A New Scheme to Realize Crosstalk-Free Permutation in Vertically Stacked Optical MINs*

Vertical stacking is a novel alternative for constructing nonblocking multistage interconnection networks (MINs). Rearrangeably nonblocking optical MINs are attractive since they have lower complexity than their strictly nonblocking counterparts. In this paper, we study the realization of crosstalk-free permutations in rearrangeably nonblocking, self-routing banyan-type optical MINs built on vertical stacking. An available scheme for realizing crosstalk-free permutation in this type of optical MINs requires to first decompose a permutation into multiple crosstalk-free partial permutations based on the Euler-Split technique, and then to realize them crosstalk-free in different planes (stacked copies) of the MIN simultaneously. The overall time complexity of this scheme to realize a crosstalk-free permutation in an N × N optical MIN is O(N log N) which is dominated by the complexity of crosstalk-free decomposition. In this paper, we propose a new scheme for realizing permutations in this class of vertically stacked optical MINs crosstalk-free. The basic idea of the new scheme is to classify permutations into permutation classes such that all permutations in one class share the same crosstalk-free decomposition pattern. By running the Euler-Split based crosstalk-free decomposition only once for a permutation class and applying the obtained crosstalk-free decomposition pattern to all permutations in the class, crosstalk-free decomposition of permutations can be realized in a more efficient way. We show that the number of permutations in a permutation class is huge (N!)^N when log₂N is even and (2N!)^N/2 when log₂N is odd), and thus the average time complexity of crosstalk-free decomposition of a permutation becomes O(N).     

A New Architecture for Nonblocking Optical Switching Networks

With the current technology, all-optical networks require nonblocking switch architectures for building optical cross-connects. The crossbar switch has been widely used for building an optical cross-connect due to its simple routing algorithm and short path setup time. It is known that the crossbar suffers from huge signal loss and crosstalk. The Clos network uses a crossbar as building block and reduces switch complexity, but it does not significantly reduce signal loss and crosstalk. Although the Spanke's network eliminates the crosstalk problem, it increases the number of switching elements required considerably (to 2N ² - 2N). In this paper, we propose a new architecture for building nonblocking optical switching networks that has much lower signal loss and crosstalk than the crossbar without increasing switch complexity. Using this architecture we can build non-squared nonblocking networks that can be used as building block for the Clos network. The resulting Clos network will then have not only lower signal loss and crosstalk but also a lower switch complexity.     

Scalability of Optical Networks: Crosstalk Limitations

Optical networks represent a promising solution for the future high capacity and flexible transport network. This paper presents a model for the performance evaluation of optical networks with respect to linear crosstalk and accumulated spontaneous emission noise. The proposed model is intended for the evaluation of the crosstalk requirements on the devices needed to support an optical network with a certain number of nodes and with a given level of bit-error rate.     

光网络中大功率信号引起的带内串扰攻击研究

分析了光网络中大功率信号引起的带内串扰攻击,攻击信号功率和光开光串扰系数是带内串扰攻击对用户信号质量产生破坏影响的主要因素.在VPI仿真软件中搭建实验系统,以误码率为评价指标,定量研究了带内串扰攻击对用户信号质量的影响及其攻击传播能力.结果表明,当光开关串扰系数为-20 dB、初始攻击信号功率高于用户信号功率20 dB以上时,在OXC1处,经过第一级和第二级光开关的用户信号会受到攻击影响,经过第三级光开关的用户信号几乎不受攻击影响.带内串扰攻击具有一定的攻击传播能力,当初始攻击信号功率高于用户信号功率27dB、光开光串扰系数为-20 dB时,初始攻击信号的攻击能力可传播至OXC3,同时,二阶攻击信号基本不具备攻击传播能力.     

