Electrical Computer Engineering

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    PERFORMANCE ANALYSIS OF HYBRID OPTICAL FIBER/FSO COMMUNICATION SYSTEM USING ADVANCED MODULATIONS
    (Hawassa University, 2021-04-21) FISEHA ZELALEM
    Due to its lower attenuation and high bandwidth, current telecommunication infrastructure uses optical fibers for high data long haul transmission. Free space optics (FSO) technology is a good option for short-distance multi-gigabits per second or beyond data transmission. Nowadays, it has different application areas such as indoor, outdoor, underwater, and deep-space communications. A key area within this new generation is the combination of optical fiber and FSO network to provide high bandwidth for both long and short-distance services. The hybrid link uses coherent optical advanced modulation and dispersion compensation techniques to achieve the best performance with the existence of atmospheric turbulence effect and fiber limitations. Orthogonal frequency division multiplexing (OFDM) and dual-polarization quadrature phase-shift keying (DP-QPSK) are considered promising technologies to satisfy the demand for bandwidth expansion in broadband services. OFDM can overwhelm optical fiber limitations such as polarization mode dispersion (PMD) and chromatic dispersion (CD), whereas DP-QPSK provides good noise immunity. This thesis concentrates on designing, simulation, and performance analysis of 100Gbits/s data rate hybrid optical fiber/FSO systems using coherent optical OFDM and DP-QPSK modulation techniques. MATLAB software and OptiSystem simulation tool are used to design and simulate the hybrid system. To study the performance of the systems and the quality of the signals the bit error rate and the Q-factor are considered. As a result, for 100Gbits/s per channel with DP-QPSK based system, the link coverage is up to 468m in FSO and 202km by fiber cable; and up to 510m FSO link and 220km by fiber optics for CO-OFDM system. It is observed that the CO-OFDM system has high tolerance against linear signal distortion effects and sensitive to nonlinear effects which affects the system performance