串联微环谐振器的光学特性

根据波导耦合方程,导出了串联微环谐振器的传输矩阵,并分析了环数、环间耦合系数以及损耗对串联微环谐振器输出特性的影响。数值模拟表明,串联微环谐振器具有光子带隙的特征。当环数增加时,通带内满足谐振条件的波长数增加;当环间耦合系数增加时,可使通带带宽加宽;通过适当选择环数和环间耦合系数,可以实现滤波和波分复用(WDM)的功能。选用脉冲宽度为50 ps的高斯型激光脉冲注入微环谐振器,发现当环间耦合系数较小时,出射脉冲相对于入射脉冲具有光学延迟的效果,并且随着环数的增加,延迟时间逐渐增大,而当环间耦合系数较大时,光学延迟效果不明显。     

基于硅基微环谐振器的光学导向逻辑器件

光学导向逻辑器件是采用光开关网络执行逻辑运算的典型应用,光学网络中每一个开关的状态由施加到该开关的电学布尔信号决定。网络中每一个光开关的操作都是独立于其他光开关的操作,并且操作运算结果以光速在网络中传播。因此,光学导向逻辑器件具有非常高的运行速度,且总延迟非常小。硅基微环谐振器由于其尺寸小、功耗低、与CMOS工艺兼容等特性成为构建光学导向逻辑器件的理想单元器件。基于硅基微环谐振器的光学导向逻辑器件很容易实现大规模集成和低成本制备,已经提出并实现的基于硅基微环谐振器的光学导向逻辑器件包括"或/或非"、"与/与非"、"异或/同或"、编码器、译码器和半加器等。回顾了本课题组基于硅基微环谐振器实现的光学导向逻辑器件的研究成果和该领域的最新发展。     

Optical Microring Resonators in Fluorine-Implanted Lithium Niobate for Electrooptical Switching and Filtering

We present a new approach for the fabrication of electrooptically tunable microring resonators in lithium niobate. Planar optical waveguides for vertical light confinement (Deltan o = 0.17) are produced by fluorine ion implantation. Optical microrings and bus waveguides are then formed by laser lithography masking and Ar⁺ plasma etching. Electrodes are optically isolated from the optical microrings by a polyvinyl alcohol buffer layer with a high dielectric constant (epsiv ~ 70 at 10 Hz) to improve electrooptic tuning. The microrings with a radius of 80 mu m exhibit optical resonances with a modulation depth of 11 dB, a free spectral range of 2 nm, and an electrooptical tunability of 10 pm/V.     

Dynamic Waveband Switching in WDM Mesh Networks Based on a Generic Auxiliary Graph Model

Waveband switching (WBS) is a promising technique to reduce the switching and transmission costs in the optical domain of a wavelength-division multiplexing (WDM) network. This paper considers the problem of provisioning dynamic traffic using WBS in a WDM mesh network. The network of interest is a homogeneous WBS network, where each node has the functionality of WBS. The problem is called the dynamic WBS problem, which involves searching waveband-routes or wavelength-routes for the dynamically arriving traffic requests. The objective is to minimize the total switching and transmission costs in the optical domain. To solve the dynamic WBS problem, an auxiliary graph model capturing the network state is proposed. Based on the auxiliary graph, two heuristic on-line WBS algorithms with different waveband grouping policies are proposed, namely the wavelength-first WBS algorithm based on the auxiliary graph (WFAUG) and the waveband-first WBS algorithm based on the auxiliary graph (BFAUG). Simulation results indicate that WBS is an attractive technique which reduces the overall switching and transmission costs by up to 30% in the network. The results also show that the WFAUG algorithm outperforms the BFAUG algorithm in terms of port savings and cost savings.     

Performances of a Fully Integrated All-Optical Pulse Reshaper Based on Cascaded Coupled Nonlinear Microring Resonators

We propose a simple way to design a fully integrated and passive all-optical pulse reshaper in the aim of reamplifying and reshaping (2R) regeneration of optical digital signals. The device could be achieved from a coupled microresonator structure with Kerr nonlinearity. By using time-domain simulation, we show that we can obtain a clear nonlinear power transfer that is capable of improving signal-to-noise ratio and reducing bit error rate for digital signals. The reshaping performances are estimated by calculating Q-factor enhancement. Since we take benefit from field enhancement at resonance, this integrated reshaper could be much smaller than other gates based on nonlinear fibers or waveguides.     

