 dispersion Value due to the high input power. and SPM interplay Managed with MLSE as in Figure 5.59 Residual dispersion of 800ps/ nm (300km is 5100 ps/nm) MLSE at the receiver to cancel completely PMD that is very small (less than 2 ps per 400km @ PMD = 0.1 ps/km-1/2) Polarization effects RIN transfer Compare Equation 4.90 with RIN parameters from Tables 5.4 for the pumps and 5.3 for the signal. Smaller impact on DPSK Phase noise Double Rayleigh Phonon induced noise Aging System margin Normal system margin Total w/o FEC FEC gain (RS 255,223) Required SNo (dB) Transmission Systems Architectures and Performances The second observation is that two additional technologies have been added in this dimensioning example: DPSK and pumping of the SSFM, both increasing the cost and the complexity of the system. What has been gained is 35 km, which is not SO much. However, in real applications, if it is very difficult or very expensive to plane in-line amplifiers (like in short submarine links) even 30km can be the difference between realizing a project or not. 6.3.4.3 Single-Span Systems with Electronic Pre-Distortion at 10 Gbit/s In the case in which electronic pre-distortion is used, as far as the link length is within a few hundred kilometers and no complex device is in line, it can be assumed that single- channel nonlinear effects and dispersion are completely compensated but for a fraction due to the imperfect working of the pre-distortion (finite number of bits, finite dimension of the look-up table, finite adaptation time, and SO on; Table 6.17). This uncompensated part of dispersion and nonlinear effects does not imply a penalty greater than 0.3 dB on the overall system performances at 40 Gbit/s, and an even smaller penalty at 10 Gbit/s. Thus, the system architecture can be very simple: a single-stage EDFA booster at the transmitter and a single-stage EDFA preamplifier at the receiver, IM modulation and detection via a PIN diode due to the small loss between the preamplifier exit and the pho- todiode (essentially t