SK 100 Gbit/s signal performs quite better with respect to the original binary 40 Gbit/s signal for which the link was designed. This is mainly due to the smaller value of the signal optical bandwidth, which is 33 GHz instead of 40 with a remarkable difference of 19%, but also the low value of the required SN has its role. Penalty (dB) All 100 Gbit/s One 100 Gbit/s FIGURE 9.52 Linear crosstalk-induced penalty both in case of a single 100 Gbit/s channel and in case of a complete substitution of Normalized channel spacing (Aw/2nRs) all the channels with 100 Gbit/s. Telecommunication Networks TABLE 9.10 Summary of the Penalty Analysis for the 8-DPSK 100 Gbit/s Designed to Work with a Line Optimized for 40 Gbit/s NRZ 100 Gbit/s 8-DPSK NRZ on a 40 Gbit/s link System length 2000 km Channel speed 100 Gbit/s 8-DPSK-Direct Detection, span length 50km, Standard FEC Channel spacing 200 GHz Extended C band, 38 nm in the third window, that is 4560 GHz, 22 channels at 100 Gbit/s Ideal SN (dB) (B = 4.8Rs) Optical to electrical bandwidth ratio Ideal SN (dB) Margin in dB Transmitter dynamic range DPSK Transponder with phase TiNbLi modulator Linear crosstalk Gaussian selection filter (single stage AWG), Bo = 4.8RS Channel spacing If = 6RS (see Figure 5.2) Nonlinear crosstalk Use of SSMF to thwart FWM, post-compensation with DCF SPM and chromatic 40 Gbit/s optimized dispersion map (see Table 6.5) dispersion interplay Per channel optical and electronic dispersion compensation at the receiver. Used an MLSE equalizer (see Figure 9.49) MLSE equalizer at the receiver Aging System margin Polarization effects Polarization depending losses, connectors misalignments, etc. Total SN post code 27 dB Code gain (dB) Total SN pre-code To verify the transmitted power for SPM assessment To confirm with simulation This example shown as 8-DPSK is quite promising for transmission of 100 Gbit/s signals on links designed for 40 Gbit/s. 9.5.2 Practical Multilevel Systems: Transmitting 100 Gbit/s on a 10 Gbit/s Line by 4QAM This is a much more difficult p