decreasing the number of channels SO that the available power can be distributed among fewer channels. In both cases naturally, great attention has to be paid not to increase the power per chan- nel too much to generate a high penalty due to nonlinear effects. Here we imagine, as almost always in practical systems, that amplifiers configuration can be controlled within certain limits via the system element manager. As already done in the case of 40 Gbit/s transmission (see Chapter 6), we reconfigure the in line amplifiers SO to decrease the output power up to 18.5 dBm. Moreover we divide by half the number of channels fixing to 100 GHz the channel spacing. This contemporary increases the power per channel at the output of in line amplifiers up to 2 dBm and takes under control linear and nonlinear crosstalk that otherwise will increase due to the passage of the optical signal bandwidth from 10 to 16.6 GHz. The resulting configuration conveys in any case the huge capacity of 4.5 Tbit/s, with an upgrade of a factor 5 with respect to the 900 Gbit/s of the original system. The SNo calculated from the power budget increases to 30 dB, taking into account 11 dB of super FEC gain thus providing a margin of 5 dB to allocate penalties. 9.5.2.2 Penalties Analysis As usual in this section all the relevant penalties coming from the different system impair- ments are evaluated and added to verify that the overall SNo is sufficiently high to guaran- tee a correct system working. 9.5.2.2.1 Transmitter Dynamic Range Due to the small margin available, the transmitter is particularly accurate, reducing the dynamic range penalty from 1 dB, which is considered a standard transmitter perfor- mance, to 0.3 dB. This is done with an accurate balance of dual arms modulators used in the transmitter [32]. 9.5.2.2.2 Linear Crosstalk We have an optical bandwidth of the transmitted signal of 16.6GHz with a spacing of 100 GHz and a Gaussian filter of GHz. Thus the ratio between the optical bandwidth and the symbol rate is 1.2 and the normalized 