【作者】 史培明；

【导师】 顾畹仪；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2011， 博士

【摘要】 由于结合了光纤通信高带宽、低损耗、抗电磁干扰和无线通信可移动、灵活接入的优点,ROF技术被认为是未来工作在毫米波段的宽带无线接入网的一种良好解决方案。近十几年来,ROF技术一直是国内外学者的热点研究课题。在ROF系统中,以合理的成本产生高质量的毫米波信号是一项关键技术。与传统的电学方法相比,光学方法是一种更好的选择。目前,人们提出的产生毫米波信号的光学方法主要有三种,光外差、频率上变换、外调制器的非线性调制。三种方法中,基于外调制器的非线性调制的方法对应的系统结构更为简单,成本更低,且可以产生高纯度、低相位噪声的毫米波信号。在该方法中,为了进一步降低系统的复杂度和成本,尤其是WDM-ROF系统,基于MZ调制器的非线性调制实现无光滤波高质量毫米波信号的产生是一种理想的方案。此外,色散是影响ROF系统传输性能的重要因素。一方面,色散致走离效应会导致码间干扰。另一方面,它会导致产生的毫米波信号的功率随传输距离呈周期性衰落。MZ集成调制器是由两个或两个以上的MZ子调制器构成的。与单个MZ调制器相比,通过设置MZ集成调制器的相关参数,可以在无光滤波的情况下实现高倍频因子的高质量毫米波信号的产生。为了更好的利用MZ集成调制器实现无光滤波的高质量毫米波信号产生,深入理解MZ集成调制器的调制特性非常重要。通过详细推导双电极MZ调制器主要调制技术的实现原理和简要介绍两种MZ集成调制器的结构和调制特性,为基于MZ集成调制器无光滤波产生高质量毫米波信号奠定了良好的理论基础。基于MZ调制器的非线性调制特性,利用MZ集成调制器,结合理论分析,本文提出了无光滤波的一种四倍频、两种六倍频和一种八倍频共四种产生高质量毫米波信号的新方案,并对所提方案进行了仿真和实验验证。同时,利用解析方法和数值仿真,对MZ调制器的偏置漂移、调制深度或调制电压、MZ子调制器间驱动信号的非理想相位差、MZ子调制器或MZ集成调制器的非理想消光比等关键因素对产生的光毫米波和毫米波信号质量的影响进行了深入分析,对产生的光毫米波信号的传输性能进行了一定的研究,对相应方案中的不同情况下光毫米波或毫米波信号质量进行了比较,并对已有的基于级联MZ集成调制器产生八倍频毫米波信号的方案进行了进一步研究。另外,利用解析方法对光纤光栅中的调制不稳定性的特性进行了深入分析和讨论。本文的主要研究工作和创新点如下：1)、提出了一种基于由两个MZ子调制器构成的MZ集成调制器无光滤波产生四倍频信号的新方案,并定义了衡量产生的光毫米波信号和毫米波信号质量的两个参量：光学边带抑制比—OSSR和射频杂散抑制比—RFSSR。仿真结果表明,在MZ子调制器消光比为30dB且无任何光滤波器和电滤波器的情况下,可以产生高质量的光毫米波信号和四倍频毫米波信号。基于推导得到的解析表达式,对影响产生光毫米波信号质量即OSSR的因素：偏置漂移、MZ子调制器的非理想消光比、MZ子调制器的调制深度进行了分析和讨论。实验中,我们得到的高质量的光毫米波信号和毫米波信号：OSSR超过了35dB,背靠背和经过40km光纤传输后对应的RFSRR分别为30.0dB和24.6dB。与背靠背情况下相比,经过40km光纤传输后,产生的四倍频毫米波信号的线宽未出现明显变化。2)、首次提出了一种基于由两个MZ子调制器构成的MZ集成调制器无光滤波产生六倍频信号的方案。仿真结果表明,在MZ子调制器的消光比为30dB且无任何光滤波器和电滤波器的情况下,可以产生高质量的光毫米波和毫米波信号。利用VPI仿真软件,深入分析和讨论了MZ集成调制器的非理想驱动电压、MZ子调制器间射频驱动信号的非理想相位差对OSSR和RFSSR的影响,并对产生的光毫米波信号的在光纤中的传输性能进行了研究。同时,对该方案中的两种情况对应的系统传输性能进行了比较。实验中,我们得到的高质量的光毫米波信号和毫米波信号：OSSR高于29dB,背靠背和经过40km传输后对应的RFSSR都超过了19dB。与背靠背情况下相比,经过40km光纤传输后,产生的六倍频毫米波信号的线宽未出现明显变化。3)、提出了一种基于由三个MZ子调制器构成的MZ集成调制器无光滤波产生六倍频信号的新方案。仿真结果表明,在MZ子调制器的消光比为30dB且无任何光滤波器和电滤波器的情况下,可以产生高质量的光毫米波和毫米波信号。基于推导得到的解析结果,深入研究了MZ集成调制器的非理想消光比和两MZ子调制器间驱动信号的非理想相位差对OSSR的影响,并对方案中两种情况下的OSSR进行了比较。实验中,我们得到的高质量的光毫米波信号和毫米波信号：OSSR约为31.0dB,背靠背和经过40km传输后对应的RFSSR都超过了20dB；与背靠背情况下相比,经过40km光纤传输后,产生的六倍频毫米波信号的线宽未出现明显变化。4)、提出了一种基于两个由两个MZ子调制器构成的MZ集成调制器级联产生八倍频毫米波信号的新方案。仿真结果表明,在MZ子调制器具有非理想消光且无任何光滤波器和电滤波器的情况下,该方案可以产生高质量的光毫米波信号和高纯度的毫米波信号。同时,对该方案中两种情况下的OSSR与RFSSR进行了比较。5)、首次利用解析方法对光纤光栅中的调制不稳定性进行了研究。对决定光纤光栅中调制不稳定性特性的色散方程进行了解析求解,在此基础上,深入分析和讨论了光纤光栅中调制不稳定性的特点。更多还原

【Abstract】 Due to the integration of the advantages of the extremely low loss, immune to electromagnetic interference and large available bandwidth of fiber communication and the mobile feature and flexible access of wireless communication, Radio over fiber (ROF) technology is regarded as a promising and attractive solution on the wireless access networks operating at the millimeter-wave (mm-wave) band. Over the past decade, ROF has been a research hotspot for the scholars both at home and abroad. In ROF system, the cost-effective and high quality generation of mm-wave is a key technology. Compared with the conventional electrical method, optical method is a preferable option for mm-wave generation.So far, three optical techniques have been proposed to implement the generation of mm-wave, namely, optical heterodyne, frequency up-conversion and nonlinear modulation of external optical modulator. Among these techniques, the last one has shown great potential for high purity and low phase noise