SMF, 40km DCF Channel number Extended C band Channel spacing Modulation format RZ 40% Gaussian pulses Ideal SN, (dB) Bo/Be (due to RZ modulation) 4 @ 10 Gbit/s, RZ modulation with 40% duty cycle Required SN, (dB) Impairment Penalty (dB) Notes APD receiver noise This is mainly the avalanche noise (see Equation 5.29), due to the low power on the APD (-20 dBm per channel) Signal dynamic range Lithium niobate modulator- Raman dynamic compression Linear crosstalk AWG multistage, signal spectrum Gaussian with unilateral spread of 25 GHz, Gaussian optical filter with 25 GHz width, see Figure 6.16 Nonlinear crosstalk (FWM XPM) Wide spacing (100GHz) and use of an SSMF Residue chromatic dispersion Value due to the high input power. and SPM interplay Managed with Use of RZ modulation (paying a larger Bo) MLSE as in Figure 5.59 Residual dispersion of 1200 ps/ nm (300km is 5100ps/nm) Pre-chirp at the modulator as in Figure 6.9 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 Table 5.4 for the pumps and 5.3 for the signal Double Rayleigh Phonon induced noise Aging System margin Normal system margin Total w/o FEC FEC gain (RS 255,223) Required SNo (dB) Telecommunication Networks (6.92) e3(t)=e4(t)= Differential encoding allows a very simple direct detection to be performed for DPSK sig- nals through the receiver whose scheme is shown in Figure 6.33. The incoming signal is split with a standard beam splitter; one of the outputs is delayed a bit time T and then the two fields are recombined with another beam splitter. Starting from (6.91) it is easy to see that, after traveling through an amplified line, the photocurrent has the following expression: c(t) = osb)Nn(t (6.93) where N'ASE(t) = being MASE the optical noise process, nT(t) is the Heaviside function as defined earlier, P is the received optical power, and R the photodi- ode responsivity. Finally, ng(t) is the electrical and sho