Carlsson, Birger

Chi, Nan

Holm-Nielsen, Pablo Villanueva

Jeppesen, Palle

Peucheret, Christophe

The transmission characteristics of a two-level optically labeled signal with ASK/DPSK modulation are investigated under varying dispersion management. A limitation of extinction ratio and the resilience of fiber span, compensation ratio, and power level are obtaine

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Downloaded from orbit.dtu.dk on: Dec 17, 2017Dispersion management for two-level optically labeled signals in IP-over-WDMnetworks 4Chi, Nan; Carlsson, Birger; Holm-Nielsen, Pablo Villanueva; Peucheret, Christophe; Jeppesen, PallePublished in:Proc. of ECOC 2002Link to article, DOI:10.1109/ECOC.2002.204490Publication date:2002Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Chi, N., Carlsson, B., Holm-Nielsen, P. V., Peucheret, C., & Jeppesen, P. (2002). Dispersion management fortwo-level optically labeled signals in IP-over-WDM networks 4. In Proc. of ECOC 2002 (Vol. 2, pp. 1-2).Denmark: IEEE. DOI: 10.1109/ECOC.2002.204490Optical Labeling 5.5.1Dispersion management for two-level optically labeled signals inIP-over-WDM networksNan Chi, Birger Carlsson, Pablo V. Holm-Nielsen, Christophe Peucheret, Palle JeppesenCOM Center, Technical University of Denmark, Building 345V, Lyngby DK-2800, DenmarkTel:+45 4525 3782, Fax:+45 4593 6581, E-mail: nc@com.dtu.dkAbstract: The transmission characteristics of a two-level optically labeled signal with ASK/DPSK modulation areinvestigated under varying dispersion management. A limitation of extinction ratio and the resilience of fiber span,compensation ratio, and power level are obtained.IntroductionRapid converging of telecommunicaiton and datacommunication networking drive the future ultra-highspeed data-centric network evolving into an IPnetworking on a WDM physical infrastructure [1]. Withrespect to efficiency and cost effectiveness, newswitching technologies are required to merge theintermediate layer such as ATM and SDH and to routeindividual packets without converting the packet fromoptical to electrical format. Although the opticalwavelength can serve as an optical label in MP (Sscheme, a second level of optical label is stillnecessary for provisioning, maintaining, and restoringswitched light-paths. This second level optical labelcan be approached by a sub-carrier modulation [2] orby an orthogonal modulation format [3] combiningASK and DPSK modulation in a single carrier.In this paper, two-level optically labeled signals withorthogonal ASK/DPSK modulation are modeled andthe transmission characteristics under differentdispersion map, span length, degree of compensationand input power level are investigated for the first time.The maximum value of extinction ratio of the payloadis found at 9.53dB. Very low eye opening penalty(EOP) and considerable resilience of input power levelup to 25dB are demonstrated in the pre- and hybridcompensation scheme.PrincipleThe orthogonal ASK/DPSK modulation format provesthe possibility of deploying two-level optical labeling.The wavelength of the ASK modulated packet servesas its own first level label, and the second level label isachieved by modulating the label informationorthogonal to the packet data, i.e., by modulating thephase of the optical carrier. In the network nodes, thewavelength and/or the orthogonal modulated label areused for routing the packets, and can be swapped.In our system an intensity modulated payload at 10Gbitls accompanied by a DPSK modulated label at 2.5Gbitls is considered. The ASK and DPSK modulationare realized by a Mach-Zehnder modulator and aphase modulator, respectively. A 1-bit delay Mach-Zehnder interferometer is used for the DPSKdemodulator. The system setup of two-level opticallylabeled signal transmission is shown in Fig.1.IP NPavoad HeaderFig.1 Transmission setup of two-level optical labelingsystem.In order to detect the DPSK label, a limited extinctionratio is required, which is unlike a traditional intensitymodulation optical communication system, where highextinction ratio is preferred. An ASK/DPSK modulatedsignal with finite extinction ratio can be expressed inEquation (1), Where the mark 'p' is for the payload and'r is for the label, respectively, q the data sequence, Tthe period, g the pulse shape. The extinction ofpayload is lOlog(i), Suppose the pulse shape ofthe label is square, five distinguishing power levels areobtained at the output of the label demodulatordepending on different possibility of payload data andlabel data, as shown in Table 1.Table 1 Output power of label at different combinationof the pa load data and label data.Label Payload Output power oflabelql,. qp.4n, qp.4(nI _1)1, I gpQt)I I, 0and 0, I gp(t) H _______04 4 20,0 H0, 1 and 1, 0 gp(t) H 4gPT)0 4 4 21,land0,0 0(1)1S(t) * Hftl Pp4n I (4n m)Tp >expi £(1 qn)g(t nT.