【作者】 杨波；

【导师】 金晓峰；

【作者基本信息】 浙江大学 ， 物理电子学， 2013， 博士

【摘要】 微波振荡器作为微波信号源、高速通信参考时钟信号以及信号检测的频率标准,是通信系统、导航、雷达、测试仪器、电子对抗等射频应用领域的关键器件。光电振荡器(optoelectronic oscillator,OEO)采用光电反馈环路与光子储能的物理机制,将激光能量转换为微波信号能量,摆脱了传统微波振荡器随频率升高相位噪声显著升高的限制。OEO由于可以取得很低的相位噪声特性,在未来涉及微波/毫米波系统的许多重要领域具有广阔的应用前景。深入开展新型光电振荡器的相关理论与关键技术的研究还具有重要的科学意义与理论价值。本文对新型光电振荡器技术进行了深入研究。首先研究了OEO的工作原理,提出了OEO经典理论模型的一些修正。在此基础上,针对高频毫米波信号的产生和宽带可调谐OEO的实现,提出了一些创新的结构方案与关键技术,并进行了相关系统结构的实验验证。最后,结合未来宽带泛在接入网络中的光载射频传输(RoF)系统,研究实现了一种基于OEO的矢量信号上变频技术；并设计了一种适合于未来宽带泛在接入的毫米波RoF接入方案,进行了实验验证。论文的主要创新点和学术贡献如下：1.研究了OEO的工作原理,通过分析OEO经典理论模型(Yao-Maleki Model),提出了对Yao-Maleki理论模型的修正,通过实验验证了微波放大器非线性会限制OEO振荡功率,频率相关的闪烁噪声会提高OEO近载波噪声的观点。2.利用马赫增德尔调制器(MZM)的非线性实现了高频毫米波信号的产生。首先提出了基于双电极马赫增德尔调制器(DEMZM)来实现OEO二倍频信号输出,具有结构简单、工作稳定、倍频信号质量高等优点。为了提高倍频次数,提出一种基于双平行马赫增德尔调制器(DPMZM)来实现OEO六倍频信号输出的方法,通过仿真证实了方案的可行性。最后,我们还实现了一种利用有理数谐波锁模光纤激光器产生四倍频60GHz信号的方案,可以提高外调制方法的倍频效率。3.在研究OEO频率调谐机理的基础上,提出了多种OEO宽带调谐的系统结构方案,丰富和完善了OEO灵活调谐的物理机制。论文首先提出了一种利用受激布里渊散射来实现宽带可调谐OEO的方法,并且通过载波相移双边带调制的方式,同时实现了OEO频率可调谐和倍频输出功能,其中系统固有的布里渊噪声限制了OEO的相位噪声性能。在此基础上,提出另一种基于窄带相移光纤光栅滤波和调节激光波长的方案。在单边带调制器的协助下,带有窄带透射峰的相移光纤光栅等效为一个高Q滤波器来选择振荡频率。通过调节激光器波长,实现了x波段的宽带可调谐输出。该方法具有结构简单、调节速度快等优点,并有可能实现几十GHz的频率调节范围。为了消除使用昂贵的可调谐激光器,论文提出了第三种方案。通过构建一个色散引起的复合腔微波光子滤波器,基于它来实现一种电压控制的、调谐范围达到数GHz的OEO。该方案只需要一个固定频率的激光器、具有电气友好的特性,其短环结构也适合光子集成。4.论文提出并实现了一种基于OEO来实现RoF系统中矢量信号上变频的方案。该方案不需要任何的电混频器和外部本振信号,避免了传统RoF系统中的两级调制过程；通过调节DPMZM的直流偏置点还可以轻易对RoF系统中色散引起的功率衰落进行预补偿。该方案结合了低噪声信号的产生和矢量信号的调制,拓展了OEO的应用。论文最后,提出了一个简单、有效的毫米波RoF接入方案,融合了毫米波信号产生,基站简化,抗色散性能、双向链路设计等关键技术,进行了实验验证。更多还原