mm-wave signal generation with low cost and simple configuration. For this technique, mm-wave generation without optical filter is an ideal scheme to further reduce the complexity and cost of system, especially for WDM-ROF system. In addition, fiber dispersion is an important influence factor for the transmission performance in ROF system. On one hand, fiber dispersion will lead to code interference because of walkoff effects. On the other hand, it also can lead to the periodical fading variation of the power of the generated mm-wave signal with transmision distance.Integrated MZM is composed of two or more sub-MZMs. Compared with single MZM, high multiplication factor and high quality mm-wave signal can be generated without optical filter if the parameters of integrated MZM are properly adjusted. In order to utilizing integrated MZM for quality mm-wave signal generation without optical filter, it is crucial to deeply understand the modulation chanracteristics of integrated MZM. The implementation principle of the main modulation techniques for the dual-electrodes MZM is derived in detail, and the structure and modulation characteristic of the two integrated MZMs are introduced in brief, which establishes the good theoretical foundation for mm-wave signal generation without optical filter based on the integrated MZMIn this dissertation, Utilizing the integrated Mach-zehnder modulator (MZM) and combining the theoretical analysis, four novel schemes for mm-wave signal generation without optical filter are proposed based on the nonlinear modulation of MZM, including one frequency quadrupling scheme and two frequency sextupling schemes and one frequency octupling scheme, and the feasibility of the proposed novel schemes are verified by simulation and experiment. At the same time, the influence of key factors such as bias drifting, modulation depth or modulation voltage, nonideal phase difference of RF driven signal applied to two sub-MZMs of the integrated MZM, imperfect extinction ratio of sub-MZM or integrated MZM on the quality of the generated optical mm-wave and mm-wave signal is thoroughly discussed and analyzed, and the transmission performance of the generated optical mm-wave distributed over fiber is also investigated and the performance of different cases of the related schemes is also compared. Furthermore, the pervious: octupling scheme is further investigated. In addition, the characteristics of modulation instability (MI) in a fiber grating are thoroughly discussed and analyzed with analytical method.The main research works and novelties of this dissertation are as follows:1). A novel frequency quadrupling scheme for mm-wave signal generation without optical filter based on an integrated MZM composed of two sub-MZMs is proposed, and two parameters, namely optical sidebands suppression ratio (OSSR) and radio frequency spurious suppression ratio (RFSSR) are defined to evaluate the quality of the generated optical mm-wave and mm-wave signal. The simulation results show high quality optical mm-wave and mm-wave signal can be generated without any optical and electrical filter when an integrated MZM composed of two sub-MZMs with extinction ratio of 30dB is utilized. Based on the analytical expression from the derivation, the influence of bias drifting, imperfect