Research On The Full-duplex Radio Over Fiber System Providing Multiple Services

Optical wireless access technologies can deliver high-speed data and video services to gigabits/seconds, and it has been considered the most promising solution to future wireless access because of the capability of providing huge bandwidth using optical fiber and offer portability and flexibility to end users. Due to the increase of the demand and various of services, future wireless access system needs to provide multi-access ways, including both wired access and wireless access, even the multiple services. To exploit the benefits of frequency and avoid its congestion, simultaneously generate multiband signals (millimeter-wave, microwave and baseband) has become a research hotspot of current correspondence domain. The generation of high quality signals and cost-efficient base-station design are key issues to make hybrid transmission full-duplex ROF system providing multiple services be practical. We investigated these two key techniques by simulation and experiment, specifically including:Firstly, a new hybrid modulation model employing polarization to generate two-tone optical millimeter-wave signals in a single light wave is presented and the feasibility of the relative full-duplex system is demonstrated. Based on the proposed model, we have successfully transmitted two-tone millimeter-waves and baseband signals over 40km SSMF in full-duplex hybrid transmission by simulation.Secondly, a novel scheme employing a cascaded intensity modulator to simultaneously generate multiband signals is proposed. Triple frequency millimeter wave is obtained with twice optical carrier suppression. Based on the proposed model, we have successfully transmitted 60GHz millimeter-wave signal,20GHz microwave signal and baseband signal by simulation.Thirdly, we have experimentally demonstrated a 40GHz radio-over-fiber system using an optical phase modulator along with an intensity modulator to generate an optical millimeter-wave with OFDM signals with full-duplex transmission in optical wireless access network. The experimental results suggest that the power penalty for the downstream and upstream are 0.8dB and 1dB respectively. In the simulated system, wireless signals are carried by dual-first-order sidebands while the one-first-order sideband is reused for uplink. Both upstream and downstream data are transmitted over 50kmSSMF, and the received constellation figures and eye diagrams are all pretty well.