48 resultados para SOA


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Broad-band semiconductor optical amplifiers (SOAs) with different thicknesses and thin bulk tensile-strained active layers were fabricated and studied. Amplified spontaneous emission (ASE) spectra and gain spectra of SOAs were measured and analyzed at different CW biases. A maximal 3 dB ASE bandwidth of 136 nm ranging from 1480 to 1616 nm, and a 3 dB optical amplifier gain bandwidth of about 90 nm ranging from 1510 to 1600 nm, were obtained for the very thin bulk active SOA. Other SOAs characteristics such as saturation output power and polarization sensitivity were measured and compared. (c) 2006 Elsevier B.V. All rights reserved.

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We have demonstrated an electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA) monolithically integrated with novel dual-waveguide spot-size converters (SSCs) at the input and output ports for low-loss coupling to planar light-guide circuit silica waveguide or cleaved single-mode optical fiber. The device is fabricated by means of selective-area MOVPE growth (SAG), quantum well intermixing (QWI) and asymmetric twin waveguide (ATG) technologies with only three steps low-pressure MOVPE growth. For the device structure, in SOA/EAM section, double ridge structure was employed to reduce the EAM capacitances and enable high bit-rate operation. In the SSC sections, buried ridge stripe (BRS) were incorporated. Such a combination of ridge, ATG and BRS structure is reported for the first time in which it can take advantage of both easy processing of ridge structure and the excellent mode characteristic of BRS. At the wavelength range of 1550-1600 nm, lossless operation with extinction ratios of 25 dB DC and more than 10 GHz 3-dB bandwidth is successfully achieved. The beam divergence angles of the input and output ports of the device are as small as 8.0 degrees x 12.6 degrees, resulting in 3.0 dB coupling loss with cleaved single-mode optical fiber. (c) 2005 Elsevier B.V. All rights reserved.

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A novel semiconductor optical amplifier (SOA) optical gate with a graded strained bulk-like active structure is proposed. A fiber-to-fiber gain of 10 dB when the coupling loss reaches 7 dB/factet and a polarization insensitivity of less than 0.9 dB for multiwavelength and different power input signals over the whole operation current are obtained. Moreover, for our SOA optical gate, a no-loss current of 50 to 70 mA and an extinction ratio of more than 50 dB are realized when the injection current is more than no-loss current, and the maximum extinction ratio reaches 71 dB, which is critical for crosstalk suppression. (C) 2003 society of Photo-Optical Instrumentation Engineers.

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The measurement and analysis of the microwave frequency response of semiconductor optical amplifiers (SOAs) are proposed in this paper. The response is measured using a vector network analyzer. Then with the direct-subtracting method, which is based on the definition of scattering parameters of optoelectronic devices, the responses of both the optical signal source and the photodetector are eliminated, and the response of only the SOA is extracted. Some characteristics of the responses can be observed: the responses are quasi-highpass; the gain increases with the bias current; and the response becomes more gradient while the bias current is increasing. The multisectional model of an SOA is then used to analyze the response theoretically. By deducing from the carrier rate equation of one section under the steady state and the small-signal state, the expression of the frequency response is obtained. Then by iterating the expression, the response of the whole SOA is simulated. The simulated results are in good agreement with the measured on the three main characteristics, which are also explained by the deduced results. This proves the validity of the theoretical analysis.

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We have demonstrated an electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA) monolithically integrated with novel dual-waveguide spot-size converters (SSCs) at the input and output ports for low-loss coupling to planar light-guide circuit silica waveguide or cleaved single-mode optical fiber. The device is fabricated by means of selective-area MOVPE growth (SAG), quantum well intermixing (QWI) and asymmetric twin waveguide (ATG) technologies with only three steps low-pressure MOVPE growth. For the device structure, in SOA/EAM section, double ridge structure was employed to reduce the EAM capacitances and enable high bit-rate operation. In the SSC sections, buried ridge stripe (BRS) were incorporated. Such a combination of ridge, ATG and BRS structure is reported for the first time in which it can take advantage of both easy processing of ridge structure and the excellent mode characteristic of BRS. At the wavelength range of 1550-1600 nm, lossless operation with extinction ratios of 25 dB DC and more than 10 GHz 3-dB bandwidth is successfully achieved. The beam divergence angles of the input and output ports of the device are as small as 8.0 degrees x 12.6 degrees, resulting in 3.0 dB coupling loss with cleaved single-mode optical fiber. (c) 2005 Elsevier B.V. All rights reserved.

