High-Speed and Uninterrupted Communication for High-Speed Trains by Ultrafast WDM Fiber–Wireless Backhaul System

We developed a high-speed and handover-free communication network for high-speed trains (HSTs) using an ultrafast and switchable wavelength-division multiplexing fiber-wireless backhaul system in the W band. We successfully transmitted approximately 20-Gb/s and 10-Gb/s signals over the switched fiber-wireless links in the downlink and uplink directions, respectively. An ultrafast radio-cell switching of less than 10 μs was experimentally demonstrated in both downlink and uplink directions. Moreover, the possibility of connecting a central station to many remote radio cells was evaluated, confirming that an uninterrupted communication network up to several tens of kilometers can be achieved for HSTs. The proposed system can overcome the current challenges in mobile networks and can provide a potential solution for the provision of advanced services to users on HSTs in future 5G and beyond networks.