A generation algorithm is used to optimize a tunable optical wavelength selection switch (WSS) which is based on a cascaded silicon microring resonator. This method can help us find the optimal inter-ring coupling coefficients which can lead to smaller ripple and better wavelength selectivity over a predefined pass band range. In this paper, we validate this method by a real design and report the results of several, such GA-based WSS optimization. The results show that the GA method performs well even under the limit of physical properties of a silicon ring resonator.
Wavelength converter is widely used to resolve packet contention in optical packet switching (OPS). In this paper, fixed
wavelength converters (FWCs) are adopted as contention resolution. In order to realize an acceptable packet loss
probability, a structure called FWCA (Fixed Wavelength Converters Array) is proposed. The wavelength conversion
capacity of an FWCA is the same as that of a tunable wavelength converter, however, its wavelength conversion capacity
can be fully utilized. The performances of an optical packet switch with FWCAs and output optical buffers are evaluated
by simulation experiments.
Optical buffers and wavelength converters are two effective methods to resolve optical packet contentions in an optical packet switch. This paper focuses on the performance of fixed wavelength converters in resolving optical packet contentions. An optical packet switch with fixed wavelength converters and WDM optical buffers is proposed. The fixed wavelength converters and the WDM optical buffers are all configured as recirculation form. The performances of the optical packet switch are evaluated by simulation experiments.
In an optical packet switch, wavelength allocation algorithm has to be considered when wavelength resources are shared
among all optical packets. This paper addresses the wavelength allocation algorithms for optical packet switch with
limited wavelength converters and output WDM optical buffer. Under the condition of limited wavelength conversion,
two wavelength control strategies, i.e., greedy mode and conservative mode, are proposed. According to these two
wavelength control strategies, four wavelength allocation algorithms are presented. Performances of these algorithms are
compared in detail by simulation experiments.
In this paper, an inner wavelength method (IWM) is proposed to enlarge buffering capacity of shared FDL-buffers. In addition, an optical packet switch called Extended shared buffer type optical packet switch (Extended SB-OPS) is proposed to realize the inner wavelength method. In order to further improve performance of Extended SB-OPS, a greedy algorithm based on inner wavelength method (GA-IWM) is introduced. The performance of Extended SB-OPS is evaluated by simulation experiments.
This paper focuses on the problem of buffering performance optimization for optical packet switch with shared WDM (Wavelength Division Multiplexing) optical buffers. For this purpose, several packet scheduling algorithms are proposed to make full use of buffering resources. Influences of these algorithms on optical packet switch are evaluated by simulation experiments. Simulation results show that under different traffic load, different packet scheduling algorithms should be adopted. In addition, the performance of optical buffers also depends on the granularity of FDL.
In the paper, a new optical packet switch is proposed, which uses shared WDM buffers (fiber delay-lines) and shared tunable wavelength converters (TWCs) as contention resolution. In each fiber delay-lines, many wavelengths can be used to buffer packets at the same time. The shared TWCs have two kinds of functions, either as translators for free wavelengths in destination output fibers, or as translators for free wavelengths in the feedback FDLs. Based on this architecture, a lower packet loss rate can be achieved without the need of deploying a large number of FDLs and TWCs. The performance of the new architecture has been extensively studied by means of simulation experiments.
In this paper, a new type of p-cycles, multi-granularity flow p-cycles (MFP), is presented. A two-step approach is developed for the design of MFP with span failure recovery. Our simulation results show that MFP are more capacity-efficient than conventional span-protecting p-cycles (SP) and flow p-cycles (FP). The impacts of network topology on performance of SP, FP and MFP are evaluated. In this paper, we also propose a new p-cycle pre-selection strategy. Results show that our strategy is more efficient than two existing pre-selection strategy in p-cycle networks.
