Research On Simultaneous Transmission For Both Wired And Wireless Signals In Radio Over Fiber System

Recently, the demands for high data rate and bandwidth of wireless and wired-line systems have rapidly increased. Next-generation access networks are committing to convergence the wired and wireless services into one way. Raio-over-Fiber systems, simultaneously providing services for both fixed and mobile users, have become a research hotspot of current correspondence domain. Both hybrid modulation schemes for wired and wireless signals and cost-efficient base-station design are key issues to make hybrid transmission full-duplex ROF systems be practical. We investigated the two key techniques by simulation and experiment. Specifically including:Firstly, a new hybrid modulation model employing an integrated modulator with remote delivery local-oscillator signal is presented and the feasibility of the relative full-duplex system is demonstrated emulationally. Based on the proposed model, we have successfully transmitted downstream signals, which mixed by 2.5Gbit/s wired-line data and 633Mbit/s PSK wireless data, over 50km SSMF to the base-sation(BS) with remote delivery 40GHz local-oscillator(LO) signal.Secondly, a novel scheme employing a dual-arm Mach-Zehnder modulator (MZM) to simultaneously generate wired and wireless signals with remote delivery optical LO signal is proposed. At the BS, we use an electro-absorption modulator (EAM) to realize the effectively down-conversion and modulation of upstream data. In the first place, we have theoretically investigated and experimentally demostrated the characteristics of EAM. After 20km transmission over fiber, the power penalty of the down-converted intermediate frequency(IF) is about 3dB. Then we've successfully demonstrated a ROF system employing an EAM, in which symmetric data at 2.5Gbit/s for all of wired and wireless downstream channel and upstream channel, and the transmission distance can reache to 50km ever longer.Thirdly, we have experimentally demonstrated a novel scheme to generate a high frequency optical millimeter-wave by using a single-arm MZM and a full-duplex radio- over-fiber system by wavelength reuse; and we've generated a high frequency optical millimeter-wave in a hybrid access network which can provide wired-line and wireless services simultaneously by simulation. By using a single-arm LiNbO3 modulator, frequency quadrupled optical millimeter-wave has been generated, and we have successfully reused the wavelength in uplink. The power penaly of downlink and uplink are less than 0.5dB and 1.7dB, respectively. In the simulated hybrid ROF system, wireless signals are carried by dual-second-order sidebands while the central carrier is used to carry wired-line signals and then central carrier's wavelength is reused in the base-station. Both upstream and downstream data are transmitted over 50km SSMF, and the received eye diagrams are all pretty well.