Application Studies On Microwave Photonics Technology And Radio-over-Fiber Access Networks

With the booming development of "mobile internet", broadband wireless communication has been treated as the dominant direction for the communication evolution of next generation. While the most enabling technology, microwave photonics, offers the key to realize reliable and cost-effective application of "mobile internet". In this dissertation, we focus on the microwave photonics technology and its main applications in broadband wireless over fiber system, evaluations are carried out in theoretic and experiment. The main topic includes:1. Research on all-optical transformation from NRZ Data to Ultra-Wideband Pulse StreamBased on a special fiber Sagnac structure, we propose and experimentally demonstrate a compact and cost-effective scheme to realize real time conversion from differential nonreturn-to-zero (NRZ) data to ultra-wideband (UWB) pulse stream. Comparing to traditional all-optical UWB signal generation, the proposed scheme reliefs the requirement on using expensive broadband Gaussian pulse generators. Further more, this proposed data format transformer could output UWB pulse streams in real time while OOK data is launched into the input port of the system.2. Research on all-optical approach of microwave frequency measurementAn all-optical approach for microwave frequency (MWF) measurement with a low-speed oscilloscope is proposed and experimentally demonstrated. In this scheme, an optical filter with a single and ultra-narrow passband, together with a tunable laser and a low-speed photodiode is utilized to calculate the MWF by measuring the time delay between the sweeping optical carrier and its upper/lower sideband passing through the filter. Experimental results of single-frequency and multi-frequency measurement show high accuracy and high frequency definition has been achieved.3. Research on full-duplux radio-over-fiber system with compact base stationBased on the special characteristics of the quantum well electro-absorption effect versus different applied external bias, a commercially available electro-absorption modulator is used in a RoF system as a demodulator for the downlink data stream and as a modulator for the uplink stream in a base station at the same time. Experimental results indicate that downlink and uplink data at data rates of100Mbps and50Mbps, respectively, can be transported over hybrid10km fiber and6feet air space with error free. It is noticeable that by applying this proposed approach, the complexity of the base stations could be significantly reduced.4. Research on broadband radio-over-fiber system with compact base station.We propose a novel60GHz broadband radio-over-fiber (BRoF) access system for multi-gigabit bidirectional data transmission. In conventional microwave wireless system designs, expensive high frequency electrical local oscillator (LO) sources are required for frequency conversions in base station (BS) and mobile terminal (MT), incurring considerable cost for system integration and maintenance at millimeter-wave frequencies. We design and experimentally demonstrate a BRoF transport system with compact BS structure, where no electrical LO devices are required. Thus, in this simplified system architecture, the overall cost can be reduced and the operation quality of centralized LO service enhanced. The operation principle and feasibility of error free transmission of multigigabit, bidirectional data streams over both fiber and free space has been demonstrated experimentally. Furthermore, an upgraded version, in support of multi-band services, has also been demonstrated in theoretic and experiment afterwards.