Chi, Nan

Jeppesen, Palle

Oxenløwe, Leif Katsuo

Siahlo, Andrei

we demonstrate all-optical fiber signal processing at 10 Gbit/s, 40 Gbit/s and 80 Gbit/s including wavelength conversion, 2R regeneration and OTDM demultiplexing based on balanced nonlinear optical loop mirror and dispersion-imbalanced loop mirror

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Downloaded from orbit.dtu.dk on: Dec 17, 2017All-optical fiber signal processing based on balanced NOLM and imbalanced NOLMChi, Nan; Oxenløwe, Leif Katsuo; Siahlo, Andrei; Jeppesen, PallePublished in:28th European Conference on Optical Communication, 2002. ECOC 2002.Publication date:2002Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Chi, N., Oxenløwe, L. K., Siahlo, A., & Jeppesen, P. (2002). All-optical fiber signal processing based onbalanced NOLM and imbalanced NOLM. In 28th European Conference on Optical Communication, 2002. ECOC2002. (Vol. 3, pp. 1-2). Denmark: IEEE.Alo-optical Processing 6.3.5All-optical fiber signal processing based on balanced NOLM andimbalanced NOLMNan Chi, Leif Oxenlowe, Andrei Siahlo, 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: we demonstrate all-optical fiber signal processing at 10 Gbit/s, 40 Gbit/s and 80 Gbit/s includingwavelength conversion, 2R regeneration and OTDM demultiplexing based on balanced nonlinear optical loopmirror and dispersion-imbalanced loop mirror.IntroductionAll-optical signal processing as the critical function 'inrealizing all-optical network is of considerable interestbecause it makes conversion between the optical andelectronic domains superfluous. So far research hasmainly concentrated on the design of optical gatesthat use either the Kerr effect in optical fiber [1] orcarrier density related dynamics in semiconductoroptical amplifiers (SOAs) (2]. The operating speed ofSOA-based gates is limited due to the relaxation timeof the carriers. For the fiber-based gates, however.without carriers involved, the operating speed isdetermined by ultra fast fiber nonlinearity, whichprovides response times of only fs. Therefore all-fiber,all-optically controlled devices have great potential infuture ultrahigh-speed systems.In this paper we demonstrate for the first time all-fiber-based all-optical signal processing including'wavelength conversion, 2R regeneration and OTDMdemultiplexing in three balanced or imbalancednonlinear optical loop mirrors (NOLM), A new type of2R regenerator based on a high non-lineardispersion-imbalanced loop mirror (HN-DILM) isinvestigated and accomplished. After one or twosingle mode fiber (SMF) span transmission, thesignals at 10 Gbitls, 40 Gbitls and 80 Gbitls are re-generated by the 2R regenerator. The necessary fiberloop length is strongly reduced from 6 km to 1 km byapplying the highly non-linear DSF (HN-DSF) insteadof the conventional DSF, and a shorter fiber loopimproves stability and polarization insensitivity.PrincipleAn asymmetric NOLM can act as a saturableabsorber and strong filter in suppressing the amplifiedspontaneous emission (ASE) noise and reducing thetiming jitter and pulse-to-pulse interactions.Unibalancing of the NOLM can be achieved with anasymmetrically placed EDFA close to the loop coupler[31 or by making the dispersion of the fiber loopasymmetric [4] as so-called DILM. The imbalanceddispersion elemnents in the loop will vary the peakpower of the arms of the interferometer and thereforeresult in differential phase shift between the arms,The maximum transmission of the DILM occurs whenthe phase shift difference equals r.In our scheme the DILM operates in a working pointbeyond the peak of the transmission function shownin Fig.1(a), which means the pulse energies causegreater than , differential phase shift between thearms of the interferometer. Theoretical analysisshows that this scheme is stable against smallchanges in the input power [5]. Globally saturableabsorption provides an energy barrier to low-powercomponents and as a consequence the backgroundpedestal is rejected.The dependence of the loop transmission on the fiberlength of the non-linear segment is shown in Fig.1(b),when the input peak power is fixed at the workingpoint (0.3 W). To get an optimum transmission thenecessary length of DSF scheme is larger than 6 kmwhile the HN-DSF scheme is only 1 km. The relafivelyshorter fiber length of HN-DSP scheme will enhancethe system performance due to better stability andpolanrzation insensitivity.0.0- HN.0LFWfofkin pont ,DSF000~~~~~~~~~~~.0,0 02.4 O .6 2 4 6l3npLd ,¢ak PowerAYN} (b iber k;-fig1h (kff I)Fig,1 (a) Transmission