# Optical Channel Selection Avoiding DIPP in DSB-RFoF Fronthaul Interface
## 4 Simulation Results
Figure 22: Example radio power spectrum of RF signal (\(f_{\text{RF}}\) = 60 GHz, 4096 subcarriers, \(\mu\) = 2, 1.835 Gbps, \(\Delta f_{\text{RF}}\) = 247.7 MHz): (**a**) input signal; (**b**) output signal transported over G.655D fiber in optical channel no. 26 (195.7 THz); (**c**) output signal transported over G.655D fiber in optical channel no. 14 (194.5 THz). Figure 25 shows the constellations of a 64-QAM modulated signal on each OFDM subcarrier in the baseband. In this case, the signal comes from an OFDM demodulator to which 4096 subcarriers were provided on a frequency channel with a width of 491.5 MHz. Such a channel width indicates that a numerological parameter with a value of 3 was used. The propagation conditions in a single-mode fiber, in this case, are much more difficult. This manifests itself in the rapidly changing position of the constellation points in the interval, in the case of the optical channel located on the edge of the 10 dB optical band (Figure 25b). In order to fully verify the correctness of the selection in the computational part of 10 dB optical subbands, suitable for transmitting radio signals in the RFoF format in the DSB version, simulations were carried out with the selected, previously mentioned, optical fibers and system parameters. The simulation results are presented in Figures 26 and 27. Figure 23: Example constellations of 256-QAM signal (\(f_{\rm RF}\) = 60 GHz, G.655D fiber, \(\mu\) = 2): (**a**) demodulated output signal transported over G.655D fiber in optical channel no. 26 (195.7 THz); (**b**) demodulated output signal transported over G.655D fiber in optical channel no. 14 (194.5 THz). Figure 24: Example radio power spectrum of RF signal (\(f_{\rm RF}\) = 60 GHz, 4096 subcarriers, \(\mu\) = 3, \(R_{b}\) = 2.752 Gbps, \(\Delta f_{\rm RF}\) = 491.5 MHz): (**a**) input signal; (**b**) output signal transported over G.655D fiber in optical channel no. 26 (195.7 THz); (**c**) output signal transported over G.655D fiber in optical channel no. 14 (194.5 THz). Figure 27: Simulation results presenting SER as a quality parameter of the selected CP-OFDM signals transported over the G.655D non-zero dispersion-shifted single-mode fiber fronthaul (\(L\) = 20 km): (**a**) for radio carrier \(f_{RF}\) = 60 GHz and the calculated optical 10 dB subband: 194.5130–196.7255 THz; (**b**) for radio carrier \(f_{RF}\) = 28 GHz and the calculated optical 10 dB subband: 184.4880–191.1068 THz. Figure 20:0 Example constellations of 64-QAM signal (\(f_{\rm RF}\) = 60 GHz, G.655D fiber, \(\mu\) = 3): (**a**) demodulated output signal transported over G.655D fiber in optical channel no. 26 (195.7 THz); (**b**) demodulated output signal transported over G.655D fiber in optical channel no. 14 (194.5 THz). Figure 20:1 Simulation results presenting SER as a quality parameter of the selected CP-OFDM signals transported over the G.652D/G.657A single-mode fiber fronthaul (\(L\) = 20 km): (**a**) for radio carrier \(f_{RF}\) = 60 GHz and the calculated optical 10 dB subband: 193.1630–194.7505 THz; (**b**) for radio carrier \(f_{RF}\) = 28 GHz and the calculated optical 10 dB subband: 190.0130–197.2505 THz. In the case of the optical path based on the G.652D/G.657A fiber, the radio signal was used in three modulation configurations with 16-QAM and 64-QAM modulation orders and a numerological parameter with a value of 2 and 3. Figure 27 shows the results of the simulation of radio signal transmission over an optical path based on the G.655D standard fiber. In this case, the tests were performed for 16-QAM, 64-QAM and 256-QAM modulation orders, with numerological parameters of 2 and 3. Not all combinations were tested, but the results obtained are sufficient to confirm the correct selection of optical subbands during the theoretical calculations.