ands) lumped Raman amplification in DCF manual polarization control, phase 50 GHz before and after the span diversity spacing Off-line electronic equalization and post-processing NRZ PMD 100 Gbit/s 155 (C+L 7200 km Ultra low loss fiber (a = 1.66 dB/km), mixed Coherent homodyne detection, phase bands) Raman and EDFA amplification, Raman and polarization diversity 50 GHz back-propagating pumps, span 90 km spacing NRZ PMD 100 Gbit/s 36 (C band) 401 km Unrepeated link Dispersion pre-compensation at the Remotely pumped Raman amplifier. Raman transmitter with DCF. Polarization pump 5.5W at the far end at 1276 and and phase diversity coherent transferred at 1430 through second order receiver. Electronic ISI equalization Raman. 30 dBm output EDFA booster NRZ PMD 171 Gbit/s 432 (C + 240 km 80 km long spans, mixed EDFA and Raman Digital coherent detection, 16-QAM Exte. L amplification with Raman back- homodyne with phase and bands) propagating pumps. Extended L band polarization diversity Next Generation Transmission Systems at the expense of a reduction in the receiver sensitivity, while PDM simply transmits two channels in parallel, each of which reduces the bandwidth only of a factor four but has also the sensitivity of a format with much less levels. A common factor for all the experiments presented in the table is the coherent detection. As a matter of fact, the additional sensitivity provided by coherent detection is an impor- tant plus in 100 Gbit/s systems. Coherent receiver is generally realized by digital signal processing, SO that an Analog to Digital converter at a speed of the order of 50 GHz is generally employed immediately after the detection. In the table, there is one Ultra Long Haul system, conveying an impressive capacity by the use of both C and L band. The line site of this system is exactly like the scheme of Figure 6.28, but for the presence of three Raman pumps, which are needed to have a flat gain over all the huge exploited bandwidth, and the fact that two EDFA in parallel provides gain in C and 