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网络技术的快速发展和多变的业务需求使得软件功能日益复杂、规模日益庞大。面向服务架构作为一种新的计算范型,利用服务作为基本的构造单元,支持异构环境下分布式应用的快速、低成本开发。但是现有的面向服务架构实现方案在服务动态部署、动态生命周期管理,以及模块化方面均存在不足。OSGi(Open Service Gateway Initiative)提供了一种面向服务、基于组件的软件框架,易于构建模块化、动态可扩展的软件系统,在服务动态部署、生命周期管理,以及模块化方面具有优势。 论文首先分析了面向服务架构和OSGi技术的特点,以及相互之间的互补因素,在此基础上建立了一个服务协作总线概念架构,支持服务的动态部署、动态生命周期管理和透明协作。在该概念架构的基础上,设计了一种服务描述模型,以此为基础实现透明的OSGi服务发布与发现;扩展了OSGi服务部署和访问机制,实现分布透明的OSGi服务访问;通过声明式远程服务组件模型,实现了服务动态生命周期管理。在这些基础上,论文给出了服务协作总线系统OnceSCB的设计与实现。并通过应用案例和实验对OnceSCB的功能和非功能方面进行了评估。该服务协作总线实现远程服务的透明化访问以及远程服务与本地OSGi服务统一管理,提供透明的服务协作,形成一个基于服务协作的动态服务计算生态环境,为服务计算环境下服务开发、部署、管理提供支持。

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面向服务的计算(Service Oriented Computing,SOC)与面向服务的体系结构(Service Oriented Architecture,SOA)是分布式系统和软件集成技术领域中的一种新型的计算范型和体系结构。Web服务作为一种自治、开放以及平台无关的网络化构件,可使分布式应用具有更好的可重用性、灵活性和可扩展性,为Internet开放网络环境下的资源共享与业务集成提供了新的解决方案。然而由于Web服务的分布性以及异构、动态和不断演化的特点,使得服务之间的协作变得非常复杂,如何保证服务之间协作的正确性和可靠性便成为应用SOA架构的关键问题。适配技术为解决这一问题提供了可行的解决方案,服务适配使得原本无法正确交互的服务在服务适配器的介入下正确地完成协同工作,从而提高了服务组件的可重用性,实现了复杂系统的高效开发,保证了协作系统的可扩展性和健壮性。因此,服务适配机制的研究对面向服务计算技术的发展以及面向服务架构的成功应用与实施有着重要的意义。 本文在分析服务适配相关工作的基础之上,重点围绕服务协作中的分布式适配结构、适配器流程的自动生成方法,以及适配器的动态演化机制等几个方面的理论基础和关键技术展开研究工作,并建立了支持分布式适配的服务协作支撑框架和原型系统,对上述方法进行验证。本文主要的研究内容和贡献如下: 首先,本文提出了一种自顶向下地实现服务协作中分布式适配的方法。以全局服务协作流程为出发点,基于角色进行投影得到各个参与者对应的抽象服务接口,并以此为依据,为服务组件生成独立的适配器,实现分布式的服务适配结构,从而更加满足开放网络环境对于高效、灵活的服务协作机制的需求。本文深入探究了分布式适配模型的构造方法,定义了模型中各个层次的组成元素,重点给出了失败等价(Failure Equivalent)行为语义保持的投影规则,以保证全局协作流程与生成的抽象服务接口的等价性。 其次,围绕适配器流程的自动生成方法展开研究,现有方法对适配器流程的正确性进行分析时,只能给出确定的“是”或者“否”的结果,而并没有更深入地分析服务行为中无法适配的程度,从而无法对服务交互中的内在关系进行更深入的揭示。本文引入了可适配度的概念,以此来分析服务组件与协作需求的差异性,并给出了基于交互路径的方法来计算无法适配的节点及对应的模式。这样一方面可以依据可适配度来选择合适的服务进行协作,从而降低服务协作应用的开发成本,另一方面,开发人员还可以利用无法适配的相关信息,对服务实现进行有效地修改,这对于服务流程的管理和改进等方面都有着重要的作用。此外,与现有适配器自动生成方法相比,本文所给出的整体构造,一次性检查的方法,有效地降低了自动构造算法的复杂度。 再次,在面向服务的计算与面向服务的软件架构中,服务组件具有动态和不断演化的特性,现有的适配机制只是静态地分析了适配器的结构和相关属性,但是缺乏对适配器响应动态变化的可适应能力的研究。本文研究了适配器流程定义的自动更新以及适配器实例的动态调整方法,从而使适配器具有可重配置以及动态调整的能力,保证了基于适配的服务协作系统的灵活性和动态可适应性。 最后,在上述研究的基础之上,设计与实现了一个原型系统,包含了流程建模,协作管理以及协作运行三大模块,用于实现服务协作中的分布式适配方法。同时,针对每个核心组件,介绍了其功能模块的设计与实现,并基于实例说明了适配器的应用开发过程。