This paper considers the dynamic routing issues in WDM grooming
networks. Given network resources, a major objective of a routing
algorithm is to minimize the blocking probability of connection
requests. Wavelengths and transceivers are usually limited
resources in a network. The way to use these resources directly
determines the network performance. So the challenge is how to use
wavelength resources efficiently while keeping higher
transceiver-utilization efficiency. To solve this problem, we
develop an approach called <i>Hop Constrain Lightpath
Establishment Approach </i>(HCLEA). The main idea of HCLEA is to
guide the routing algorithms not to create inefficient long
lightpaths. Simulation results show that HCLEA does improve the
network performance in terms of transceiver-utilization
efficiency, wavelength-utilization utilization, and bandwidth
The demand to carry large amount of data as fast and as reliably as possible is continuously increasing, in parallel with formation of the information society. Nowadays, Fiber optic cables using Wavelength Division Multiplexing (WDM) are used to provide huge transport capability to support such demand effectively and economically. Each link is able to carry huge amount of traffic, thus a possible failure causes loss of tremendous data. So network survivability is highly required for such a high speed and huge capacity network. The operation of the modern telecommunication network is based on a multi-layer structure. The major reason of this multi-layer is the multiplexing hierarchy for efficient use of transmission facilities and the convenience of service and facility management. The most common example of multi-layer telecommunication network is the ATM over SDH over WDM configuration. This work investigates to the survivability of such multi-layer networks, and an integrated spare capacity dimensioning scheme, <i>joint network design</i> (<i><b>JND</b></i>) method, is proposed. Compared with single layer design (<i><b>SLD</b></i>) method, <i><b>JND</b></i> is bandwidth efficient and cost effective. The configuration problem of multi-layer fault tolerant networks is formulated as an Integer Linear Programming model. We also present a genetic algorithm approach for large networks whose size makes the ILP model difficult to use.
Integrated routing is a routing approach to support the peer interconnection model in IP over WDM networks. To have a better network link load distribution and network usage in IP over WDM networks, in which network nodes may have the ability to handle traffic in fine granularities, it is important to take into account the combined routing at the IP and WDM layers. Based upon this, this paper develops an algorithm for integrated dynamic routing of bandwidth guaranteed paths in IP over WDM networks. For newly dynamic arriving requests, as the developed algorithm takes into account the combined topology and resource usage information at the IP and WDM layers, and the routing procedure makes full use of the statistic information of the users’ bandwidth requirement and considers carefully both the routing cost and the corresponding length of the routing path, thus a better link load balancing and network usage can be achieved. Simulation results show that the developed scheme performs well in terms of performance metrics such as the number of rejected demands and the network link load balancing.
The problem of integrated routing in multifiber IP over WDM networks is studied in this paper. To solve this problem, a layered-graph is constructed and an algorithm, called <i>integrated cost-based shortest path</i> (ICSP) algorithm, is then proposed. ICSP can not only balance the traffic uniformly but also make a dynamic tradeoff between all the links in the layered-graph. A parameter <i>r<sub>l</sub></i> is introduced to characterize the <i>resource richness</i> of an IP over WDM Network. Simulation results show that ICSP outperforms other algorithms significantly in terms of blocking probability in all the cases we studied, and the performances of other algorithms are affected by <i>r<sub>l</sub></i> greatly. Because a multifiber network can be functionally equivalent to a single fiber network with limited <i>wavelength conversion</i> (WC), we make the first known attempt to investigate the impact of WC on dynamic integrated routing by studying the multifiber networks. Results show that the effect of WC depends on the granularities of <i>label switched path</i> (LSP) requests. If the granularity of each request is large, WC will improve the network performance; if the granularity of each request is small, WC will worsen the performance.
To obtain the partial information of network's resources, which indicates what fraction of each link's bandwidth, is currently used by working paths, and is used by protection paths, is feasible in IP over WDM networks using Multi-Protocol Label Switching (MPLS) technology. Based upon this partial information scenario, this paper proposes a new integrated dynamic routing algorithm of path-based protection design for IP over WDM networks. For working paths selection, the algorithm makes a tradeoff between the routing costs and the corresponding routing path length. While for protection paths, a tradeoff between the sharing of the protection paths and the associated routing path length is made. We find that the developed routing scheme is beneficial to achieve a good link load balancing. Simulation results show that the developed algorithm performs well in terms of performance metrics such as the number of rejected requests and the network link load balancing.
According to the previous researches, all-optical converters based on FWM and XGM conversion schemes at present are well suited for system use. Both performances of optical networks with FWM and XGM conversion are examined in this paper. From the results, we find that the benefit obtained by full range conversion can be achieved by using FWM conversion with the degree of conversion d=1 or 2, when the number of wavelengths on a fiber is small. But with the increase in number of wavelengths, higher conversion degree is required to achieve the performance of full range. As for the case of XGM conversion, our results show that the performance of XGM is worse distinctly than full range conversion because of its asymmetric conversion, no matter the number of wavelengths is large or small. In order to improve the performances of the networks with limited range conversion in the case of large number of wavelengths, three simple wavelength assignment algorithms (FUWC, LUWC and MSW) are proposed. We apply these algorithms to the case of Ring and Mesh-torus. Through simulation, we find that our algorithms do greatly reduce the blocking probabilities of networks with limited range conversion.