Nonlinear Codirectional Coupler Filter Used in WDM Networks

It is proposed a novel wavelength filter with a narrow bandwidth suitable for WDM networks, which is based upon nondegenerate four-wave mixing(NDFWM) process in the active region of a wavelength selective coupler. By separating the desired wave-mixing product on the basis of the transverse spatial mode of the electric field, a bandwidth (full width at half maximum, FWHM) of subangstrom for the filter is obtained. The selected wavelength can be tuned in the entire semiconductor gain bandwidth (～70 nm). A theoretical analysis for NDFWM effect in the filter is given. The numerical simulation has been done. The influences of configure parameters on the output efficiency, 3 dB bandwidth (FWHM) and frequency shift are discussed.     

Tunable Filters with Narrow Band in Bulk SLA for DWDM Networks

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Experimental Measurement of Fused Fiber Coupler and M-Z Interferometer Performance as WDM Devices

Abstract

An experimental study of the WDM response of fused fiber couplers and an M-Z interferometer is presented. The WDM practical implementation limits of single fused fiber couplers, along with fiber tapering measurements, were obtained. Mach-Zehnder interferometric devices based on fused fiber couplers were included in this work in order to surpass the single coupler's WDM limitations and widen the operation range of the analyzed fused fiber devices.     

Experimental Measurement of Fused Fiber Coupler and M-Z Interferometer Performance as WDM Devices

An experimental study of the WDM response of fused fiber couplers and an M-Z interferometer is presented. The WDM practical implementation limits of single fused fiber couplers, along with fiber tapering measurements, were obtained. Mach-Zehnder interferometric devices based on fused fiber couplers were included in this work in order to surpass the single coupler's WDM limitations and widen the operation range of the analyzed fused fiber devices.     

WDM光网络故障的快速共享恢复方案

在网络恢复仿真实验中发现当WDM光网络中的工作通路的链路数目为2或3时, 通路恢复资源能得到较大程度的共享. 在此基础之上, 提出了一种新的WDM光网络故障的恢复方案-分段共享恢复方案(SSR). 与现有的基于通路共享恢复方案(PSR)相比, SSR的恢复时间大大下降, 同时又基本上保持了PSR高效的资源利用率. 阐述了SSR的分段规则和实现过程, 并对SSR的性能进行了理论分析和计算机仿真.     

IP over WDM网络中可恢复的路由选择策略与算法

研究了IP over WDM网络中各层备用资源的分配问题,提出了一种新的IP over WDM网络中可恢复的路由选择策略以及应用于其中的备用路由选择算法.该策略通过层间备用资源共享,能够完全利用网络中为恢复光层故障所预留的资源来进行IP层故障恢复,从而大大提高了网络的资源利用率.对所提出的策略进行了性能分析,并给出了相应的性能指标.     

Reconfiguring the Logical Topology With Performance Guarantees in WDM Networks

To improve the network performance after traffic demand changes , reconfiguring the logical topology is necessary. We present an ILP algorithm to find out the least lightpath changes needed with guaranteed network performance.     

Wavelength Conversion in WDM All-Optical Networks and Analytical Models

This paper gives a brief introduction to the various wavelength conversion techniques. In order to explain the applications and benefits of the wavelength conversion techniques in WDM all-optical networks, several analytical models are studied.     

The Experimental Study on Wide band Tunable All-fiber Acousto-optic Filter Based on Null Coupler

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WDM光网中虚拓扑重构的优化设计

采用优化方法来研究光网络业务发生改变时的虚拓扑重构问题,并提出了相应的混合整数线性规划算法.主要的思路是当业务发生改变时,寻找既能保证网络性能又对现有业务中断最小的虚拓扑.对影响虚拓扑重构的因素进行了研究,发现,如果使网络性能达到次优而不是最优可以大大减少对现有业务的中断.     

Wavelength Filter and Converter by NDFWM in Strained Quantum Wells

A novel kind of wavelength filter and converter using nondegenerate four-wave mixing (NDFWM) in an optical amplifier with tensile and compressively strained quantum wells (T/C SQW) is reported in this paper. The configuration of the T/C SQW converting filter is designed first, followed by the establishment of the coupling model of the device. The influences of the property parameters of the optical amplifier with T/C SQW on the output efficiency, 3dB bandwidth, and the frequency shift are mainly discussed. The device can serve as both filter and wavelength converter with high conversion efficiency and narrow bandwidth on the order of 0.01 nm. Meanwhile, the frequency conversion range, which is decided by the gain bandwidth of the semiconductor media, is up to 5000 Ghz in the considered case.     

有业务量疏导能力的WDM网格网阻塞性能分析

提出一个新分析模型来计算有业务量疏导能力的波分复用(WDM)网格网的呼叫阻塞概率,WDM网络中的业务量疏导定义为复用、解复用和交换低速率业务量到高容量光路的行为.该模型首先把原始网络分解为单个子系统,然后再对这些子系统进行独立分析,最后对这些子系统的结果进行适当组合得到整个网络的解.同时,模型考虑了链路负载和链路阻塞事件之间的相关性.仿真结果表明该模型给出的结果较准确.     

