## 4 Results and Discussion
For distinct channel spacings such as 12.5, 25 and 50 GHz, the developed model is tested for different values of nonlinear refractive index and BER results are obtained, as mentioned in Figure 11. This figuredemonstrates that RItNLs are managed efficiently at 2.6 \(\times 10^{-17}\) m\({}^{2}\) /W nonlinear refractive index. Figure 12 is obtained by performing the simulations for different data rates per channel, which shows that data rate up to 3.125 Gb/s per user can be supported by lowest channel spacing value of 12.5 GHz, for 32 number of channels. Though an aggregate data rates of 100 Gb/s (32 \(\times\) 3.125 Gb/s) is obtained for all 12.5 GHz channel spacings, the results in Figure 12 show that higher data rates can be achieved using channel spacing of 25 GHz or 50 GHz, as the BER performance is below the threshold for values greater than 3.125 Gb/s user data rate. The BER results for different input optical power levels and received power are presented in Figures 13 and 14 respectively, for different number of channels and at 100 Gbps aggregate data rate. Finally, Figure 15 shows the BER results for different values of nonlinear dispersion parameter. It is clear from the results that the lower value of nonlinear dispersion results in low range of RItNLs. Figure 15 also presents BER for different number of channels by using 25 GHz and 50 GHz channel spacings at 500 km transmission length. Comparing the obtained results with recently published work, the 8 channel WDM system presented in [33; 34; 35; 36] provides transmission up to 25 km with 25 GHz channel spacing, in the presence of FWM non-linearities. Additionally, an advanced receiver presented in [34] enables the 8-channel WDM transmission up to 100 km with 100 GHz channel spacing with BER of 5.3 \(\times\) 10\({}^{-6}\) by mitigating the SPM, XPM and FWM non-linearities. Figure 10: BER results for different fiber lengths with 4, 8, 16, and 32 channels (with 50 GHz channel spacing). Thus, the work presented in this paper is of considerable importance, as it provides lower BER rates for 500 km transmission, 32 channels and 12.5 GHz channel spacing. Figure 11: BER results versus refractive index for 12.5, 25, 50 and 100 GHz channel spacing for 32 number of channels. Figure 12: Data rate per channel with 12.5, 25, and 50 GHz channel spacing, for 16 and 32 number of channels. Figure 14: Receiver sensitivity for 8, 16 and 32 channels after 400 and 500 km of optical fiber transmission. Figure 7:0 BER for different input power levels for 8, 16 and 32 channels with 25 and 50 GHz channel spacing. OSNR achieved in [40] after 500 km transmission through a low loss fiber justifies our BER results and received eye diagram, as explained in the next paragraph. Lastly, we explore the efficiency of the proposed model and its ability to minimize RIrNLs based on the basis of eye-diagrams for different channel spacings. Figure 16a-c shows the results for 12.5, 25, and 50 GHz channel spacing without RIrNLs compensation at 500 km distance cover and 100 Gbps aggregate data rate. While the eye diagrams after RIrNLs compensation are shown in Figure 16d-f, which clearly demonstrates improvement in performance. Figure 7:1 Results for Eye-diagrams; (**a–c**): For 12.5 GHz, 25 GHz, 50 GHz channel spacings, respectively, without RIrNLs compensation, (**d–f**): For 12.5 GHz, 25 GHz, 50 GHz channel spacings, respectively, after RIrNLs compensation. Figure 7:2 Nonlinear dispersion versus BER at 25 and 50 GHz channel spacing, 500 km transmission distance and 8, 16 and 32 number of channels.