brondby,, DenmarkAbstract A transmission distance of 7500 km is numerically predicted for 160 Gb/s single channel fiber systemsby using realistic dispersion parameters of ±6 ps/nm/fkm.filtering is investigated.IntroductiornThe idea of short period dispersion management(DM) basedi on short lengths of fibers whichalternatively have opposite dispersion sign isattracting increasing attention because of its powertulsoliton-like characters. In such a dispersion managedsystem. the average dispersion in each span is closeto zero and the input peak power is enlarged, whichboth reduces Gordon-Haus jitter effects and improvessignal to noDise ratio simultaneously. This enablessingle channel transmission at high bit rates at160 Gb/s and above. There is considerabletheoretical and experimental research going on at thatbit rate [1 -5]. Up to now, numerical simulations havepredicted about 8000 km transmission distance withdispersion parameters D= ±1 ps/nm/km [4], buit it isvery difficult to produce fibers with such a smalldispersion because of the small allowed tolerances inthe fiber geometry.In this work, we consider dispersion parameters of±6 ps/nm/km. Such values can be controlledrealistically in production. We predict a transmissiondistance of 7500 km neglecting polarization modedispersion (PMVD) and Raman effects. It is found thatsystem perormance is very sensitive to third orderdispersion (TOD) and that an optical filter cansignificantly reduce timing jitter due to pulse-to-pulseinteraction,System modelGaussian input pulses are used in a PRBS sequenceof length 210"1 transmitted at a wavelength of1550 nm. Each fiber span is 50 km long and its loss isfully compensated by an optical amplifier with a noisefigure of 4.5 dB. An in-line Gaussian optical bandpassfilter is inserted after each amplifier. We have foundby numerical simulation that the filter optimalbandwidth is 870 GHz. An electrical low-pass Besselfilter with a bandwidth of 0.7 times the bit rate is usedat the receiver. Anomalous dispersion fiber withdispersion of 6 ps/nm/km1 dispersion slope of0.03 pslnm /km, attenuation of 0.2 dB/km, effectivearea Aeft of 5Pm2 and normal dispersion fiber withcorresponding parameters equal to -6 ps/nm/km10.03ps/nm7lkm, 0.25 dB/km and 45 pm? are used.System tolerance on third order dispersion and opticalThe nonlinear index is the same for both fibers and istaken equal to 2.6x1020 mbW.The dispersion map in one amplifier span isdetermined by the map strength S which plays a keyrole in controlling the pulse breathing. S is given by,where LI and L2denote thelengthis and Xs and P,2 the group velocity dispersion(GVD) parameters of anomalous and normaldispersion fiber, respectively. TF HM is the full-widthhalf-maximum of the input pulse. We use the optimalvalue of S=1.6 [1] in our dispersion maps to avoid toostrong pulse breathing which can generate dispersivewaves that can destroy the balance of nonlinearityand dispersion. Fibers with opposite dispersion signsare placed alternatively in the amplifier span. Eachfiber length is about 235 m. The average dispersionI nL3 + 0)2!"] is chosen to be near zero. FiberLl + F-splicing loss inside the spans is neglected in ourinvestigation.Simulation resultsPahl em,RIhpersi,wups r}jr½Fig. 1 Maximum transmission distance for a BER oflxlY as a function of path average dispersion andpulse input peak powerIn Fig. 1 we show the maximum transmissiondistance which can be reached for a bit-error-ratebetter than 1 x109 for different path averagedispersions and initial pulse input peak powers. It canbe clearly seen thiat the optimum path averagedispersion is located in the anomalous range, wherethe system performance is much better than in theAuthorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on March 10,2010 at 07:46:39 EST from IEEE Xplore.  