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/ OFC 200/ TUESDAY MORNINGdemonstrations of optical sampling of 160 Gbitls data signals were reported. Of special interest is signal monitoring using asynchronously sampled histograms which do not need a clock recovery process for monitoring and thus offer the possibility of bitrate transparency." Investigation of the histogram statistics enables estimation of the BER and identification of possible sources of signal degradation.)' 160 Gblt/s Reld trlal As an example, we report here a 160 Gbit/s RZ transmission experiment over field-installed fiber G.652" Fig 2. shows schematically the experimental setup. In the transmitter a mode-locked semiconductor laser was operated at 1550 nm with a repetition rate of I O GHz. The 10 GHz transform limited, 1.2 ps pulse train was intensity modulated with a pseudo random bit-aequence (PRBS 2' -1) using an external Mach-Zehnder type modulator. The 10 Gbit/s data signal was then multiplexed by a fiber delay line multiplexer (4 stages) to a 160 Gbitls single polarization RZ data signal. To ensure a multiplexed true PRBS data stream, the bit sequences were shifted against each other by (2'-I)/" bit periods with n = 2,4,8, 16. The 160 Gbitls RZ data signal was launchedwith 12 dBmintotheinstalledfiberlink of the Deutsche Telekom between the 3 cities in Germany as depicted in Fig. 2. The total length of thefiberlinkwas116kmSMF(dispersionD= 17 pslkm, loss including splices and connectors 32 dR, differential group delay about 2.2 ps). There was no in-line amplifier, but the fiber was backward Raman pumped (945 mW, gain 14 dB) at the output of the transmission line. The subsequent dispersion compensator comprised 21 km SC-DCF (0.5 dBlkm, D = -98 pslnmlkm, dBldh = 4 . 3 3 pslnm'lkm). Two different receivers were used. In the OTDM-experiment, the receiver comprised an optical demultiplexer for 160 Gbitls to 10 Gbitls demultipluring with subsequent electrical signal processing at 10 Gbitls. In the OTDMIETDM-experiment the receiver comprised an optical demultiplexet for 160 Gbitls to 40 Gbitlr demultiplexing with subsequent 40 Gbit/r to 10 Gbitlr electrical demultiplexing (ETDM receiver manufactured by Lucent Technologies in Nilrnberg, Germany). The optical demultiplexer used in both experiments was a UN1 with an SOA operating in the "gain-transparent" mode. The switching contrast of the device was about 23 dB for demdtiplexing to 10 Gbivr and 15 dB for demultiplexing to 40 Gbitk The width of the switching window was set to 5.2 ps in both experiments.We achieved error-free performance for all transmission experiments. However, a manual adjustment of the state of polarization at the fiber input was required to minimize degradation due to PMD. Despite significant daytime temperature changes during the experiments (environment: 10 to 2 5 T , l a b 20 to 3OoC), no readjustment of the dispersion compensation was needed. ConeluslonWe discussed optical signal processing for the next generation time division multiplexed (TDM) bit rate of 160 Gbitls. First field trials Show, that this technique has a...

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