Group Delay Enhancement in Circular Arrays of Microring Resonators

Circular arrays of microring resonators are proposed for enhancing the group delay of slow-wave microring lattice structures. Large peak delay enhancements can be obtained and dynamically tuned by simply varying the loop coupling coefficient. It is also shown that maximally flat group delay responses can be achieved in these structures for potential application in compact dispersionless optical delay elements.     

Synthesis of Elliptic Optical Filters Using Mutually Coupled Microring Resonators

Integrated optical filters having elliptic transfer functions are proposed using two-dimensional arrays of synchronously tuned mutually coupled microring resonators. Analysis of microring filter topologies of the most general form is facilitated by the formulation of an energy-coupling matrix for the microring array. A method for synthesizing elliptic microring filter transfer functions having the prescribed transmission poles and zeros is also presented. The approach involves representing the microring filter by an equivalent electrical network of coupled LC oscillators and applying the coupling matrix technique developed for micro-wave filters to determine the coupling parameters. An example of a sixth-order elliptic function filter is presented to demonstrate the feasibility of using mutually coupled microring resonators to realize optical filters having finite transmission zeros in the transfer function     

MAC Protocol of a Next-Generation MAN Architecture Based on WDM and All-Optical Packet Switching

As media converge to the Internet, MANs will face new demands not only in terms of bandwidth, but also in terms of services. We describe a next generation MAN architecture that has been designed within Dutch project Flamingo. Based on all-optical packet switching, this architecture supports one-to-one, one-to-many and many-to-one communications in the optical domain. Specifically, we focus on the MAC layer of the network. We describe the access and fairness protocols and explain how the all-optical nature of the architecture affects the design of these protocols. We also discuss some performance results that have been obtained via simulation.     

All-Optical Label Extractor/Eraser for In-Band Labels and 160-Gb/s Payload Based on Microring Resonators

Photonic integration of an all-optical packet switch (AOPS) is a crucial issue since it leads to a great reduction of volume, power consumption, and costs. Recently, a 1 times 4 AOPS was successfully demonstrated by using an all-optical label extractor/eraser. The label extractor/eraser was implemented by means of fiber Bragg gratings and optical circulators that prevent the photonic integration of the AOPS. Here, we demonstrate a passive and asynchronous photonic integrated all-optical label extractor/eraser by using narrowband silicon-nitride add-drop ring-resonators. By exploiting the narrow bandwidth of the drop port and pass-through port error-free simultaneous separation/erasing of the in-band labels from the 160-Gb/s packet payload was demonstrated without noticeable pulse-shape distortions.     

Athermalizing and Trimming of Slotted Silicon Microring Resonators With UV-Sensitive PMMA Upper-Cladding

This letter experimentally demonstrates significant reduction in the resonance thermal sensitivity of the slotted silicon microring resonators by exploiting polymethyl methacrylate (PMMA) as upper-cladding. We investigate the resonance temperature dependence on the slot width with and without PMMA upper-cladding. The experimental results show that the temperature dependence is reduced from 91 pm/$^{circ}$ C for a regular microring resonator to 27 pm/ $^{circ}$C for the PMMA-clad slotted microring resonator. The ultraviolet (UV) sensitive PMMA upper-cladding also allows the resonance wavelengths of slotted microring resonators shift by 0.5 nm under UV light trimming. With the demonstrated schemes, each individual optical component can be athermalized and precisely registered to standard wavelengths for a future multiwavelength optically interconnected computing system-on-a-chip.      

基于WDM网络的多播动态选路算法研究

提出了一个改进的稀疏分光器配置约束下的改进算法。在稀疏分光器配置约束下,多播路由不再是图论中”树”的形状,多播路由可能存在逻辑圈。现有的多播路由算法没有考虑这个特点,改进对此算法作了一下改进,通过仿真证明改进算法提高了网络性能。     

传输矩阵法分析多环高阶谐振滤波器特性

与输入／输出波导耦合的环型谐振腔能形成结构简洁、性能良好、集成度高的信道滤波器。为实现通带内频率响应平坦度高、滚降时间快的滤波效果,采用多环结构形成的高阶滤波器。利用传输矩阵法推导了环与环问通过串联耦合和并联耦合两种方式形成的多环高阶谐振滤波器的传输甬数公式。对于并联耦合结构,通过优化直接影响下话路滤波特性的环与环间直波导的长度,实现了下话路光谱的对称性。对于串联结构,影响其特性的主要因素为环与环间的耦合系数．要实现最大平坦的通带特性,通过数值计算得出各个环间耦合系数必须从中间到两侧对称增加的特性。     