Survivability in IP-over-WDM Networks: WDM Lightpath Protection versus IP LSP Protection

Abstract

This article compares the performance of WDM lightpath protection and IP LSP protection schemes for IP-over-WDM networks. A mathematical formulation of the maximum throughput problem is presented and analytical expressions for recovery time are derived for both schemes. The throughputs and recovery times are analyzed and compared. Results show that the IP LSP protection scheme presents higher throughputs then WDM lightpath protection. The IP LSP protection scheme, providing individual IP LSP protection has, however, scalability problems. This scheme presents high recovery times when a failure affects many lightpaths and many hops are allowed for the primary routes of IP LSPs.     

在WDM全光网络上构建上层网络的路由算法

在WDM全光网络上构建上层网络需要考虑上层网络的保护机制.上层网络按保护机制可分为最大故障链路数保护网和连通保护网.针对它们的不同特点给出了构建两类上层网络并使费用最低的启发式路由算法.与已有方法相比,具有算法简单,时间复杂性小,容易实用化的特点.大量的模拟计算也证明了算法的正确性.     

Survivability in IP-over-WDM Networks: WDM Lightpath Protection versus IP LSP Protection

This article compares the performance of WDM lightpath protection and IP LSP protection schemes for IP-over-WDM networks. A mathematical formulation of the maximum throughput problem is presented and analytical expressions for recovery time are derived for both schemes. The throughputs and recovery times are analyzed and compared. Results show that the IP LSP protection scheme presents higher throughputs then WDM lightpath protection. The IP LSP protection scheme, providing individual IP LSP protection has, however, scalability problems. This scheme presents high recovery times when a failure affects many lightpaths and many hops are allowed for the primary routes of IP LSPs.     

Blocking in wavelength-routed all-optical WDM networks

In this paper, we have developed a low complexity mathematical model which is used for the calculation of blocking probability of network and this model does not require any simulation statistics. The implementation of the model proposed has less complexity and the computation used in this model is quite efficient. This paper suggests an optimum path as a solution to routing problem and the appropriate number of wavelengths have also been suggested which should be free in a network to have the least blocking probability. This model can be implemented on different network topologies. Further, the model is also used to evaluate the blocking performance of NSFNet topology and hence used to improve its performance on the basis of blocking probability.     

色散位移光纤中的四波混频现象的实验研究

采用不同波长和类型的光源作为入射光信号,对色散位移光纤中的四波混频进行了实验研究。实验比较了不同色散位移光纤链组合时产生的四波混频信号的大小,研究表明,为了减小四波混频,应该在每一放大器间距内将零色散点波长距信号光波长较远的光纤铺在最接近掺铒光纤放大器处,而零色散点波长距信号光波长较近的光纤应该远离掺铒光纤放大器。对实验中的各种现象进行了理论分析,提出了一些减小四波混频的有益建议,实验结果和理论分析基本一致。     

Routing and wavelength assignment in wavelength-routed all-optical WDM networks

In this paper, low-complexity mathematical model has been developed which is used for the calculation of the blocking probability of network and this model does not require any simulation statistics. The implementation of the model proposed has less complexity and the computation used in this model is quite efficient. The routing algorithm has also been proposed in this paper depending upon the proposed model, which is very efficient in calculation and minimization of the blocking probability. This algorithm suggests an optimum path as a solution to routing problem. The wavelength assignment technique has also been suggested in this paper to minimize the blocking probability. The proposed model and algorithms can be implemented on different network topologies. Furthermore, the model, routing algorithm and wavelength assignment technique is also used to evaluate the blocking performance of NSFNet and EUPAN Network topology and hence used to improve its performance on the basis of the blocking probability.     

Blocking in wavelength-routed all-optical WDM network with wavelength conversion

The blocking probability in wavelength-routed all optical networks is very important measure of performance of the network, which can be affected by many factors such as network topology, traffic load, number of links, algorithms employed and whether wavelength conversion is available or not. In this paper, we have proposed a mathematical model to reduce the blocking probability of the WDM optical network for wavelength-convertible networks. The model can be used to evaluate the blocking performance of any network topology also it can be useful to improve its blocking performance of the given network topology. The blocking probability variation of the network for a particular load (per link) has been studied based on the load variation and total number of wavelengths used in the network. This model gives good results for high load (per link).     

Tunable Filters with Narrow-Band in Bulk SLA for DWDM Networks

The filter mechanism of a tunable filter with narrow-band in bulk semiconductor laser amplifier (SLA) is analyzed, which is suitable for dense wavelength division multiplexed (DWDM) optical fiber networks. The wavelength selectivity of the filter is derived from nondegenerate four-wave mixing (NDFWM) in semiconductor gain medium. It uses the direction of propagation to separate the desired wave-mixing product from the other light beams. The filters are shown to have very narrow passbands (subangstrom bandwidth) tunable over the entire semiconductor gain bandwidth. We gave the theoretical analysis of NDFWM effect in semiconductor gain medium is given and a set of nonlinear coupled wave equations is deduced, which are processed efficiently by Runge-Kutta method in numerical simulation. The influences of various structural parameters of the filter on the output bandwidth and efficiency were also discussed.