Restrictions apply. Systems technologies P3.15normal dispersion range. At J2aw = -0.005 ps2/km, weget the best result of 7500 km, where nonlinearitycounteracts dispersion perfectly, keeping pulseevolution regular and soliton-like.7000 _ _ .60001000-0.020 -0.015 -0.010 -0,005 0.000 0.005 t.0o 0,015 0,0200S,._,(ps /km)Fig. 2 Transmission distance as a function of theaverage third-order dispersion fi,. for differentvalues of the average dispersion parameter /32,.e.We have investigated the third order dispersiontolerance for system stability against changing fiberdispersion slope. Here I3o denotes the average thirdorder dispersion ,3 in one span. From Fig. 2 we findthat the transmission distance for 032u*=-0.005(ps2lkm) will be decreased to 6000 km (which is 85%of the maximum distance of 7000 km) when ,^varies in the ±0.004 (ps3/km) range. Outside thisrange the system is very sensitive to changes in Ba.and the transmission distance decreases rapidly.However, for P2,.= -0.01 (ps2/km), the range of P3aewith transmission reduced to 82%/o increases to±0.08(ps8lkm), and for Now, = -0.02 (ps2ekm), therange of u3,. increases to ±0.01(ps3/km) which givesvery stable transmission performance. Therefore, oursimulations show that the TOD tolerance range iswithin ±0.01 ps3/km and, as expected this rangeincreases with larger average dispersion. It can alsobe seen that for a given transmission distance, themaximum TOD tolerance depends on the optimumaverage dispersion.We have also studied the influence of having an in-line filter in each amplifier span, The results areshown in Fig. 3 where we present the calculated BERas a function of the number of spans in the followingcases: a) without noise and without filter, b) with noiseand with filter, c) without noise and with filter, in orderto assess whether the benefits were arising fromnoise filtering or from a reduction of pulse-to-pulseinteraction. Comparing eye diagrams a) and c), it isclear from Fig. 3 that without filter, timing jitterbecomes a serious problem even withoutaccumulated amplifier spontaneous emission (ASE).Fg. 3 Calculated BER as a function of the number ofspans with and without in-line filter.This means that pulse-to-pulse interaction is the mainlimiting factor that deteriorates such a dispersionmanaged system. An optimised filter with a bandwidthof 870 GHz can surprisingly improve the transmissiondistance by a factor of two. That is because phaseshifts between neighbouring pulses, which causepulses interaction by accumulation, can be destroyedby the filter. From eye diagram b) it can beunderstood that noise enlarges the timing jitter notonly by adding a random component to the signalspectrum but also by causing random fluctuations inphase change between neighbouring pulses. Ourresults show that a filter can greatly reduce pulse-to-pulse interactions and hence suppress the timing jittereffectively.ConclusionWe have shown by numerical simulations that shortperiod dispersion management is very promising forhigh speed long haul systems. A distance of 7500 kmwas obtained using alternating dispersion of±6 ps/nmlkm which is a realistic value from a fiberproduction point of view. Numerical results also showthat although the TOD tolerance is larger when theaverage dispersion is higher, for a given samedistance the maximum TOD tolerance range isdependent on the optimal average dispersion, whichis useful information for making experimental designs.We also find that an in-line optical filter is moreimportant for suppressing timing jitter due to pulse-to-pulse interaction than for reducing accumulated ASE.References1 T. Hirooka et al, IEEE Photon. Technol. Lett., Vol.12(2000), pp. 633-635.2 J. Martensson et al, OFC 2001, MF7.3 T. 1. Lakoba et al, J. Ughtwave Technol. Vol. 18(2000), pp. 1504-1512.4 L. J. Richardson et al, IEEE Photon Technol. Lett.,13 (2001), pp 209-21 1.5 A. H. LUang et al., Opt. Lett., Vol.24 (1999), pp 799-801.Authorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on March 10,2010 at 07:46:39 EST from IEEE Xplore.  Restrictions apply. 

Short period dispersion management of 160 Gb/s single channel fiber system

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Short period dispersion management of 160 Gb/s single channel fiber system

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