Design and analysis of continuous spectrum-based nonlinear frequency division multiplexing integrated with radio over fiber network

Radio over Fiber (RoF) is a hybrid wireless technology that integrates radio frequency and optical fiber networks to enhance channel capacity. However, fiber nonlinearity remains a major limitation, particularly under high-capacity and high-power operation. With the transition from 5G to 6G systems, mitigating this nonlinearity has become critical, as these networks utilize higher-order modulation formats requiring increased signal power, which in turn degrades system performance. To address this challenge, a Continuous Spectrum (CS)–Nonlinear Frequency Division Multiplexing (NFDM)-based RoF system is proposed. The CS-NFDM-RoF model effectively mitigates nonlinear impairments, improving performance under 5G/6G conditions. Comparative results show that it outperforms the conventional Orthogonal Frequency Division Multiplexing (OFDM)-RoF system. For 16-Quadrature Amplitude Modulation (QAM), it achieves an Error Vector Magnitude (EVM) gain of 3.91 dB over 100 km and a peak Q-Factor improvement of 2.88 dB, enabling a data rate of 25.6 Gbps. For 64-QAM, it provides a 4.2 dB EVM gain over 50 km, supporting a data rate of 38.4 Gbps.