Integration between fiber-optic and wireless communications systems in the "last mile" access networks is currently considered as a promising solution for both service providers and users, in terms of minimizing deployment cost, shortening upgrading period and increasing mobility and flexibility of broadband services access. To realize the seamless convergence between the two network segments, the lower capacity of wireless systems need to be increased to match the continuously increasing bandwidth of fiber-optic systems. The research works included in this thesis are devoted to experimental investigations of photonic-wireless links with record high capacities to fulfill the requirements of next generation hybrid optical fiber-wireless access networks. The main contributions of this thesis have expanded the state-of-the-art in two main areas: high speed millimeter-wave (mm-wave) communication links and radio-over-fiber (RoF) systems employing wireless multi-input multi-output (MIMO) multiplexing technologies. Regarding high speed mm-wave links, this thesis focuses on high capacity fiber-wireless transmissions in both the V-band (50-75 GHz) and the Wband (75-110 GHz). Photonic mm-wave signal generation techniques with both coherent and incoherent optical sources are studied and demonstrated. Employments of advanced modulation formats including phase-shift keying (PSK), M-quadrature amplitude modulation (QAM) and orthogonal frequency-division multiplexing (OFDM) for high speed photonic-wireless transmission are experimentally investigated. Furthermore, this thesis also studies the implementation of bidirectional operations in hybrid optical fiber-wireless systems. In addition, this thesis proposes and demonstrates the seamless translation of both fiber wavelength division multiplexing (WDM) and polarization multiplexing (PolMux) RoF systems into wireless MIMO links, to increase the spectral efficiency and overall throughput of bandwidth limited fiberwireless systems. Two different modulation formats: MIMO-OFDM and MIMO-quadrature PSK (QPSK), are experimentally investigated based on different channel estimation techniques. In conclusion, the results presented in the thesis show the feasibility of employing mm-wave signals, advanced modulation formats and spatial multiplexing technologies in next generation high capacity hybrid optical fiber-wireless access systems.
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Vegas Olmos, Juan José, Forchhammer, Søren, Tafur Monroy, Idelfonso