【作者】 邓磊；

【导师】 刘德明；

【作者基本信息】 华中科技大学 ， 电子科学与技术， 2012， 博士

【摘要】 随着电信网、广播电视网和互联网的融合,以及一些高带宽业务如高清电视、网络会议和视频游戏的开展与普及,IP化、宽带化和无线化已经成为下一代光通信网的研究热点。而正交频分复用(OFDM)技术以其灵活的调制方式、更高的信道及频谱利用率和更好的色散及多径衰落容忍度,引起了全球各大电信运营商越来越多的关注,已经被广泛应用在数字音频广播(DAB)、数字视频广播(DVB)、IEEE802.11无线局域网和下一代移动通信系统(4G)中。为了满足未来接入网高速率、大带宽和宽覆盖的需求,发展新型的下一代光接入网技术和光纤无线融合技术已势在必行,因此,研究OFDM技术在下一代光接入网络和光纤无线融合网络中的应用具有很高的理论和实用价值。本论文在系统地分析了OFDM基本原理及OFDM信号在光纤与无线信道中传输所面临问题的基础上,通过仿真和实验研究,实现了OFDM技术在下一代无源光网络和光纤与无线融合网络中的应用,并取得了若干创新成果。具体研究内容包括：(1)通过理论研究和实验分析,结合正交频分多址(OFDMA)技术的优势,提出了支持光网络单元(ONU)之间高效互连互通的新型时分复用无源光网络(TDM-PON)、波分复用无源光网络(WDM-PON)以及时分波分混合无源光网络(HPON)系统。仿真和实验结果表明在这些基于OFDMA技术的ONU互通系统中通过优化OFDM信号和PON业务信号的功率比、OFDM信号频率间隔及子载波个数,可以有效减小噪声及色散对混传业务性能的影响,使系统具备动态灵活的互通业务带宽分配机制、互通业务完全不占用PON业务带宽及支持多个互通业务并发等优势,为下一代无源光网络中高效虚拟局域网(VPN)研究提供了技术支持。(2)实验分析和探讨了光纤与无线融合系统中调制器啁啾及信道色散和非线性对高阶调制格式OFDM信号传输性能的影响,通过优化设计OFDM接收端时钟同步、频率相位估计以及信道估计和均衡算法,实现了基于低成本VCSEL的光载无线系统内5.5GHz载频300.144Mb/s QPSK-OFDM信号在100m多模光纤和900.432Mb/s64QAM-OFDM信号在1km弯曲不敏感光纤中的传输。此外,还创新地提出融合了偏振模复用(PDM)技术和无线多入多出(MIMO)技术的高频谱利用率、高速率光载无线系统,设计了基于Zero Forcing(ZF)的信道估计算法以补偿光纤中偏振的旋转及无线中信号的多径衰落,实现了2×2MIMO光载无线系统内5.65GHz载频1.59Gb/s16QAM-OFDM信号在22.8km单模光纤和1m无线距离中的传输。(3)搭建了光载高速W-band (75-110GHz) OFDM无线信号的测试平台,创新地使用光IQ调制器、光频梳产生器及光外差拍频的方式产生了速率为42.13Gb/s、频谱利用率为2.808bits/s/Hz的86GHz载频16QAM-OFDM信号。理论推导和实验分析了激光器相位噪声、OFDM信号峰均比及光纤非线性效应对W-band无线传输性能的影响,提出了高效的激光器、频率源相位噪声补偿算法及基于OFDM信元频域平均法(ISFA)和数字锁相环(DPLL)的增强型信道估计和均衡算法,成功将42.13Gb/s86GHz载频16QAM-OFDM信号传输了0.6m无线距离。此外,设计了基于光相位调制器的恒包络OFDM传输系统,极大地减弱了系统对高线性放大器和调制器的需求。理论推导和实验结果证明,在此系统中激光器和频率源的相位噪声对信号只是一个加性分量,通过滤波器极易滤除,极大地降低了系统复杂度。系统实验成功地实现了8Gb/s81.5GHz载频16QAM-OFDM信号在22.8km单模光纤和2.3m无线距离中的传输。这些研究成果为下一代高速无线光通信系统的发展提供了技术支持。更多还原

【Abstract】 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.更多还原