>.n P R I JAuthorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on March 17,2010 at 08:43:04 EDT from IEEE Xplore.  Restrictions apply. Optical Labeling 5.5.110404|_1i l°J l _02(a) I o4°oS XC i (b)o . 0-4 0 5 10 la 0 (c)Input powar(dBrn) Input power(dBrn)Fig.3 Contour plot of EOP for the payload as a function of Input power(a)post-compensation, (b) pre-compensation and (c) hybrid compensation.0.4-.3-02-0* 0410.02 3 4 5 a 7 N 0 10Extinction ratio of payload(dB)Fig.2 The output eye opening of label versusextinction ratio of payload, the inset figure shows themulti-level eye diagram of detected label.Then the eye opening of this eye diagram multi-levellabel can be derived from table 1, which has a simpleexpression as (5 HI)/4. The output eye opening oflabel as a function of extinction ratio of payload isshown in Fig.2. To obtain an open eye the extinctionratio of the payload must be no larger than 9.53dB.According to this limitation to extinction ratio inducedby the label as well as the requirement for gooddetection of the payload, we apply 6dB in the followinganalysis.Transmission performanceIdeally, the payload in ASK format is independent ofthe DPSK-modulated label, but in reality, there arecomplex interactions between the two orthogonalchannels during fiber transmission, which stems fromthe fact that the self phase modulation of the ASKpayload due to the fiber nonlinear effect give rise tophase noise on the label, and in turn, the phase noisecan be converted into the intensity fluctuation ofpayload through fiber dispersion. Therefore distincttransmission characteristics of the ASKIDPSKmodulated signal can be predicted and detaileddispersion and nonlinear effect must be included inthe simulation.We investigate varying fiber span consisting ofstandard single mode fiber (SMF) compensated bydispersion compensation fiber (DCF) at differentdegree. The EOP performance of the payload in thepost-, pre- and hybrid compensation schemedepending on SMF length, compensation ratio andinput power are demonstrated in Fig.3. Hybrid and10 4 0 5 1 1 5 20Input power(dBmr)and compensation ratio forpre-compensation show a good tolerance to powerlevel (up to 25dB) and compensation ratio when thenormalized EOP is below 5 dB. The optimumcompensation ratio in these three cases is found lessthan 100% and decreases when increasing the SMFlength. The lowest penalty of the payload is obtainedin the pre-compensation scheme. No distinct in thetransmission performance of the label is observed inall three cases. Fig.4 gives the EOP performance ofthe label in hybrid compensation scheme. It is alsofound that although the DCF can improve the eyeopening of the payload, the label will always bedegraded no maHter which com- pensation ratio isselected.1.0S 02E o0o0505303025Input power(dBm)Fig.4 Contour plot of EOP for the label depending oninput power and compensation ratio at hybridcompensation scheme.ConclusionWe have studied the transmission performance of thetwo-level optically labeled signal with an orthogonalASK/DPSK modulation format. The extinction ratiomust be less than 9.53dB to get an open eye of thedetected label. Hybrid and pre-compensation schemeshow a considerable power level resilience.AcknowledgementThis work is performed in the IST STOLAS (SwitchingTechnologies for Optically Labeled Signals) project.References1 N. Ghani, Optical Networks Magazine, Vol.1,No.2, pp.45-58, 2000.2 B. Meagher, et al, J. Lightwave Tech., Vol.18,No. 12, pp. 1978-1987,2000.3 T. Koonen, et al, Proc. ECOC'01, 2001.Authorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on March 17,2010 at 08:43:04 EDT from IEEE Xplore.  Restrictions apply. 

Dispersion management for two-level optically labeled signals in IP-over-WDM networks 4

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Dispersion management for two-level optically labeled signals in IP-over-WDM networks 4

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