| As one of the most important applications of microwave photonic, ROF (Radio over Fiber) system, which combines the advantages of optical communication and wireless communication, is a good candidate for broadband mobile communication. Under the supports of the National Nature Science Foundation of China and the Ph.D. Programs Foundation of Ministry of Education of China, some key technologies for millimeter-wave generation and transmission is analized and verified by simulation or experiment in this thesis. And the main achievements of this thesis are listed as follows:1. According to the theoretical model of laser noise and simplified additive noise, the impact of millimeter-wave (mm-wave) generation and demodulation caused by fiber dispersion is analysed by using the stochastic signal transmission theory. The impact of mm-wave generation and demodulation caused by polarization mismatch is also discussed. A dual-wave laser incorporating a homemade polarization maintaining fiber Bragg grating (PMFBG) is used to generate microwave signals with frequencies around22GHz. The experimental results verify our theoretical analysis.2. A parallel structure of Mach-Zehnder Modulator (MZM), which can be used for generating mm-wave via frequency octupling, is proposed. Based on the proposed structure, a bidirectional ROF system, which is capable of generating and transmitting frequency quadrupling mm-wave signal for downlink and providing down conversion frequency components for uplink, is investigated. In the system, the rate of spectrum usage efficiency as high as100%can be achieved. The study results of the proposed scheme demonstrate that it can offer realistic solutions to support future broadband wireless systems.3. A scheme based on a MZM which is driven by triangular wave instead of sine-wave is theoretically proposed. With signal to noise ratio higher than20dB, an mm-wave with multiplication factor (MF) of10is generated. Based on the60GHz mm-wave generation, a ROF downlink transmission performance is evaluated. The result verifies that the scheme is capable of improving the multiplication factor in optical frequency multiplication (OFM).4. An optical single sideband modulation ROF system, by using a homemade acousto-optic filter, is proposed and demonstrated. The carrier to sideband ration is reduced from9.73to2.9dB, and the receiving sensitivity improved from-23.43to-31.18dBm at BER of10-9with30km long SMF. This scheme effectively reduces the influence of the fiber dispersion, and provides a simple, low-cost solution for improving the ROF system performance.5. An OFM with MF as high as16and a tunable ROF system are proposed. The theoretical models of the OFM and ROF system are built by using homemade PMFBGs. Based on the models, the principles are analysed and these two schemes are verified by evaluating the system performances. |
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