## 4 Optical and Radio Frequency Measurement Analysis
### Optical Measurements Analysis
Similar results can be obtained for the EDFA-based link since the conversion efficiency of the PPC is similar for the 1550 nm wavelength. Figure 5 illustrates the optical power available at the input of the PPC module at the remote station (Figure 1) for different fiber lengths and for the Raman-based link (Figure 5a) and the EDFA-based link (Figure 5b). The orange horizontal lines represent the maximum input optical power to respect the safety limit of the PPCs, which is required to obtain 356 mW of electrical power at the output of the PPC module. The green horizontal line represents the minimum input optical power required to meet the 263 mW electrical power threshold necessary for the proper operation of the remote station's electronic components. For the Raman-based link, only the 5 km fiber length satisfies both the minimum and maximum power requirements at the PPC module input. In contrast, for the EDFA-based link, fiber lengths of 5 km and 10 km meet these power constraints. Since these links can achieve an input power above the maximum optical power of 32.1 dBm, the PPC module can be reconfigured with a \(1\times 16\) optical splitter to enhance optical power reception at the Remote Station. Figure 4: Electrical power available at the output of the PPC module at the remote station for a 5 km fiber length. Figure 5: Optical power available at the input of the PPC module at the remote station (**a,b**). * Radio frequency measurement analysis  
The RF measurements were conducted using a 5 GHz RF signal with a continuous wave (CW). The LNA1 has a gain of 24 dB with a NF of 1.9 dB, connected to the MZM input with a \(V\pi\) of 5.2 V. The gain of the LNA2 is 35 dB, with a NF of 1 dB, connected after the PD with a responsivity of 0.65 A/W. An RF generator is used instead of the antenna to feed the MZM RF input with a power of 0 dBm. Figure 6 shows the RF gain, NF, and SFDR measurement results of the links with Raman-based and EDFA-based HPLS, considering the three fiber lengths. Figure 6a presents the measured RF gain at various HPLS power levels, calculated using Equation (1). The RF gain is directly related to the Raman gain behavior shown in Figure 2. The maximum gain achieved was 22.6 dB for a fiber length of 15 km with a Raman-based HPLS and an input power of 34 dBm. However, high gains do not necessarily indicate good NF values. As the length of the fiber and the HPLS power increase, optical amplification due to stimulated Raman scattering can produce high levels of ASE noise and RIN transfer, which degrades the NF of the system. By applying Equation (2), it is possible to define the measured noise figure (Figure 6b). For the Raman-based HPLS and for lengths of 5 km, 10 km, and 15 km, the NF starts to increase from the input HPLS powers of 35 dBm, 33 dBm, and 32 dBm,  
Figure 6: Measured RF gain, noise figure, and SFDR for the Raman-based and EDFA-based setups. respectively, although the RF gain continues to increase. The same effect can be observed for the EDFA-based HPLS, with lengths of 10 km and 15 km. Through Equation (3), it is possible to define the measured SFDR (Figure 6c). The SFDR begins to decrease at the same HPLS power level as the NF increases for different fiber lengths because of the strong relationship between the SFDR and NF, as shown in Equation (3). The RF results presented in Figure 6 are validated by comparing the experimental and theoretical results. Using Equations (4)-(6), it is possible to calculate \(\mathrm{G}_{\mathrm{RF}}^{\mathrm{T}}\), \(\mathrm{NF}^{\mathrm{T}}\), and SFDR\({}^{\mathrm{T}}\), which are shown in Figure 7 for the 10 km Raman-based and EDFA-based links. In Figure 7a-c, the green dots and black lines represent the experimental and theoretical results, respectively, for the Raman-based link. Similarly, the red dots and blue lines represent the experimental and theoretical results of the EDFA-based link.