## 3 Performance Evaluation-Simulation Results  
To evaluate the HROPA performance, we use a two-step modeling and simulation methodology. First, we implement a MATLAB-based model of the equations described in Section 2 to calculate the best choices of OPA and Raman pump powers and wavelengths. In particular, first, we perform parametric runs for the OPA pump wavelength to achieve the optimum gain bandwidth. Then, we perform parametric runs to optimize the OPA pump power. Following that, we evaluate the optical power of the Raman pumps that will minimize gain ripple. The HNLF parameters that we used in our simulation are \(\lambda_{o}=1340\) nm, \(\gamma=11.67\) W\({}^{-1}\)/km, \(\beta_{3}=0.049\) ps\({}^{3}\)/km and \(\beta_{4}=2.35\)\(\times 10^{-6}\) ps\({}^{4}\)/km [15]. In our simulation, we consider the small signal regime (e.g., \(\leq-28\) dBm), and we ignore the signal to signal interactions. The model takes into account the insertion losses of the different passive components and the fiber, as well as the filters' transfer functions. The OPA pump wavelength at 1340.2 nm and the HNLF length \(L_{\text{p}}=150\) m for HNLF2 were selected, such that we cover the gain bandwidth of 170 nm (1264 nm-1436 nm). We find that the optimum OPA pump powers are \(P_{\text{Pl}}=2.52\) W (upper band) and \(P_{\text{P2}}=2.3\) W (lower band) to achieve the target gain of 20 dB. The Raman pump powers of \(P_{\text{R1}}=1.1\) W at 1260 nm and \(P_{\text{R2}}=0.63\) W at 1280 nm were selected with \(L_{\text{R}}=500\) m for HNLF1 to obtain a minimum ripple. We obtained a signal gain of \(\geq\)20 dB and a gain ripple of \(<\)4 dB using the aforementioned parameters, as shown in Figure 6a. The dip in the spectrum is due to the filtering of the OPA pump wavelength. The second step of our methodology is performed using the simulation tool, Synopsis RSoft, where we build a simulation model of the HROPA design with the selected wavelength and optical pump powers from the first step. The simulations performed in Synopsis RSoft include all possible degrading effects in the system (e.g., fiber dispersion, fiber attenuation, stimulated Brillouin scattering (SBS), Rayleigh backscattering, interchannel and intrachannel crosstalk and amplified spontaneous emission noise). We obtained the noise figure (NF) using Synopsis RSoft, shown in Figure 6b. As can be seen in Figure 6b, the NF ranges from 1.5 to 11.5 dB. Since the center of the band is Raman amplification dominated, the NF is lower than in the edges, where the noise figure is OPA dominated. As we described in Section 2, the splitting and combining of the two bands is achieved using standard WDM DEMUX and MUX components. Hence, due to their non-ideal band-to-band or channel-to-channel isolation, crosstalk terms may be present in the system. There are two types of crosstalk terms that may propagate through the system and can end up at the receiver and, hence, affect the amplifier performance. The first one is due to the non-ideal performance of the WDM DEMUX, which allows for some leakage of the upper-band signals to the lower arms and _vice versa_. The second set of crosstalk terms is due to the generation of the idlers at the OPA sections and their leakage through the WDM MUX. Note that these crosstalk terms may be further suppressed by the CWDM DEMUX that routes the signals to the desired path. However, the degree of crosstalk suppression depends on the relative difference of the crosstalk wavelengths to the pass band of the CWDM DEMUX. To further understand the potential limitation posed by the presence of the crosstalk terms and their impact on the performance of the HROPA, we present a worst-case scenario analysis and characterize the impact on the amplifier performance. We define the signals, idlers, and leakage terms as:  
Signals:  
* Su: upper-band signals,
* S\({}_{\text{L}}\): lower-band signals. Idlers:  
* isu: idlers correspond to upper-band signals,
* isl: idlers correspond to lower-band signals.