ptimized for 10 Gbit/s NRZ 8-PolSK Phenomenon Notes Link length (km) Max number of channels 9Tbit/s capacity Ideal SN (dB) Electrical to optical bandwidth ratio NRZ transmission Ideal SN, Signal dynamic range Higher modulators screening and accurate balance in the design. Linear crosstalk Channel spacing 100 GHz Nonlinear crosstalk SPM dominant regime, XPM can be neglected Intersymbol interference (SPM, DGD, PMD) Nonlinear polarization Due to the modulation format Polarization dependent losses and A few of polarization effects are considered in detail other effects Aging System margin Total w/o FEC FEC gain (Turbo Code) Required SNo Telecommunication Networks This lack of margin is not really important since we have to remember that a margin of 3 dB is already inserted in the penalty analysis. On the other hand, the simulation is a bit better than the penalty analysis, confirming the system feasibility. 9.5.4 Practical Multilevel Systems: Native 100 Gbit/s Ultra-Long Haul Systems The last dimensioning exercise we will do is the design of a native ultra long haul 100 Gbit/s system. 9.5.4.1 Draft Design We will use Raman-assisted transmission and the scheme of the generic system span will coincide with that of Figure 9.61, a familiar scheme from Chapter 6, but without in- line Erbium Doped Fiber Amplifiers (EDFAs). The only EDFA is present as booster at the transmitter. The intention is to limit the ASE as much as possible and to maintain a low power along the line to control nonlinear effects. We will also adopt a span length of 30km in order to decrease the ASE power as much as possible. The line results to be composed of 257 spans, each of which is formed by 30 km of SSMF and 5 km of DCF pumped to obtain Raman gain. The Raman pumps are extracted at the DCF end SO that propagation in the SSMF is completely passive. The whole system is thus 9000 km, long. Since the design is inspired to a submarine application, no OADM is foreseen in the nodes. As far as modulation is concerned, we select constant power 16-4QAM wi