基于Banyan网络的无阻塞SiO2波导4×4矩阵光开关

提出了一种基于Mach-Zehder干涉仪(MZI)结构开关单元和Banyan网络的严格无阻塞4×4矩阵光开关.相对于Crossbar结构的7级单元级联,Banyan结构只需3级连接.分析了Banyan网络中交叉连接损耗与交叉角度的关系,交叉角30°时损耗为0.09 dB.优化设计了MZI开关单元结构,并制作了2×2光开关,测得插入损耗(IL)为-14 dB、串扰(XT)为-38 dB和功耗为450 mW.设计了基于Banyan网络的4×4光开关,连接波导交叉角为30°.基于光波导平面光波线路(PLC)技术,制作了严格无阻塞的SiO2波导4×4矩阵光开关,测得平均IL为3.95 dB、通道XT为-37 dB、偏振相关损耗(PDL)为0.4 dB、单通道开关功率约为670 mW及开关响应时间小于1 ms.     

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。     

光网络中大功率带间串扰攻击研究

理论分析了光网络中大功率带间串扰攻击的产生机理,得出了攻击信号功率和光纤非线性折射率系数是大功率带间串扰攻击对用户信号质量产生破坏影响的主要因素。在VPI中搭建仿真实验系统,以误码率为信号质量评价指标,研究了大功率带间串扰攻击对用户信号质量的攻击影响及其攻击传播能力。结果表明,大功率带间串扰攻击会造成和攻击信号使用同一条光纤进行传输的用户信号质量劣化。攻击信号功率越高,信道间隔距攻击信号越近,光纤非线性折射率系数越大,用户信号受攻击影响越严重。大功率带间串扰攻击具有一定的攻击传播能力,当攻击信号功率高于用户信号功率27 dB时,攻击信号的攻击影响可传播至第四个光交叉连接器。     

基于Banyan网络的无阻塞SiO2波导4×4矩阵光开关

提出了一种基于Mach-Zehnder干涉仪（MZI）结构开关单元和Banyan网络的严格无阻塞4×4矩阵光开关。相对于Crossbar结构的7级单元级联，Banyan结构只需3级连接。分析了Banyan网络中交叉连接损耗与交叉角度的关系，交叉角30°时损耗为0．09dB。优化设计了MZI开关单元结构，并制作了2×2光开关，测得插入损耗（IL）为-14dB、串扰（XT）为-38dB和功耗为450mW。设计了基于Banyan网络的4×4光开关，连接波导交叉角为30°。基于光波导平面光波线路（PLC）技术，制作了严格无阻塞的SiO2波导4×4矩阵光开关，测得平均儿为3．95dB、通道XT为-37dB、偏振相关损耗（PDL）为0．4dB、单通道开关功率约为670mW及开关响应时间小于1ms。     

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

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AWG作光路分插复用器串扰对信道数的影响

研究了阵列波导路由器作光路分插复用器（OADM）串扰的影响,其路由器含有m个上路/下路信道和n个传输信道。理论分析表明:随着上路/下路信道m和传输信道n的增加,串扰使OADM的信噪比QCT,成非线性下降、由于在阵列波导路由器中存在串扰,限制了基于 OADM的网络复用信道数。     

全光网络中同频串扰的研究

全光网络中的同频串扰将对系统性能产生严重影响。本文理论分析了同频串扰对强度调制－直接检测系统的影响,并进行了实验研究。文中讨论出应串扰对系统的影响与各参数的关系,为各种情况下全光网络的设计提供了指导。     

波长转换对光交叉连接节点中串扰的影响

针对具有波长转换功能的节点共享型和链路共享型光交叉连接(OXC)节点,分析了相干串扰和非相干串扰引起的功率代价并进行了仿真计算.结果表明,相干串扰引起的功率代价远远大于非相干串扰,尤其当时间延迟小于激光器的相干时间并小于码型周期时,串扰引起的功率代价最大.为达到一定的系统性能,分析了WDM光网络对器件的要求,并比较了波长转换器的加入对OXC节点串扰的影响,结果发现,加入波长转换器后,系统的功率代价有一定的改善,相同条件下波长转换器的加入对器件的隔离度要求降低2 dB.     

