Ultrabroadband Wireless–Optical Transmission Links Using Axial Slot Leaky Feeders and Optical Fiber for Underground Transport Topologies

This paper describes a hybrid leaky feeder/fiber-optic transmission system for use in underground transportation networks. The system has a 1.6-Gb/s throughput and features an ultrawideband axial slot leaky feeder, which is based on a standard semirigid coaxial cable as a fixed antenna. Patch antennas with a 4-GHz center frequency and a 1-GHz, -10-dB bandwidth are proposed for the rolling stock. This highest reported data rate was achieved by combining two 800-Mb/s in-phase and quadrature (I and Q) phase-shift keying (PSK) modulated data streams. A specially designed carrier and data synchronization system provided a convenient interface to a 1.3/1.5-mum diplex single-mode fiber-remoting network. The measured 2.4- to 6-GHz leaky feeder bandwidth allows multiradio multiband wireless mesh networking and, therefore, low-contention gigabit rolling stock data communications.