taking into account that a margin has to exist between the draft design SN and the requirements derived from the penalties analysis, SO to accommodate the approximation uncertainty that will become clear with the simulation results. The difference in performances is mainly in the different role of nonlinear effects, as it can be clearly deduced by the table. In order to better appreciate the reason of this difference, the signal power behavior in a single span of the hybrid system is shown in Figure 6.29. It is clear how the average power along the transmitted line is much lower using distrib- uted Raman amplifiers even if the optical power entering into the EDFA at the span end (i.e., into the preamplifier in front of the receiver) is the same in both cases. Transmission Systems Architectures and Performances TABLE 6.9 Penalty Analysis of the Ultra-Long-Haul 10 Gbit/s System Realized with Two Different Architectures: Hybrid Amplification and All Erbium-Doped Optical Fiber Amplifier Amplification Ultra-Long-Haul 10 Gbit/s Transmission EDFA Only Hybrid Phenomenon Notes Notes Ideal SN (dB) (Be=2R) Electrical to optical RZ with a duty RZ with a duty cycle of bandwidth ratio (Moe) cycle of 25%, Be 25%, Be 2 R, B = 4R = R, B = 4R Ideal SNo Signal dynamic range Lithium niobate Lithium niobate modulator modulator-Raman dynamic compression Linear crosstalk AWG multistage, AWG multistage, spacing 2.5 spacing 2.5 signal signal bandwidth bandwidth Nonlinear crosstalk FWM and XPM Smaller average power (see Equation due to Raman 4.45) SPM-DGD interplay RZ reduces Smaller average power relative penalty due to Raman-RZ effect 10ps, FFE-DFE at the compensated by receiver to cope with the FFE-DFE at PMD (See Figure 5.57) the receiver (See Figure 5.57) Polarization effects RIN transfer Non-applicable Compare Equation 4.90 with RIN parameters from Tables 5.4 for the pumps and 5.3 for the signal Double Rayleigh Non-applicable Photon induced noise Non-applicable Aging System margin Normal system Normal system margin margin Total w/o 