完全无阻塞光开关阵中构成重排无阻塞光开关阵的数目

本文讨论了在４×４网结型完全无阻塞光开关阵中，构成４×４重排无阻塞光开关阵的组合数。由分析计算可得到４８种组合。文中把这些组合一一列出。结果表明，当一个４×４网结型开关阵的１６个开关中有若干个失效时，有可能把这个开关阵变成一个４×４重排无阻塞开关阵。     

频谱分割WDM无源光网络中的损耗和串扰研究

提出了一种频谱分割WDM无源光网络（PON）的损耗和串扰模型，通过理论分析和数值计算，得到了损耗和串扰与光源带宽、复用器参数、信道数以及信道失配系数等系统参数的关系，对频谱分割WDM PON的设计具有一定的指导意义。     

无源光网络的初步升级方案

利用 13 10nm/ 15 5 0nm粗波分复用器 (CWDM)与 15 5 0nm光纤型带内耦合器 (OFIBC) ,提出了无源光网络(PON)的初步升级方案 ,CWDM与OFIBC复用器大的通带间隔与温度不敏感性保证了可以采用现行的无制冷的F P腔激光器 ,实验表明根据OFIBC的通带 ,选择激光器中心波长 ,系统可以达到具有较小的功率损耗与串扰。     

基于双参数比较的光网络多点带内串扰攻击定位算法

分析了光网络中带内串扰攻击的攻击源特点,提出了一种基于双参数比较的分布式多点带内串扰攻击定位算法,该算法通过同时比较节点本身检测到的光信噪比参数和信号功率参数以及直接上游节点检测到的对应参数来判断攻击源的位置。仿真结果表明,该算法能够实现对多点攻击情况下攻击源的快速准确定位。     

光学全交叉网络与SW榕树（F＝S＝2）网络拓扑等价的多样性

本文对有关互连网络拓扑等价的分析方法作了简单评述。并采用互连网络拓扑等价的图分析法分析了自由空间光学互连全交叉网络与ＳＷ榕树网络的拓扑等价及其多样性，拓展了全交叉网络在数字光计算、光子交换及多处理机系统的潜在应用。     

3R光电波长变换器对WDM网中串扰的影响

具有光叉连接（ＯＸＣ）节点的波分复用（ＷＤＭ）光网络中,串扰是一个重要的限制因素。本文针对基于分送耦合开关的ＯＸＣ结构,分析了相干和非相干串扰引入的光功率恶化并进行了仿真计算。结果表明相干串扰是影响传输质量的重要因素,串扰引起的光功率恶化主要取决于复用波数Ｍ,而与输入光纤数Ｎ关系不大。如果在ＯＸＣ节点内采用３Ｒ光电波长变换器（ＯＥＷＣ）,串扰对系统的影响会降低。     

A Low‐Crosstalk Design of 1.25 Gbps Optical Triplexer Module for FTTH Systems

In this paper, we analyzed and measured the electrical crosstalk characteristics of a 1.25 Gbps triplexer module for Ethernet passive optical networks to realize fiber‐to‐the‐home services. Electrical crosstalk characteristic of the 1.25 Gbps optical triplexer module on a resistive silicon substrate should be more serious than on a dielectric substrate. Consequently, using the finite element method, we analyze the electrical crosstalk phenomena and propose a silicon substrate structure with a dummy ground line that is the simplest low‐crosstalk layout configuration in the 1.25 Gbps optical triplexer module. The triplexer module consists of a laser diode as a transmitter, a digital photodetector as a digital data receiver, and an analog photodetector as a cable television signal receiver. According to IEEE 802.3ah and ITU‐T G.983.3, the digital receiver and analog receiver sensitivities have to meet ‐24 dBm at BER=10^?12 and ‐7.7 dBm at 44 dB SNR. The electrical crosstalk levels have to maintain less than ‐86 dB from DC to 3 GHz. From analysis and measurement results, the proposed silicon substrate structure that contains the dummy line with 100 μm space from the signal lines and 4 mm separations among the devices satisfies the electrical crosstalk level compared to a simple structure. This proposed structure can be easily implemented with design convenience and greatly reduce the silicon substrate size by about 50 %.