| Recently, during the integration of telecommunications networks, cable TV networks and Internet networks (tri-networks integration), and the development of the bandwidth-hungry applications such as Hi-Vision/Ultra High Definition TV, video conference and video games, the IP-based, broadband and wireless optical communication network has attracted more and more research interest. Moreover, due to the flexible modulation format, high channel and spectral efficiency, and robust against fiber dispersion effects in optical fiber channels and wireless multipath fading in wireless channels, orthogonal frequency division multiplexing (OFDM) has attracted more and more attention from global telecommunication operators, and been widely used in Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), Wireless Local Access Network (WLAN, IEEE802.11), and the4th Mobile Communication System (4G). Furthemore, radio over fiber techniques have been regarded as a promising solution to meet the explosive demand of bandwidth and the large number of broadband subscribers. Therefore, it is very essential to research the application of OFDM techniques in the next generation optical access network and fiber-wireless intergration network, there are important theoretical and practical values.After systematically analyzing the principle of OFDM technique and the transmission problem of OFDM signal in the fiber and wireless hybrid channel, this thesis presents the simulation and experimentation for validation, and realizes the implementation of OFDM technique in the next generation optical access network and fiber-wireless intergration network. The major achievements of this thesis are summarized as follows:(1) By using the orthogonal frequency division multiple access (OFDMA) and subcarrier modulation (SCM) technologies, the novel time-divison multiplexing passive optical network (TDM-PON), wavelength-division multiplexing PON (WDM-PON) and hybrid WDM and TDM PON (HPON) architectures which support efficiently and flexibly local access network (LAN) emulation among optical network units (ONUs) are proposed in this thesis. Experimental and simulation results show that by optimizing RF carrier frequency, NRZ-to-OFDM power ratio, the frequency space and number of OFDM subcarriers, the impact of intermixing nosie and fiber dispersion on the LAN and PON traffic could be efficiently reduced. The proposed LAN emulation schemes have several advantages. Firstly, multiple LAN traffics can be concurrently transmitted in the same time slot due to the use of OFDMA protocol. Secondly, the bandwidth of the LAN traffic in each ONU can be flexibly adjusted by allocating OFDM subcarriers and time slots. Thirdly, by using the RF subcarrier multiplexed transmission, the LAN traffic could not occupy the bandwidth of the upstream and downstream traffics. These schemes could provide technical support for the development of the efficient virtual private network in the next generation passive optical network system.(2) By analyzing and discussing the impact of fiber dispersion, wireless multi-path fading, and channel nonlinearity on the high-order modulation format OFDM signal, the optimal DSP algorithms including time synchronization, frequency and phase recovery and channel estimation and equalization are designed to realize the low cost and high spectral efficiency WiFi signal over fiber system for in-building network. The performance of different modulation order OFDM signal is analyzed using directly modulated VCSELs at850nm for the multi-mode fiber (MMF) transmission, and at1310nm and1550nm for the bend insensitive fiber (BIF) transmission. Experimental results show that for the MMF case, a spectral efficiency of1.44bits/s/Hz with a net bit rate of300.144Mb/s could be achieved, and a spectral efficiency of4.31bits/s/Hz corresponding to a net bit rate of900.432Mb/s is obtained for the BIF case. Moreover, this thesis has presented a spectral efficient and WDM-PON compatible MIMO-OFDM access system by combining optical polarization division multiplexing (PDM) and wireless multiple input multiple output (MIMO) spatial multiplexing techniques. And a training-based zero forcing (ZF) algorithm is digitally developed to estimate the polarization multiplexed MIMO transmission channel. A797Mb/s net data rate QPSK-OFDM signal and a1.59Gb/s net data rate16QAM-OFDM signal at5.65GHz RF carrier frequency are transmitted over3m and1m air distance with22.8km single mode fiber respectively.(3) In this thesis, we have built the high speed W-band (75-110GHz) OFDM signals over fiber test bed. By using optical I/Q modulator, optical comb generator, and optical heterodyne beating based W-band signal generator, a spectral efficiency of2.808bits/s/Hz with a net bit rate of42.13Gb/s16QAM-OFDM signal at86GHz RF carrier frequency is transmitted over fiber and wireless hybrid channel. The theoretical derivation and experimental analysis show that the phase noise of lasers, the high PAPR of transmitted OFDM signal and channel nonlinearity have significant impact on the system performance. By using efficient phase noise compensation alogorithm and improved channel estimation algorithm, the42.13Gbit/s16QAM-OFDM signals at86GHz are successfully transmitted over0.6m air distance. Moreover, to resolve the high system requirement about linear amplifier and modulator due to the high PARP of OFDM signal, and avoid the deterioration influence of the laser phase noise, a constant envelop OFDM W-band wireless signal over fiber system based on optical modulator has been proposed in this thesis. The analysis shows that the phase noises of lasers and LO oscillator appear as additional terms to the received signal, resulting in significant complexity reduction. In our experiment,8Gb/s16QAM-OFDM signal is successfully transmitted over2.3m air distance and22.8km single mode fiber. These research results provide technical support for the future fiber-wireless system which can obtain high speed, high bandwidth and large transmission distance.
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