【作者】 王里；

【导师】 娄淑琴； 黄卫平；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2010， 博士

【摘要】 随着视频流媒体等新业务的不断涌现,对网络带宽的需求以超摩尔定律的速度迅速增长,基于超大容量高速光传输和光交换的全光网络已经成为下一代通信骨干网的发展趋势。随着传输链路速率的提升,在高速、低成本、低功耗全光器件的研究上实现突破成为了推动全光网络研究进程的关键一环。近几年来,由于具有非线性强、体积小、易集成等一些独特的优势,半导体光放大器(SOA)作为全光信号处理的重要功能部件之一,成为光学领域和通信领域的研究热点。本论文在国家973项目“面向光路交换网络的光器件理论与关键技术研究”支持下,针对超高速率和超大容量全光网络对高速全光信号处理器件的应用需求,对SOA中的超快增益动态特性、超快相位动态特性和超快啁啾动态特性进行了深入的理论研究,获得的主要创新成果如下：1.提出了一个宽带SOA超快动力学模型,并采用已有实验文献报道进行了验证。与目前已有SOA超快模型相比,该模型积分容易收敛、不依赖于常数线宽增强因子和增益压缩因子,尤其适用于大信号分析和泵浦波长与探测波长间隔很大的宽带情形。在此理论模型的基础上,采用标准C++开发了一个面向对象的数值模拟软件库,首次在软件功能上将传统SOA、纵向激光增益钳制SOA和垂直激光增益钳制SOA的数值模拟过程统一起来。2.系统地研究了单个亚皮秒光脉冲激励下宽带情形SOA中的超快动态特性,首次发现了超快增益和相位动力学的波长依赖性。在1450-1650 nm的波长范围中,波长越短,载流子加热效应引起的增益变化越大、相位变化越小；波长越接近泵浦光波长,光谱烧孔效应引起的增益变化越大、相位变化越小；而双光子效应无明显波长依赖性。在长波段,增益恢复时间短且动态范围大、相位动态范围小,易于高速交叉增益调制应用；在短波段,相位恢复时间短且动态范围大、增益动态范围小,利于高速交叉相位调制应用。3.与皮秒光脉冲激励的情形不同,当考虑了光谱烧孔和双光子吸收效应的影响后,亚皮秒光脉冲激励下的SOA中的啁啾动力学过程包含中间的红移部分和两侧的蓝移部分,并呈现较强的波长依赖性。该结果表明,对于在皮秒光脉冲激励下基于瞬态交叉相位调制与失谐滤波器组合改善交叉增益调制码型效应的方案,在亚皮秒光脉冲激励的应用中将不再适用。4.提出了一种基于Mach-Zehnder干涉仪和体材料SOA中交叉增益调制的高速全光逻辑异或门。该方案通过采用带内直流光和较长的SOA改善了长载流子寿命引起的码型效应,可以实现直至Tb/s的工作速率。通过数值模拟验证和评估了基于该方案的250 Gb/s、500 Gb/s和1 Tb/s的全光异或逻辑门,所得异或结果的信号眼图张开度好且Q-factor大。5.首次提出采用两个不同带隙SOA的级联,选择合适的SOA带隙、注入电流和长度,可以有效改善高速交叉增益调制的码型效应。本方案具有结构简单和易于单片集成的优点。更多还原

【Abstract】 With streaming video and other new internet services emerging, the demand for network bandwidth increases rapidly at a rate beyond Moore’s Law. All-optical networks based on large-capacity and high-speed optical transmission and switching have become the trend of the backbone of the next generation communication networks. With the increase of the transmission-link speed which may be more than Tb/s, to make a breakthrough in the research of high-speed, low-cost and low-power all-optical devices becomes an important key to promote the research process of all-optical networks. In recent years, owing to their high nonlinearity, small volume, easy integration and other unique properties, semiconductor optical amplifiers (SOAs) as key functional elements in all-optical signal processing have been attracting huge attentions from the fields of optics and communications. Supported by the National 973 Program of "Research on the theory and key techniques of optical devices towards the all-optical switching networks", with the purpose of providing ultrahigh-speed all-optical signal processing devices for the all-optical networks, we deeply and theoretically study the ultrafast gain dynamics, ultrafast phase dynamics and ultrafast chirp dynamics in SOAs. The main contributions of this dissertation are listed as follows:1. Verified by the existing experimental literatures, a novel wideband model for describing the ultrafast dynamics and processes in SOAs is presented and realized. Compared with the current ultrafast dynamics models of SOAs, this model has several advantages:the integral in this model easily converging, obviating the approximations of the constant linewidth enhancement factor and the gain compression factors, and especially applicable to large-signal analysis and broadband case such as a wide interval between probe and pump wavelengths. In the frame of this theoretical model, based on object-oriented approach and the standard C++ language, a software library for numerically simulating the ultrafast dynamics in SOAs is developed. Through this software library, for the first time, the numerical simulation processes are unified for the conventional SOAs, SOAs gain-clamped by a longitudinal laser and SOAs gain-clamped by a vertical laser.2. The ultrafast dynamic properties in a SOA excited by a sub-picosecond optical pulse are systematicaly and theoretically studied in the wavelength range of 1450-1650 nm. For the first time, the wavelength dependence of the ultrafast gain and phase dynamics is discovered. The shorter the wavelength, the larger the gain change induced by carrier heating, and the smaller the phase change induced by carrier heating. The closer the wavelength to the pump wavelength, the larger the gain change induced by spectral-hole burning, and the smaller the phase change induced by spectral-hole burning. The effect of two-photon absorption is nearly independent of wavelength. Owing to the shorter gain recovery time, larger gain dynamic range and smaller phase dynamic range, in the band of longer wavelength, it is easy to realize high-speed applications based on cross-gain modulation. Owing to the shorter phase recovery time, larger phase dynamic range and smaller gain dynamic range, the band of shorter wavelength is beneficial to high-speed applications based on cross-phase modulation.3. Different from the situation in which a SOA is excited by a picosecond optical pulse, when considering the effects of spectral-hole burning and two-photon absorption, the chirp dynamic process in a SOA excited by a sub-picosecond optical pulse contains the middle part of red shift and the two side parts of blue shift. Moreover, the ultrafast chirp dynamics is obviously dependent on wavelength. It is shown that the proposed combination of transient cross-phase modulation and a detuned optical bandpass filter to effectively reduce the pattern-effect in cross-gain modulation in the situation of picosecond optical pulses is out of action in the situation of sub-picosecond optical pulses.4. An ultrahigh-speed all-optical XOR logic gate based on a Mach-Zehnder interferometer and cross-gain modulation in bulk SOAs is proposed, which uses continueous-wave light in the gain bandwidth and two long SOAs to reduce the pattern-effect inflicted by long carrier lifetime. Through numerical simulation, we evaluated this XOR logic gate operating at 250 Gb/s,500 Gb/s and 1 Tb/s, respectively. The simulation results show that the eye-diagrams of these XOR output signals are clearly open with high Q-factor.5. For the first time, two cascaded SOAs with different bandgaps are proposed and evaluated to reduce the pattern-effect in high-speed cross-gain modulation. Through appropriately arranging the two SOAs’bandgaps, injected currents and lengths, the pattern-effect in high-speed cross-gain modulation can be effectively reduced. This proposal has a simple structure and can be easily integrated into a single chip.更多还原