2-dB SNR Gain Enabled by Noise Canceling Filter in Bandwidth Limited Time-Interleaved Digital-Analog Radio-Over-Fiber

We propose a novel noise-canceling filter (NCF) for the fronthaul link based on the time-interleaved hybrid digital-analog radio-over-fiber (TI-DA-RoF) structure. The NC scheme aims to eliminate the correlation between the noise of adjacent samples induced by the equalizer, achieving higher SNR performance in bandwidth limitation conditions. We utilize the noise extracted from the digital part to cancel the color noise of the analog part using an NCF. The filter taps are obtained through a training sequence and then utilized to cancel the noise of the analog part using the noise of the digital part obtained through the decoding process. We conduct a numerical analysis to demonstrate the effectiveness of the NCF in different bandwidth channels. In the experiments, we employ an IMDD-based DA-RoF system to demonstrate the effectiveness of the NCF in the QAM-1024 RoF system. The NCF achieves a 2-dB SNR gain for the wireless signal, enabling high 92-Gbaud DA symbol rate transmission with an SNR threshold of 32 dB. We achieve a CPRI-equivalent rate of 920 Gbps and a capacity of the equivalent fronthaul channel of 244.81 Gbps in QAM-1024 wireless transmission. The results show a promising solution for the future beyond-5G/6G (B5G/6G) fronthaul networks.