Noise and crosstalk limitations in optical cross-connects withreshaping wavelength converters

Noise and crosstalk are two important limiting factors in optical networks with optical cross-connects (OXC's). If reshaping wavelength converters are used in the OXC nodes, noise and crosstalk are transformed into timing jitter which accumulates in the network and limits the performance. A method to evaluate the influence of jitter caused by noise and crosstalk in cascaded OXC's is presented and applied to three different OXC architectures, taking both coherent and incoherent crosstalk into account. In the analyzed architectures, the losses in the OXC and the coherent crosstalk is found to be the most important limitations     

多波长光交叉连接节点的优化设计

在WDM光网络中，光交叉连接（OXC）节点的串扰是限制网络规模的关键因素，提高光开关的隔离度是降低OXC串扰的一条途径，文章比较了3种不同结构的光开关矩阵的串扰特性，在此基础上对OXC节点进行了优化设计，改进后的OXC节点的串扰性能大的改善，网络规模也因此而得到了极大地扩展。     

Analysis of Crosstalk Induced by Optical Cross-Connection in Multiwavelength Networks

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WDM光网络中OXC结构对带内串扰积累的影响

串扰是波分复用(WDM)光网络中光交叉连接(OXC)投入实用的最大障碍。理论分析了基于扩展Benes(DB)结构和改进扩展Benes(GMDB)结构的3种典型OXC节点结构中的带内串扰,并数值模拟了基于两种结构的OXC节点中带内串扰的积累特性。结果表明,基于DB结构和GMDB结构的OXC节点可以完全消除低于二阶的各类串扰。发现基于GMDB结构的OXC节点能大大减少带内串扰的积累,与基于DB结构的OXC节点相比,基于GMDB结构的OXC节点对光开关串扰系数的要求放宽了5dB,说明OXC节点结构的选择对消除串扰尤为重要。     

WDM动态光学交叉互连中同源串扰的研究

研究了在波分复用（ＷＤＭ）全光网中,串扰对动态路由光交叉互连（ＯＸＣ）性能的影响。理论分析指出,在动态路由的ＯＸＣ中,由于信号光泄漏后经过不同的光路而造成的同源串扰对系统性能的影响要比其他类型的串扰影响大。还提出了一种新的解决方案。理论计算表明,这种优化后的ＯＸＣ结构能够有效地减小同源串扰的影响,从而以很小的硬件成本提高ＯＸＣ的性能。     

声光调谐滤波器用于OXC中的串音分析

分析了声光可调谐滤波器（AOTF）用于光交叉连接（OXC）系统中的各种串音。讨论了各种相应的串音抑制方法。在波长分组的概念基础上提出了一种新的不对称波长扩展OXC结构。     

Broadband building blocks [optical networks]

This article has focused on optical networks using WDM to provide broadband network solutions with increased functionality, capacity, and reach. The building blocks in this type of networks, i.e., OADMs and OXCs, have been discussed in detail. The different architectures and technology options used in these types of nodes have been investigated. A comparison between WS and BS OADM architectures has been given, while OXCs have been classified into opaque and transparent. The WS and B&S transparent OXC architectures have been discussed in detail, and the various technology options in terms of optical switching have been covered. The system performance of OADMs and OXCs including their cascadability has been analyzed in terms of OSNR, crosstalk, amplifier transients, and filter concatenation effects.     

基于低串扰OXC的自动链路交换系统的设计与实现

介绍了基于低串扰OXC的自动链路交换系统的设计与实现,详细阐述了系统中OXC路由模块的硬件设计及实验方案.实验网络可以完成端到端光链路的自动建立.     

8/spl times/8 optical switch matrix using generalized Mach-Zehnder interferometers

We report an 8/spl times/8 strictly nonblocking optical cross connect (OXC) using multimode imaging (MMI)-based generalized Mach-Zehnder (MZ) interferometers realized in the silica-on-silicon planar waveguide system. Employing a router-selector architecture, this MMI-MZ OXC design results in a significantly smaller device than conventional directional-coupler based implementations. An average insertion loss of 6 dB and crosstalk of -34 dB, is demonstrated for the 8/spl times/8 OXC.     

Crosstalk analysis of multiwavelength optical cross connects

This paper presents the results of a crosstalk analysis of four optical wavelength division multiplexed (WDM) cross-connect (OXC) topologies. An optimal set of parameters is determined to reduce the total crosstalk. The scalability of the topologies is presented in terms of wavelengths and input fibers. The total crosstalk in function of the number of cascaded OXC's is compared for the four topologies     

WDM网络中波长信道的误码率估计

本文建立了完整的WDM光网络节点的同频串扰理论分析模型，考虑光放大器ASE噪声的影响，采用重要性采样技术进行数值仿真，得出某一波长信道中串扰导致的误码率，讨论波长个数、同源串扰数及消光比等因素对系统性能的影响，并与高斯近似法的结果进行了比较。     

用于全光网的光交叉连接技术研究

介绍了用于全光网的光交叉连接的主要特点、构成部件和应用 ,详细讨论了其结构 ,并特别探讨了其用于实现全光交换的核心部件光开关的主要技术     

一体化OADM/OXC节点降低串扰结构研究

提出并分析了一体化光分插复用 /光交叉连接 (OADM/OXC)的降低串扰节点结构。在波分复用 (WDM )光传送网络中 ,一体化节点可以同时完成对光通道的上下路与交叉连接功能。与传统结构节点相比 ,该结构中使用一组 1× 2和 2× 1光开关与小规模的光交叉连接阵列实现光通道的上下路与交叉连接。仿真结果证明 ,该结构中由于同频串扰造成的功率代价显著下降。     