一种应用于时分交换IP OVER WDM网络的动态波长分配算法

提出了一种应用于时分交换IP OVER WDM网络的动态波长分配算法。该算法通过设置空闲波长信道,并将这些信道在不同时隙以跳波长方式动态分配给数据传输速率要求较高的业务,以尽量满足用户需求。讨论了该算法的原理,并对算法性能进行了分析。结果显示该算法能够有效地满足不同用户的业务需求,进一步提高信道波长利用率。     

一种应用于时分交换IP OVER WDM网络的动态波长分配算法

提出了一种应用于时分交换IP OVER WDM网络的动态波长分配算法。该算法通过设置空闲波长信道，并将这些信道在不同时隙以跳波长方式动态分配给数据传输速率要求较高的业务，以尽量满足用户需求。讨论了该算法的原理，并对算法性能进行了分析。结果显示该算法能够有效地满足不同用户的业务需求，进一步提高信道波长利用率。     

基于多天线扇区切换的动态时隙分配算法

高宽带网络电台为当前信息化战场提供及时精确的战场信息。文章基于高宽带电台设计的DTRA协议,提出一种基于多天线扇区切换的动态时隙分配算法,该算法根据网络节点业务需求调整当前时隙并进行动态分配。仿真结果表明,文章提出的方法能够有效提高时隙利用率,优于DTRA协议的时隙分配算法。     

一种信噪比指导信道均衡方式切换的算法

针对短波信道数据引导均衡算法(Data-Directed Equalization Algorithm,DDEA)及其判决反馈式DDEA(Decision Feed-back Equalizer DDEA,DFE-DDEA)算法在高低信噪比上误码性能互补的特点,在分析最大似然信噪比估计算法基础上,提出了采用实时信噪比估计以指导信道均衡方式、在DDEA与DFE-DDEA间动态切换的DS-DDEA(DynamicSwitching DDEA)算法,改善误码率整体性能。仿真算法验证了信噪比估计和DS-DDEA算法的可行性和有效性。     

基于GMPLS的动态分布式WDM网状网路由选择算法研究

研究了在基于GMPLS的WDM网络中，当节点不具备波长变换能力并且配备有限个光收发器对时，如何为到达的业务请求建立标记交换路径（LSP）的问题。提出一种以跳数和带宽碎片要求为权重，合理分配带宽资源的新算法。仿真结果表明，该算法在保证用户业务可靠性要求的同时，能够更有效地提高全网资源的利用率，并大大降低网络阻塞的可能性。     

有源光纤环形腔的频率滤波特性

本文首先从理论上通过简单的分析得以了有源光纤环形腔的输出谱密度函数公式,该式清楚地表明光纤环形腔的频率滤波特性。从该公式出发,详细分析了环形腔输入光纤宽和环形腔参数对输出光谱谱型和线宽的影响。最后,通过设计不同的环形腔的自由谱宽和不同线宽的激光器作为输出光源,对上述理论分析做了实验验证。理论和实验表明,由于环形腔的强度传递函数是多峰的响应函数,环形腔自由谱宽和输入激光线宽的大小直接影响到环形腔输出光频谱形状,即是单峰输出还是多峰输出,对于不同形状的光谱输出,输出激光的线宽受环形腔的参数影响也各不相同。     

基于GMPLS的动态分布式WDM网状网路由选择算法研究

研究了在基于GMPLS的WDM网络中,当节点不具备波长变换能力并且配备有限个光收发器对时,如何为到达的业务请求建立标记交换路径(LSP)的问题。提出一种以跳数和带宽碎片要求为权重,合理分配带宽资源的新算法。仿真结果表明,该算法在保证用户业务可靠性要求的同时,能够更有效地提高全网资源的利用率,并大大降低网络阻塞的可能性。     

备用路由下一种新的WDM动态路由波长分配算法

基于波长转换度的空闲波长图模型,提出了一种用于WDM光网络在备选路由下的动态RWA算法。路由选择采用K条最短路径算法进行,备选路由集中首选最佳路由时考虑链路的代价、跳数和每一个链路上不可用波长数。通过计算机模拟,分析这3个参数对网络的阻塞率的影响,结果表明本算法中所选定研究的3个参数中选定路由的不可用波长数对网络阻塞率的影响程度比通道的代价,跳数对网络的影响程度大,这个结论对算法中这3个参数数值的选取提供了依据,使算法能够依据实际网络情况动态选取参数,降低网络阻塞率。