ion power of -2 dBm. The power per channel arriving on the APD is -5 dBm, sufficiently far from both sensi- tivity and saturation. Transmission Systems Architectures and Performances We can adopt at the receiver an electronic equalizer similar to that adopted in the 10 Gbit/s case. The dispersion map, is also in this case, based on post-compensation and under compen- sation; the uncompensated differential group delay (DGD) is 500 ps/nm. With the data, we derive from our draft design the ASE power in the optical bandwidth results to be -19.7 dBm, for a total SNo of 23 dB. The ideal SNo is 20.0 dB; thus, taking into account the FEC gain, we have a great space available to accommodate all the relevant penalties. 6.3.2.2.2 Long-Haul Transmission at 40 Gbit/s: Penalty Evaluation The next step of the system design is to evaluate all the penalties and obtain a draft esti- mate of the required, using the penalty addition method. The result is summarized in Table 6.5. The required SNo results to be 22.4 dB that is smaller than the 23 dB obtained from the draft design. In this case, only semianalytical simulation has been carried out, from which the esti- mate of the required SNo is essentially confirmed. 6.3.2.3 Long-Haul Transmission: Realistic Systems Characteristics As a conclusion of this section, it is useful to review the characteristics of realistic long- haul systems as summarized in Table 6.6. The characteristics of three different types of systems are shown, occupying different product segments in the category of long-haul DWDM systems. The first is a system mainly designed for regional and metro-core applications, even if its characteristics allow a pure long-haul application to be feasible. It can convey a large number of different formats and data speed directly on a wavelength, and ring configura- tions are possible both in hub and in standard ring configuration via a flexible OADM. On the other hand, 40 Gbit/s channels are not supported. The second system is a pure long-haul designed to be installed in the 