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在开放的互联网环境中,面向服务的计算(Service-Oriented Computing, SOC)和面向服务的体系架构(Service-Oriented Architecture, SOA)使得信息资源和软件系统的主要形态发生了巨大变化,并引领着互联网计算技术和软件系统新的发展方向。服务是SOC和SOA的核心思想,服务的平台独立、高可重用和松散耦合等特性使之成为复杂分布式应用可行的解决方案。Web服务的出现和发展为实施与部署SOC和SOA提供了最佳支撑技术。目前web服务发现机制在服务描述的全面性和服务匹配方法的有效性方面存在不足之处,难以保证服务发现的性能。特别是在服务数量剧增的情况下,用户亟需一种自动快速而准确的服务发现机制。语义web技术不仅为web的表示内容提供了一种语义标识方法,推动了web内容的自动化和智能化搜索,也为web服务的描述提供了增加语义层次内容的有效方法,两者的结合形成了一个新的研究领域——语义web服务。该领域通过借鉴语义web的相关技术来增加web服务的语义描述,进而为web服务的发现、组合、调用和监控等环节提供语义层次的支持,增强web服务的自动化和智能化水平。 本文的研究目的就是利用语义web的思想,基于SOC和SOA的理念以及现有的web服务发现机制对web服务信息进行语义描述、组织,探索语义web服务匹配与发现的关键问题,提出有效的解决方案。本文的研究工作和贡献主要在以下四个方面: 1. 针对语义近似度的度量和计算问题基于OWL(Web Ontology Language)提出了一个语义近似度计算SSM模型,该模型中所有概念及概念之间的关系、所有的概念属性及属性之间的关系都被抽象定义并建模,根据概念、属性及其语义关系模型,构建了基于概念关系的拓扑近似度计算函数和属性近似度计算函数,从而进一步构建语义近似度计算函数。该语义近似度计算函数以代表OWL本体概念上下级关系和等价关系的树状结构为基础,利用概念间的拓扑关系和属性关系进行语义近似度的度量和计算。语义近似度函数的返回值为一个介于0与1之间的数值,代表函数的两个输入概念之间的语义近似度值。 2. 提出了一个基于概念语义近似度的以OWL-S为顶层本体的web服务语义匹配PSM模型。该模型将服务的匹配项分为服务能力、服务质量、服务名称和服务参数四个部分。基于该模型,提出了相应的PSM服务匹配算法。PSM算法能够对服务内部的服务流程及流程的组合进行与服务请求的语义匹配,并且避免了服务流程中互斥接口参数参与匹配。而且PSM匹配算法实现了服务接口的单射匹配,进一步提高服务发现的性能。在服务质量匹配计算上,提出了服务质量匹配模型PSM-QoS,为服务的QoS匹配建立了计算基础。PSM算法使用语义近似度计算函数度量和计算服务属性概念的语义近似度值,从而能够返回细粒度的服务匹配度值。 3. 在语义服务匹配PSM模型的基础上提出一种语义web服务发现架构系统PSM-SD模型。该模型将OWL-S语义元素引入UDDI服务描述,从而在UDDI中保存语义信息。通过PSM算法提高web服务匹配性能,并通过数据映射机制保证模型对于当前的服务发现标准UDDI基础架构的兼容以及UDDI标准操作接口的透明性。模型使用本体概念的索引机制提高服务发现的效率。在建立和维护索引的过程或服务的匹配过程中,模型使用近似概念搜寻算法进一步提高本体概念搜寻和服务匹配的效率。 4. 设计并开发了基于语义web服务发现架构模型的原型系统。该系统将语义近似度计算模型、语义web服务匹配模型和语义web服务发现架构模型进行软件实现。本文在该原型系统平台上对语义web服务发现的方法进行了实验,验证了方法的有效性。

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卫星组网仿真是对各种卫星组网方案进行性能分析、效能评估以及优化设计的有效途径。限于单机负载及计算能力,卫星组网仿真采用分布式交互仿真形式。作为仿真的基本依据,想定编辑生成与想定发布是仿真首先需要解决的问题。此外,想定推演过程也应对仿真场景进行展示以方便观察仿真当前状态。如何构建满足需求的卫星组网仿真想定系统是本文研究目的之一。 围绕卫星组网仿真想定系统的功能需求,首先进行了需求分析与功能定义,接着对所涉及难点包括多任务多粒度组网仿真想定的灵活配置、细粒度组网仿真内存使用优化以及想定数据实时发布等的技术途径进行了比较与分析。在确定所选用技术基础上,设计出想定系统的总体结构框架。最后结合该框架对系统实现进行了详细的说明,并对内存优化问题进行了仿真实验。 在想定系统实现基础上,进一步分析了当前高层体系结构HLA标准在分布式式交互仿真应用中存有的缺陷,给出利用Web服务对其进行扩展的必要性和扩展途径。通过对面向服务的体系结构SOA及其实现技术Web服务的讨论,分析了通过Web服务扩展HLA使其Web使能的多种途径。文中提出一种基于代理、使用Web服务的HLA Web化扩展方法,并给出了设计方案。