function of the HN-DIL.M. (b)transmission characteristics of HN-DILM andconventional DILM as a function of the non-linearfiber length.ExperimentThe experimental set-up is shown in Fig.2. The signalsource Is a 10 GHz, 1557.3 nm erbium fiber ring laser(EFRL) that generates 4 ps full width half maximum(FWHM) pulses. After the modulator the pulse ismodulated by a pseudorandom bit sequence of 2 -1.Before transmission this data stream is passivelymultiplexed up to 40 Gbit/s and 80 GbitUs using a fiberinterleaver. The transmission fiber includes 50 kmconventional SMF and 8.6 km DOCF. A 10 GHz opticalsignal splitted from the EFRL is used as the pump fora wavelength converter made by a balanced NOLMconsisting 3 km DSF. The probe for the wavelengthconverter is provided by an external cavity tunablelaser at 1545 nm. The converted signal is then usedto open the switching window of the demultiplexingNOLM which is made of 2.5 km DSF.Authorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on March 10,2010 at 11:02:45 EST from IEEE Xplore.  Restrictions apply. All-optical Processing 6.3.5EFRL_Mt07_t 0 lM~~~M~~ jJ~~~40 40GWs "A,O40Gbits9 7 7 . ~~~~~~~~~~80GbiUs 7;iFig.2 Experimental setup. EFRL: erbium fiber ring laser, PC polarization controller, MZM: Mach-Zehndermodulator, TA: tunable attenuator, TL: tunable laser.The transmitted signals are then re-amplified and put regeneraffon is degraded by arbitrary polarizainto the HN-DILM to be reshaped. The HN-DILM, can be predicted that the improvement in rEconstructed from a 3dB coupler and 1030 m of SMF sensitvity would be larger if polarization mainand 1 km HN-DSF, acts as a nonlinear filter, fiber had been used in the loop.transmitting only the part of the pulse havingappropriate power and pulse duration. Due to the 1E *narrow pulse width, a consideration of peak power 1E 10 km W/i0s2IE-6 0~~~~~10G/i/i2R fgWWdaWand typical nonlinear coefficients indicates that a very * 400b/ftB2low dispersion fiber is needed to generate sufficient 1E4 50cm2R0 soob'sB2Bnonlinearity for switching. A measurement of the 1E-7 V 8 tkvMiftesimhighly nonlinear DSF shows very small dispersion ( - O1E40d2Rrcgcn-0.5 ps/nrnWm) at the operating wavelength and a 12-8high nonlinear coefficient of 10.6 W1krfV. When the 12E9signal is absent, the transmission of wideband ASE 1E.10 t_ _ _ _ _noise is shown In Fig.3. The polarizaUon controller is 4i5 .30 -25 .2Q -isused to bias the DILM to maximum reflection of in- RociOpowpr*(dBm)band noise. ,_ A-{,..--10-_ -20.5 30.g -40-a.-50-1s30 1540 1550 1560 1570Wavelength(nm)Fig.3 Transmission spectrum behaviour of the HN-DILM for wideband ASE noise and spectral output of40 GbitIs and 80 Gbitfs signals before transmission.The BER performance for back-to-back, transmissionand regeneration is shown in Fig.4. The receiversensitivity at 10 Gbitls is Improved from -31 dBm to -34 dBm by the 2R regenerator after 94 kmtransmission. The 40 Gbitls signal gets 0.5 dBimprovement due to the regeneration. The 80 Gbitls,however, has a relatively broad frequency bandwidthafter transmission, thus it Is difficult to get the wholebandwidth co-polarized simply by adjusting the bias ofthe polariation controller (see Fig.3); thetion. Itmceivertainingrig.,+ M5r- pU-iurnwoS TOr aum-Lu-Uaoun,transmission and regeneration at 10 Gbit/s, 40 Gbit/sand 80 Gbit/s.ConclusionWe have investigated and tested a 2R regenerator for10 Gbitts, 40 Gbit;s and 80 Gbitts signals based onan imbalanced NOLM with a novel configurationwhich has better stability and polarization insensitivity.All-optical all-NOLM-based signal processing up to 80Gbitls including wavelength conversion, OTDMdemultiplexing, and 2R regeneration is demonstratedafter one or two span of fiber transmission.ReferencesI S. Bigo, et al, IEEE J. Select. Topics QuantumElectron., Vol.3, No.5, pp.1208-1223, 1997.2 D. wolfson,et al, IEEE photon. Technol. Lett.,Vol.12, No.3, pp.332-334, 2000.3 B. Boscolo,et al, Eletron. Lett., Vol.37, No.2,pp.112-113, 2001.4 W. S. Wong, et al, Opt. Lett., Vol.22, No.15, pp.1150-1152, 1997.5 J. Smith, et al, J. Opt. Soc. Am. B, Vol.12, No.6,pp.1117-1125, 1995.-40Gbit/s "',---;80Gbtits "I \II a1_ . .i-;I,~~~~~~,. 8_11Authorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on March 10,2010 at 11:02:45 EST from IEEE Xplore.  Restrictions apply. 

All-optical fiber signal processing based on balanced NOLM and imbalanced NOLM

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All-optical fiber signal processing based on balanced NOLM and imbalanced NOLM

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