【Abstract】 Microwave oscillators are widely used as microwave signal source, clocks in high-speed communication and frequency standards in signal detection. Microwave oscillators are critical components in radio frequency applications such as communication system, navigation, radar, instruments, and electronic countermeasures. Based on electro-optical feedback technique and photonic energy storage mechanism, optoelectronic oscillators (OEOs) convert light energy to microwave signal and overcome the limitation of traditional microwave oscillator in phase noise performance. With the ability of generating low phase noise high frequency signals in both electrical and optical domain, the OEOs have wide applications in many important areas, especially for the microwave/millimeter-wave systems.The study in related theory and key technology of the novel OEO is of scientific significance and great theoretical value.In this dissertation, the novel OEO and its application in RoF are studied. At first, the operation principle of OEO is analyzed and several modifications of the classical theoretical model are proposed. Then, the generation of mm-wave signals and realization of wideband frequency-tunable OEOs are studied. Several novel schemes and key technologies are proposed and validated by experiments. At last, photonic microwave up-conversion of vector signals based on a single optoelectronic oscillator for radio over fiber (RoF) system is proposed and demonstrated; a mm-wave RoF system scheme is proposed and demonstrated for the broadband and ubiquitous access network in the near future. The major innovations and contributions are as follows:1. The operation principle of OEO is analyzed. After analyzing the classical theoretical model of OEO, two main modifications to the model are proposed and demonstrated. The first one is that the oscillation power of OEO may be limited by the gain saturation of microwave amplifier. The second one is that the close-in phase noise of OEO will be increased by the frequency dependent flicker noise. 2. By using the nonlinearity of the Mach-Zehnder Modulator (MZM), generation of mm-wave signal is achieved. At first, a frequency-doubling OEO based on a dual electrode MZM (DEMZM) is proposed and demonstrated. The approach features high stability, simple structure and high signal quality. To further increase the frequency multiply times, a frequency-sextupling OEO based on a DPMZM is proposed and validated by simulation. At last, photonic generation of60GHz mm-wave by frequency quadrupling based on a mode-locking SOA fiber ring laser with a low modulation depth MZM is proposed, the frequency-multiplying efficiency can be improved.3. Based on the study on frequency-tunable mechanism of OEO, several novel wideband frequency-tunable OEOs are proposed and the flexible tuning mechanisms of the OEO are improved. At first, a frequency-tunable OEO based on stimulated Brillouin scattering (SBS) and carrier phase-shifted double sideband (CPS-DSB) modulation is proposed and demonstrated. The scheme achieves frequency-doubling and frequency tunability simultaneously for an OEO. However, the phase noise performance of OEO is limited by the Brillouin noise. Therefore, another wideband frequency-tunable OEO based on a narrowband phase-shifted FBG and wavelength tuning of laser is proposed. With assistance of an optical single sideband modulator, the PSFBG with a narrow transmission peak acts like an equivalent high-Q microwave filter to select the oscillation frequency. Frequency tunability of the OEO can be simply realized by tuning the wavelength of a laser source. An X band optoelectronic oscillating signal with frequency tunable at wide range from8.4to11.8GHz is generated. The approach features simple structure, high tuning speed and may realize a tunable range of dozens of GHz. To eliminate the expensive tunable laser, the third scheme is proposed. Based on a dispersion-induced microwave photonic filter (MPF), a GHz tunable range and voltage-controlled OEO is achieved. In this proposal, only a wavelength-fixed laser is required and the frequency tunability is realized by an electricity-friendly method. Besides, due to its short loop structure, it may find potential to integrate the discrete components of the proposed OEO into a chip.4. Photonic microwave up-conversion of vector signals based on a single optoelectronic oscillator with dispersion compensation for RoF system is proposed and demonstrated. The OEO incorporating DPMZM simultaneously works as a high-quality local oscillator (LO) and a broadband mixer to directly frequency up-converts vector signals. The common two-stage modulation in RoF system is avoided. Besides, the dispersion-induced power fading for up-conversion signal can be compensated by properly setting one DC bias of the DPMZM. The proposed approach combines the function of low phase noise microwave generation and vector signal modulation, develops the application of OEO. In the end, a simple and effective bidirectional mm-wave RoF system scenario for access network is proposed and demonstrated, involving the key technologies such as mm-wave generation, base station simplify, dispersion compensation, bidirectional transmission and so on.更多还原