ating the noise terms. Naturally, pump depletion is taken into account while analyzing Raman gain. The noise power is evaluated analytically and the saddle point approximation is used to estimate the error probability. The results of this simulation integrated with margins and aging confirm in all the con- sidered cases the draft design with a good. TABLE 6.10 Penalty Analysis of the Ultra-Long-Haul 40 Gbit/s System 40 Gbit/s Ultra-Long-Haul Hybrid-40 Gbit/s Phenomenon Notes Ideal SN (dB) (Be = 2R) Electrical to optical bandwidth ratio RZ modulation 33% Ideal SNo Signal dynamic range Lithium niobate modulator Linear crosstalk AWG multistage-B,=2R Nonlinear crosstalk FWM and XPM SPM and DGD interaction Added electronic compensation 4.72 ps, compensated by the FFE-DFE at the receiver Polarization effects RIN transfer Double Rayleigh Phonon induced noise Aging System margin Normal system margin Total w/o FEC 31.8 dB FEC gain (RS 255,223) Required SNo 25.8 dB Telecommunication Networks Up to now, we have underlined all the advantages of the use of hybrid amplification. However, there are also a set of issues that explain the fact that pure EDFA DWDM systems are the most diffused products on the market till today. The first and more important point is that using Raman amplification requires high power pumps with all the induced thermal management and high operational expense related to power consumption. It is important to remember from Chapter 2 that, in general, the main goal of carriers is to decrease the operational cost (OPEX) of the network, more than increasing the perfor- mances of the transport layer. When deploying an ultra-long-haul system, the greater cost related to operational expenses and to the higher system cost per km and per Gbit/s have to be compared with the costs implied by realizing the link with a cheaper long-haul system, using an interme- diate electronic regenerator. Also, from the security point of view, operating systems with such powerful lasers put some problems in the procedures for uni