 compensation is implemented. (After Killey, R.I. et al., IEEE Photon. Tech. Lett., 17(3), 714,2005.) Telecommunication Networks y = =(1/(W km)). No optical dispersion compensation is implemented along the line and conventional EDFAs are used. Information is coded and decoded through RZ IM-DD format without any line code and FEC. The dotted line represents the system performances with perfect dispersion compensa- tion and no compensation of nonlinear distortion. From this curve, it is evident that the system suffers a great performance degradation from nonlinear effects. The solid curves represent penalty in the presence of nonlinear compensation with dif- ferent orders of the look-up table addressing space (indicating the dimension of the look- up table). The performance becomes better and better with the progressive reduction of the difference between the ideal inverse propagation filter and the real processing imple- mented through the look-up table. The better curve is near the dashed line that represents the modulator limit. 6.3.2.1.3 Erbium-Doped Optical Fiber Amplifier Amplified Systems Design: Example of Draft Design Here we want to apply the rules we have given in the previous sections to carry out an example of draft design of a long-haul DWDM system. Starting from 10 Gbit/s, we state at the beginning not to use L band to avoid a too costly system. Since L band channels are separated by C band in the fiber and require different amplifi- ers, the example can be easily extended to a C+L band system, only adding bands splitters when needed and all the components for L band processing. Extended C band can allocate 90 channels at 10 Gbit/s with a spacing of 50 GHz on the ITU-T grid; thus, we will select this option as a good trade-off between cost and capacity. We also select a span length of km. With the amplifiers characteristics of Table 6.2 this is an intermediate span length (the maximum would be km). Good quality array waveguides (AWGs) are used to multiplex and demultiplex the opti- cal channels SO to