N/spl times/N multiwavelength optical cross-connect based on tunable fiber Bragg gratings

We propose a highly channel-scalable multiwavelength optical cross-connect (OXC) based on tunable fiber Bragg gratings (TFBGs), which is suited for metropolitan or access networks. N/spl times/N OXC of this architecture is constructed by cascading independently operating routing modules, and each routing module consists of fiber Bragg gratings (FBGs) with fixed center wavelength and a TFBG-based N/spl times/N routing block. The group velocity dispersion (GVD) and intraband crosstalk (IXT) are the main signal-degrading factors arising from the operation of the proposed OXC, and the effectiveness of each factor is individually investigated numerically for 10-Gb/s nonreturn-to-zero (NRZ) systems. Then, a routing experiment of the proposed OXC is carried out in a 3/spl times/3 routing block configuration, using OC-192 signals with channel spacing of 0.8 nm. Finally, the installable size of the proposed OXC and network scale are estimated by resorting to a comprehensive numerical simulation of 10-Gb/s NRZ signal transmission.     

A comprehensive study on next-generation optical grooming switches

This paper investigates the characteristics and performance of different optical grooming switches, i.e., optical cross-connects (OXCs) capable of traffic grooming, under a dynamic traffic environment. We present four optical grooming-OXC architectures, namely, single-hop grooming OXC, multihop partial-grooming OXC, multihop full-grooming OXC, and light-tree-based source-node grooming OXC. After exploring their grooming capabilities, we propose three grooming schemes and two corresponding algorithms, grooming using auxiliary graph and grooming using light-tree. Through the algorithms, we evaluate the performance of different optical grooming OXCs in a dynamic traffic environment under different connection bandwidth-granularity distributions. Our investigation uncovers the following results: (1) the multihop full-grooming OXC can achieve the best network performance, but it may encounter cost and scalability constraints; (2) by using significantly less low-granularity electronic processing and intelligent traffic-grooming algorithms, the multihop partial-grooming OXC shows reasonable network performance and, hence, can be viewed as a cost-effective alternative when a network node does not require full-grooming capability; (3) the single-hop grooming OXC may cause a large amount of capacity waste and lead to poor network performance; and (4) through its multicast capability, a light-tree-based source-node grooming OXC can significantly out-perform the performance of a single-hop grooming OXC in terms of network throughput and network resource efficiency. From our results, we also observe that the connection bandwidth-granularity distribution has a large impact on network throughput and network resource efficiency and, therefore, should be carefully considered for network design and traffic provisioning.     

WDM光网络非相干串扰实验研究

在WDM光网络系统中,节点如OXC和OADM采用的光器件其非理想性积累构成系统串扰问题。本文提出了WDM光网络系统中串扰问题分析的一般数学模型,根据模型分析比较了WDM光网络中相干串扰和非相干串扰的区别。实验研究了不同非相干串扰代价条件下,对应WDM光网络系统的功率代价。对应1dB功率代价下,实验得出WDM光网络对应非相干串扰代价容限小于－20.8dB的结果。实验结果对于WDM光网络组网规划有一定的参考意义。     

Coherent and incoherent crosstalk in WDM optical networks

The impact of coherent and incoherent crosstalk on an optical signal passing through optical cross-connect nodes (OXC's) in wavelength division multiplexing (WDM) optical networks is studied, and the analytical expressions are given. Such crosstalk will be generated when the optical propagation delay differences of optical paths in an OXC do not exceed the coherent time of the lasers. While causing fluctuation of signal power, coherent crosstalk may cause noise or not, depending on the relationship between the optical propagation delay differences and the time duration of one bit of the signal. Incoherent crosstalk may cause very high noise power, because it can be a coherent combination of crosstalk contributions. The statistical impact of all crosstalk contributions on signal is studied by simulation, and the concept of quantile is proposed to relax the crosstalk specification requirement for components. The crosstalk specification requirements are then obtained for components used in WDM optical networks with different scales     

Buffered time-wavelength cross-connects: Architectures and performance evaluation

An all-optical approach to reduce the speed mismatch between electronic sources and high-speed wavelength channels is to time-division multiplex low-capacity circuits onto each wavelength. In such a Time-Wavelength-Switched Network (TWSN), the optical crossconnects (OXCs) are configured to switch time-wavelength-slots within the network. The OXCs can be deployed with a bank of fiber delay lines (FDLs) to improve the connection slot scheduling and decrease the connection blocking probability. In this paper, we consider the two broad scenarios of sharing a bank of FDLs: shared per output link (SPL) and shared per crossconnect (SPC). We present several OXC architectures and develop graph formulations that can be used to optimally solve the scheduling problem. We also incorporate wavelength conversion and feedback in these architectures and study the impact of various FDL configurations on a crossconnect’s performance. Results using numerical simulations show that the FDL configuration does in fact affect the performance of the OXC. We also evaluate the performance of an OXC equipped with an FDL bank for both the SPL and SPC scenarios by considering sparse wavelength converters (limited number of full range wavelength converters). Results show that using sparse converters along with FDLs could provide significant benefits.     

下一代IP核心传输网络结构分析

比较了IP直接传输和通过ATM网络传输IP业务的特点 ,详细描述了下一步以IP为核心业务的三种可能的传输网络结构 :DWDM线路系统组成的SONET环、DWDM线路系统连接的交叉连接系统构成的网状网和无交叉连接设备的DWDM光纤网 ,以及各种结构中主要管理功能的实现 ,并对各种传输网络结构的性能和成本进行了具体分析