800-MHz Bandwidth Signal Transmission with Radio over Multi-Mode-Fiber for Cascaded IFoF-Based C-RAN Mobile Fronthaul

We report the signal transmission with an analog radio over multi-mode fiber (A-RoMMF) subsystem using a single-mode vertical cavity surface emitting laser and a cost-efficient bias-tee consisting of a coupling transmission line with an electrical circuit pattern. The frequency response of the coupling transmission line has a slope inverse to that of the A-RoMMF subsystem at the 28-GHz band to suppress the channel power difference of two component carrier signals for 800-MHz bandwidth signal transmission through a 200-m long multi-mode fiber (MMF). The evaluation was performed using 5th generation new radio (5G-NR) 64 quadrature amplitude modulation (64-QAM) orthogonal frequency division multiplexing (OFDM) signals with a center frequency of 28 GHz, two component carrier (CC), a bandwidth of 400 MHz/CC and subcarrier spacing of 120 kHz. Furthermore, we demonstrate the transmission of 5G-NR 64-QAM OFDM signals with two carrier component, a bandwidth of 400 MHz/CC and subcarrier spacing of 120 kHz signals when the novel A-RoMMF subsystem is adapted to a cascaded intermediate frequency over fiber based centralized radio access network mobile fronthaul system with a 200-m long MMF and 5-m distance wireless transmission.