基于共享有限波长和参量波长转换器的冲突解决方案

研究了一种共享有限波长转换器(LRWC)和参量波长转换器(PWC)相结合的解决全光分组波长资源竞争的方案,并提出了PWC优先算法作为光分组交换中的波长竞争解决方案。仿真结果表明:本文结构与共享LRWC节点结构相比,减少了波长转换器的数目,并且能够明显降低光分组交换节点的分组丢包率(PLP),提高波长转换器的利用率。研究还发现,不同波长转换器配置方案对系统性能有影响。     

Variable optical delay circuit using highly nonlinear fibre parametric wavelength converters

A variable optical delay circuit that employs a fibre loop with highly nonlinear fibre parametric wavelength converters is described. The delay time is determined from the number of circulations, which is controlled by the initially selected wavelength of the signal. No additional amplifier to compensate for the circulation loss is required.     

Shared-by-wavelength-switches: a node architecture using small optical switches and shared wavelength converters

Wavelength converters can significantly improve the blocking performance of all-optical networks. The existing node architectures require large optical switches for sharing the wavelength converters. This letter proposes a new node architecture called shared-by-wavelength-switches . This node architecture requires significantly smaller and cheaper optical switches for sharing the wavelength converters while it gives nearly the same blocking performance as the existing node architectures.     

Impact of pump-phase modulation on dual-pump fiber-optic parametric amplifiers and wavelength converters

Modulation of pump phases required for suppressing stimulated-Brillouin scattering is shown to cause large power changes in both the amplified and wavelength-converted signals when dual-pump fiber-optic parametric amplifiers are used. The physical origin of power changes is related to pump-amplitude modulations caused by fiber dispersion. Analytical as well as numerical calculations show that the signal-to-noise ratio of the signal or idler may reduce to below 23 dB when pump phases change rapidly with a sharp rise time.     

Methods for full utilization of the bandwidth of fiber optical parametric amplifiers and wavelength converters

In fiber optical parametric amplifiers (OPAs), idlers are generated during the amplification process. For very wide and dense signal input spectra, idlers may overlap with signals, thereby interfering with proper operation as an amplifier. In this paper, filter-based methods to fully utilize the bandwidth of OPAs and wavelength converters in the presence of very broad signal spectra are investigated. In the basic filter setup, two parallel OPAs and two filters are used; alternatively, one can use a single OPA bidirectionally and a single filter. An interleaver-based arrangement, separating signals from idlers at the system output, with a crosstalk of below -20 dB and subdecibel bit-error-rate penalty, is experimentally demonstrated.     

Optical wavelength converters

Devices and techniques for shifting the frequency/wavelength of an optical carrier wave are reviewed, with particular reference to applications in wavelength/frequency division multiplexed optical communication systems. Considered first are devices which make use of semiconductor laser amplifiers or oscillators. Some of these techniques come close to satisfying the requirements for a suitable wavelength shifter, though none appear to offer the potential for a transparent network independent of data modulation format. A second main category, using nonlinear optical materials, promises to satisfy the requirements for frequency translation in a network which is fully transparent to the modulation format. However, the conversion efficiencies currently available appear too low for cost-effective communication systems engineering so that further advances in nonlinear optical materials/techniques are still required. It seems likely that guided wave techniques will provide the best means of improving the efficiency by increasing the interaction length and the optical intensity for a given power. Schematic examples of such a converter are discussed. All of the existing techniques have some deficiencies compared to an ideal system so that wavelength conversion for optical communication systems is still a problem in search of a good solution     

Performance analysis of variable optical delay circuit using highly nonlinear fiber parametric wavelength converters

The performance of a variable optical delay circuit that employs a fiber loop with highly nonlinear fiber parametric wavelength converters is discussed using both experiments and simulations. In our optical delay circuit, the delay time is determined from the number of circulations, which is controlled by the initially selected wavelength of the optical signal. We discuss the factors that limit the number of circulations described in our previous paper, derive the parameters that provide good performance levels, and confirm the performance by simulation. The simulated results indicate that 100 wavelength conversions can be achieved, namely, 100 different delay times can be given to optical packets.     