extinction ratio and modulation depth of sub-MZMs is discussed and analyzed. In experiment, high-quality optical mm-wave signal and mm-wave signal are obtained. The OSSR higher than 35dB is achieved. RFSSR with 30.0dB and 24.6dB is achieved for BTB and after transmission over 40km fiber, respectively. No obvious linewidth variation of the generated frequency quadrupling mm-wave signal is demonstrated after transmission over 40km of fiber.2). A frequency sextupling scheme for mm-wave signal generation without optical filter based on an integrated MZM composed of two sub-MZMs is firstly proposed, to our best knowledge. The simulation results show high quality optical mm-wave and mm-wave signal can be generated without any optical and electrical filter when an integrated MZM composed of two sub-MZMs with extinction ratio of 30dB is utilized. Utilizing VPI software, the influence of nonideal RF modulation voltage and nonideal phase difference of RF driven signal applied to sub-MZM of the integrated MZM is discussed and analyzed, and the performance of the generated optical mm-wave signal after transmission over fiber is investigated. Furthermore, the performance of two cases for the proposed scheme is also compared. In experiment, high-quality optical mm-wave signal and mm-wave signal are obtained. The OSSR higher than 29dB is achieved. RFSSR both exceeds 19 dB for BTB and after transmission over 40km fiber. No obvious linewidth variation of the generated frequency sextupling mm-wave signal is demonstrated after transmission over 40km fiber.3). Another frequency sextupling scheme for mm-wave signal generation without optical filter based on an integrated MZM composed of three sub-MZMs is proposed. The simulation results show high quality optical mm-wave and mm-wave signal can be generated without any optical or electrical filter when an integrated MZM composed of three sub-MZMs with extinction ratio of 30dB is utilized. Based on the analytical expression from the derivation, the influence of nonideal phase difference of RF driven signal applied to sub-MZM of the integrated MZM, imperfect extinction ratio of integrated MZM on OSSR is discussed and analyzed, and OSSR of two cases of the proposed scheme is also compared. In experiment, high-quality optical mm-wave signal and mm-wave signal are obtained. The OSSR about 31dB is achieved. RFSSR both exceeds 20dB for BTB and after transmission over 40km fiber. After transmission over 40km fiber, no obvious linewidth variation of the generated frequency sextupling mm-wave signal is demonstrated.4). A novel frequency octupling scheme based on two cascaded integrated MZM composed of two sub-MZMs is proposed. The simulation results show high quality optical mm-wave and mm-wave signal can be generated without any optical or electrical filter when an integrated MZM composed sub-MZMs with imperfect extinction ratio is utilized. Moreover, OSSR and RFSSR of two cases are also compared based on simulation results.5). MI in a fiber grating is investigated firstly by analytical method, to best our knowledge. The dispersion relation that determines the characteristics of MI in a fiber grating is solved exactly, and the characteristics of MI in a fiber grating is thoroughly discussed and analyzed based on the analytical solution.更多还原