## 3 Heterogeneous MLR Network of the NG-PON Type  
For the assembly of this heterogeneous network, Figure 2, the first 2.5 Gbps channel was focused on 193.7 THz, and the remaining three successively separated by 25 GHz, a value that was concluded, when conducting tests, to identify the minimum spacing between channels so as not to affect signals. Subsequently, the 10 Gbps channel was located separate from the fourth 2.5 Gbps channel by 25 GHz, and, finally, the 40 Gbps channel with a 100 GHz separation. An ideal precompensation of the accumulated total chromatic dispersion was performed in the system 100% using a Bragg grid compensator and a length of 80 km for the distribution network and 500 m of fiber for the last mile was handled, using a power of 0 dBm for the 2.5 Gbps channels and 40 Gbps, and 5 dBm for the 10 Gbps. Finally, it will work with a target bit error rate (BER) of \(10^{-9}\) or less, according to the ITU-T recommendations. Figure 3a,b shows the optical spectra in transmission and reception, respectively, of the first 2.5 Gbps channel, where there is evidence of a decrease in signal intensity, but no interference from other channels; the same happens with the three remaining channels. The 10 Gbps channel, adjacent to the 2.5 Gbps channel four, is affected by it, as shown in Figure 4a,b, while, the second channel has no effects on its spectrum due to the fact that it has enough spacing so that its counterpart and the 40 Gbps channel have no impact on it. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Phases** & \multicolumn{2}{c}{**Model Variables**} \\ \hline \multirow{4}{*}{OLT} & Modulation formats & NRZ-OOK, RZ-OOK, RZ-DPSK \\ \cline{2-3}  & & Maximum allowable to maintain a \\  & Optical channel power & predominantly quasilinear \\  & & propagation regime \\ \cline{2-3}  & Nominal access & 2.5 Gbps, 10 Gbps, 40 Gbps \\ \hline \multirow{4}{*}{ODN} & Optical channel spacing & depends on the factor \(\Delta_{v}\) \\ \cline{2-3}  & Link distance & 80 km \\ \cline{2-3}  & Number of channels & Maximum allowable to achieve a higher \\  & Throughput of a NG-PON2 network. \\ \cline{2-3}  & Length extensions & EDFA if required for minimum distance. \\ \cline{2-3}  & Type of service & FITH \\ \cline{2-3}  & Link type & DL- Unidirectional \\ \hline \multirow{2}{*}{ONU} & Number of users last mile & 32 \\ \cline{2-3}  & Splitter & 4:1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Model variables. Figure 4: Optical Spectra, 10 Gbps First Channel. (**a**) Optical spectrum in transmission; (**b**) Optical spectrum at reception. Figure 3: Optical Spectra, First Channel 2.5 Gbps. (**a**) Optical spectrum in transmission; (**b**) Optical spectrum at reception. Figure 2: Network scheme. In the 40 Gbps channel, a small de-formation is observed to the left of the optical spectrum, which corresponds to the interference caused by the adjacent 10 Gbps channel. It should be noted that the spacing between the second 10 Gbps channel and the 40 Gbps channel is not sufficient for the lower speed channel not to affect the optical spectrum of the higher speed channel, but it does not affect data transmission, achieving a BER of \(10^{-40}\) for both channels, Figure 5a,b. In this network model, it was possible to transmit 70 Gbps in a bandwidth of 271.212 GHz, as shown in Figure 6.  
In the optical spectrum of the throughput Figure 7, the seven transmitted channels are observed, managing to differentiate the characteristic of the signal of each of the different modulations and speeds, as well as small additional channels which can coincide with an original channel producing distortion or loss of information, as a product of the four-wave mixing (FWM) effect or four-wave mixing, this means that, at some point, the transmitted signals go into phase coincidence. Figure 5: 40 Gbps channel optical spectra. (**a**) Optical spectrum in transmission; (**b**) Optical spectrum at reception. Figure 6: Ideal throughput optical spectrum.