Dynamically concatenated wavelength converters

An architecture is proposed for a wavelength-division-multiplexed (WDM) optical packet or circuit switch in which a bank of limited-range wavelength converters is shared among all input fibers, and in which any subset of converters can be dynamically concatenated (cascaded) to yield a wider conversion range for a packet that would otherwise be dropped because all unused wavelengths in its desired output fiber lie outside the range of a single converter. A probabilistic model of a switch is used to numerically determine the improvement in packet-drop probability achieved by dynamically concatenating converters.     

波长转换器的研究

讨论了基于半导体激光放大器的波长转换器，它是光交换块中的关键元件，也是未来通信系统中的关键元件。从理论上分析了各种半导体光放大器转换器的转换原理，并给出了它们的种种结构。     

Algorithms for allocating wavelength converters in all-opticalnetworks

In an all-optical wide area network, some network nodes may handle heavier volumes of traffic. It is desirable to allocate more full-range wavelength converters (FWCs) to these nodes, so that the FWCs can be fully utilized to resolve wavelength conflict. We propose a set of algorithms for allocating FWCs in all-optical networks. We adopt the simulation-based optimization approach, in which we collect utilization statistics of FWCs from computer simulations and then perform optimization to allocate the FWCs. Therefore, our algorithms are widely applicable and they are not restricted to any particular model or assumption. We have conducted extensive computer simulations on regular and irregular networks under both uniform and nonuniform traffic. Compared with the best existing allocation, the results show that our algorithms can significantly reduce: (1) the overall blocking probability (i.e., better mean quality of service) and (2) the maximum of the blocking probabilities experienced at all the source nodes (i.e., better fairness). Equivalently, for a given performance requirement on blocking probability, our algorithms can significantly reduce the number of FWCs required     

An optical packet contention resolution supporting QoS differentiation with LRWC wavelength converters for OPS

The wavelength conversion is regarded as an effective way to resolve the optical packet contention in the wavelength domain for optical packet switching. An optical packet switching node, based on shared-per-node equipped with limited range wavelength converters and parametric wavelength converters (SPN-LP), is designed to further reduce optical packet loss probability. A novel optical packet contention resolution with priority differentiation wavelength scheduling algorithm to support quality of service (QoS) for the SPN-LP architecture is put forward in the article. The simulation results show that proposed optical packet resolution enables a good QoS differentiation, namely the high priority contending optical packet has the sufficient low packet loss probability.     

Efficient routing and wavelength assignment for reconfigurable WDM ring networks with wavelength converters

We consider the problem of wavelength assignment in reconfigurable WDM networks with wavelength converters. We show that for N-node P-port bidirectional rings, a minimum number of /spl lceil/PN/4/spl rceil/ wavelengths are required to support all possible connected virtual topologies in a rearrangeably nonblocking fashion, and provide an algorithm that meets this bound using no more than /spl lceil/PN/2/spl rceil/ wavelength converters. This improves over the tight lower bound of /spl lceil/PN/3/spl rceil/ wavelengths required for such rings given in if no wavelength conversion is available. We extend this to the general P-port case where each node i may have a different number of ports P/sub i/, and show that no more than /spl lceil//spl sigma//sub i/P/sub i//4/spl rceil/+1 wavelengths are required. We then provide a second algorithm that uses more wavelengths yet requires significantly fewer converters. We also develop a method that allows the wavelength converters to be arbitrarily located at any node in the ring. This gives significant flexibility in the design of the networks. For example, all /spl lceil/PN/2/spl rceil/ converters can be collocated at a single hub node, or distributed evenly among the N nodes with min{/spl lceil/P/2/spl rceil/+1,P} converters at each node.     