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Quantum-dot laser diodes (QD-LDs) with a Fabry-Perot cavity and quantum-dot semiconductor optical amplifiers (QD-SOAs) with 7° tilted cavity were fabricated. The influence of a tilted cavity on optoelectronic active devices was also investigated. For the QD-LD, high performance was observed at room temperature. The threshold current was below 30 mA and the slope efficiency was 0.36 W/A. In contrast, the threshold current of the QD-SOA approached 1000 mA, which indicated that low facet reflectivity was obtained due to the tilted cavity design.A much more inverted carrier population was found in the QD-SOA active region at high operating current, thus offering a large optical gain and preserving the advantages of quantum dots in optical amplification and processing applications. Due to the inhomogeneity and excited state transition of quantum dots, the full width at half maximum of the electroluminescence spectrum of the QD-SOA was 81.6 nm at the injection current of 120 mA, which was ideal for broad bandwidth application in a wavelength division multiplexing system. In addition, there was more than one lasing peak in the lasing spectra of both devices and the separation of these peak positions was 6-8 nm,which is approximately equal to the homogeneous broadening of quantum dots.

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研制了有源区为InGaAs张应变体材料的1.55μm偏振不灵敏半导体光放大器(SOA)。采用束传播法计算了偏离镜面垂直方向7°的埋层波导结构模式场分布,并用平面波展开法设计了多层抗反射膜,在TE模和TM模反射率同时小于10^-4时膜厚允许误差为3%。对放大自发发射谱(ASE)和增益谱的分析表明,他们具有基本一致的偏振灵敏度。对一腔长800μm的SOA在注入电流250mA时,测量得出TE模和TM模的ASE谱偏振灵敏度小于0.5dB,增益谱3dB带宽为63nm,1550nm处光纤到光纤增益为11.9dB,3dB饱和输出功率为5.6dB,在1570nm处的噪声指数为7.8dB。而一腔长1000μmSOA耦合封装后得到的最大增益为15dB。

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A semiconductor optical amplifier gate based on tensile-strained quasi-bulk InGaAs is developed. At injection current of 80mA,a 3dB optical bandwidth of more than 85nm is achieved due to dominant band-filling effect.Moreover, the most important is that very low polarization dependence of gain (<0. 7dB),fiber-to-fiber lossless operation current (70~90mA) and a high extinction ratio (>50dB) are simultaneously obtained over this wide 3dB optical bandwidth (1520~1609nm) which nearly covers the spectral region of the whole C band (1525~1565nm)and the whole L band (1570~ 1610nm). The gating time is also improved by decreasing carrier lifetime. The wideband polarization-insensitive SOA-gate is promising for use in future dense wavelength division multiplexing (DWDM) communication systems.

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采用三元InGaAs体材料为有源区,通过直接在InGaAs体材料中引入0.20%张应变来加强TM模的增益,研制了一种适合于作波长变换器的偏振不灵敏半导体光放大器(SOA).在低压金属有机化学气相外延(LP-MOVPE)的过程中,只需调节三甲基Ga的源流量便可获得所要求的张应变量.制作的半导体光放大器在200 mA的注入电流下,获得了50nm宽的3 dB光带宽和小于0.5dB的增益抖动;重要的是,半导体光放大器能在较大的电流和波长范围里实现小于1.1dB的偏振灵敏度.对于1.55μm波长的信号光,在200 mA的偏置下,其偏振灵敏度小于1 dB,同时获得了大于14dB光纤到光纤的增益,3 dBm的饱和输出功率和大于30 dB的芯片增益.用作波长变换器,可获得较高的波长变换效率.进一步提高半导体光放大器与光纤的耦合效率,可得到性能更佳的半导体光放大器.

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数值模拟了增益钳制SOA(GC-SOA)的波长转换过程,分析了GC-SOA实现波长转换的原理.首次发现了GC-SOA波长转换中类似接通延迟的现象,这种现象将限制GC-SOA在高速波长转换中的应用.

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通过理论分析和计算表明,适当地增加反射率,在同样的工作电流下,半导体光放大器(SOA)的增益将有所增大。合理地调节抗反膜的折射率的厚度,可以使TM模的反射率R_TM在一段波长范围内大于TE模的反射率R_TE,这样的反射率分布可以相对提高TM模的增益,在一定程度上改善SOA的偏振不灵敏性,通过抗反膜的设计来辅助解决偏振不灵敏的问题,可以使SOA在有源区和波导设计中获得更大的灵活性,更好地兼顾其他的性能要求.