An optimization model for placement of wavelength converters to minimize blocking probability in WDM networks

The introduction of wavelength converters in wavelength division multiplexing (WDM) networks can reduce the blocking probabilities of calls. In this paper, we study the problem of placing a given number of converters in a general topology WDM network such that the overall system blocking probability is minimized. The original contributions of this work are the following: 1) formulation of success probability in a network as a polynomial function of the locations of converters; 2) proposal of an optimization model of the converter placement problem as the minimization of a polynomial function of 0-1 variables under a linear constraint, so that standard optimization tools can be employed to solve the problem; and 3) design of a search algorithm that can efficiently find the optimal solution to the converter placement problem. Experiments have been conducted to demonstrate the effectiveness of the proposed model and the efficiency of the algorithm.     

All-optical wavelength conversion with large wavelength hopping by utilizing multistage cascaded SOA-based wavelength converters

A novel broadband wavelength converter by multistage cascaded semiconductor optical amplifier (SOA)-based wavelength converters is proposed. We have demonstrated, for the first time, broadband wavelength conversion in the wavelength range of 1320-1610 nm by using three-stage cascaded SOA-based wavelength converters with each different gain band.     

WDM网络中确定波长变换器位置与数目的启发式算法

该文首次研究了波分复用(Wavelength Division Multiplex,WDM)网络中如何在最佳节点中确定波长变换器数目的算法,设计了3种启发式算法,通过在NSFNET(the U.S.NationalScience Foundation backbone NETwork,美国科学基金会骨干网络),ARPANBT(the AdvancedResearch Projects Agency NETwork,美国高级研究规划局网络),CERNET(China Educationand Research NETwork,中国教育科研网络)上的仿真,比较了3种算法的性能差异,得出算法1的性能最优,且复杂度最低。另外,通过比较在部分节点以及全部节点中运用算法1确定波长变换器的数目,得出:在WDM网络中,在部分节点中装配有限的波长变换器也可以达到全部节点中装备波长变换器的性能,并且还可以降低光交叉连接设备(Optical Cross-Connects,OXC)的成本,减少复杂的控制。     

双波长输出KTP光学参量振荡器

随着人眼安全激光器在军事上的广泛应用,光电对抗需要一种能够同时输出一定能量1.5x μm激光和1.06 μm激光的OPO装置.对OPO装置的工作物质、系统结构和各项参数进行设计,并研制出1.57μm激光和1.06 μm双波长非临界相位匹配KTP光学参量振荡器(OPO).使用Nd:YAG激光器1.06 μm激光泵浦,获得12 mJ/Pulse的1.57μm激光和57 mJ/Pulse的1.06μm激光,重复频率为1 Hz,单谐振效率达到15%,光束发散角约为3 mrad.     

Study of multicast wavelength arrangement for maximizing network capacity in WDM networks with sparse wavelength converters

The issue of wavelength assignment is one of the most important factors that affect the capacity for the deployment of optical networks. This issue becomes more critical for multicast connections, especially when the network nodes have no wavelength conversion capability. Although the wavelength assignment can be more flexible if each node can perform wavelength conversion, the deployment cost increases accordingly. A compromise is to support a limited portion of conversion nodes in the WDM network. We propose a systematic approach for the wavelength assignment of multicast connections in WDM networks with sparse wavelength conversion nodes. The efficiency of the arrangement of wavelength is measured by its influences on the available capacity of the network and the consumption of wavelengths. By using the proposed approach, the Static Cost Greedy (SCG) algorithm [8] can be easily extended to be applicable in a Sparse Wavelength Conversion Network (SWCN). In addition, instead of SCG, the Minimum-Effect-First (MEF) algorithm is proposed to maximize the network capacity during wavelength assignment. We compare the performance of the proposed MEF methods with the extended SCG scheme through exhaustive simulations. The experimental results indicate that the proposed MEF schemes demonstrate much better performance than the SCG scheme. We also found that the performance is not always improved proportionally to the increment of the wavelength conversion nodes. The improvement reaches saturation when the number of conversion nodes is above 35% of the total number of nodes.