Packet Ring transport technology combines the simplicity of Ethernet and survivability of SONET and attracts more and more interests of researches. However, electrical processing cost will also be very high as data rate grows to gigabit level, which lowers its efficiency. This paper examines the value of optical bypass approach by minimizing the traffic to be processed in electrical domain. An Integer Linear Program (ILP) formulation is presented to solve this problem and results with different traffic patterns are given, which shows one more wavelength can bring notable electrical processing cost savings in the case of a small number of multiplexed wavelengths in one channel.
The rapid progress on optical performance monitoring technology makes it possible for optical network designers to guarantee the QoS quality of lightpaths in Wavelength Division Multiplexing (WDM) network. This article describes the basic idea of online QoS guarantee scheme, focusing on the distributed optical noise figure calculation algorithm and optimal design heuristic.
This paper studies the problem of virtual topology reconfiguration for changing traffic patterns in wavelength-routed network. We formulate it as an optimization problem, which tries to find out the virtual topology with least lightpath changes with network performance within given bound, when traffic demand imposed on wavelength-routed network changes. Average Packet Hop Count (APHD) is used to measure the degree of network performance. A linear formulation is presented and solved by MILP (Mixed Integer Linear Programming) method. Then we analyze the relationship between lightpath changes and degradation degree of performance. It can be seen that a large cost reduction for reconfiguration can be achieved by giving up a small amount of network performance.
Since Resilient Packet Ring has been the subject of intense research, it is necessary to study and analyze the performance of technology. In this paper, based on queuing theory and M/G/1/K queuing system, the average packet transfer delay following Darwin preliminary draft is analyzed. The results show that high priority traffic gets the lowest delay and the difference between medium and low priority traffic is small. In addition, the larger the network, the less is the difference. Maximum network throughput is also obtained in theory, which is instructive to further promote the related standard and even to design network in practice.
In IP over WDM networks, when a failure (a link failure) occurs, the service restoration can be implemented by dynamic routing in IP layer. But it needs the virtual topology remains connected after any physical link failure. Otherwise, IP layer cannot find an alternate path to restore the service. The problem of routing logical links (lightpaths) on a physical network in a way that the logical topology remains connected in the event of single physical link failure is called survivable routing. Our aim is to find out the minimum wavelength requirement for survivable routing.
In short, we address the survivable routing problem by proposing a new ILP algorithm which works well with sparse-connected logical topologies. The necessary and sufficient conditions for survivable routing are simplified, which greatly reduces the number of survivable constraints. Based-on the simplified conditions, a new ILP formulation with K-shortest paths as alternate paths for a logical link is presented, which mainly reduces the number of variables needed to be solved. It will be demonstrated that the time needed to solve such an ILP is relatively small. Finally, numerical results are given and discussed to show the effectiveness of our algorithm.
The blocking performance of two types of all-optical networks: wavelength-selective (WS) and wavelength-interchangeable (WI) networks, is studied. Efficiency of different dynamic routing and wavelength assignment (RWA) algorithms, including adaptive routing algorithms and dynamic alternate routing algorithms, is investigated. Dynamic wavelength assignment combined with adaptive route selection algorithm is also presented and investigated. Numerical results show that multifiber WS networks may provide a viable and economical alternative to WI networks, and dynamic alternate routing algorithms is also a good substitute to adaptive routing algorithms. The presented dynamic wavelength assignment combined with adaptive route selection algorithms exhibit better efficiency than other ones. The study also shows that the efficiency of different dynamic RWA algorithms is dependent with different topologies, and the performance gain of wavelength conversion in regular topology is not as significant as in irregular topology networks, meanwhile, the efficiency of different dynamic RWA algorithms is closely related with the number of alternate routes.
In this paper, we discuss the load balancing issues for wavelength-routed optical networks. After a definition of load balancing factor, which evaluates the fairness of the wavelength usage on each link, a new Integer Linear Program (ILP) formulation is proposed for routing and wavelength assignment for WP and VWP-RWA scheme. As the ILP is time-consuming for large-scale networks, an effective heuristic algorithm is given. In this paper, we use three metrics to quantify the performance improvement by our method: Load balancing factor FF, wavelength requirement N<sub>λ</sub> and wavelength reusability ρ. In both WP and VWP schemes, our load balancing algorithm achieves much better performance than Fixed-shortest-path and alternate-shortest-paths routing algorithms.
The recent increase in the transmission speed and bandwidth has resulted in the emergence of new networking solution, Resilient Packet Ring. In this paper, we firstly study the spatial reuse protocol in Resilient Packet Ring. Then based on node model, we discuss several access control mechanisms, including traffic shaping and Virtual Destination Queuing. Finally, a new effective fairness algorithm is presented. In order to ensure the requirement of high priority traffic and avoid high priority traffic taking up all of capacities, the algorithm proportionally assigns the fair rate to different traffic in a theoretical optimal way according to the service priority.
Several tunable optical splitter techniques and some of their applications, including some prospective schemes, are discussed in this paper. It is explained by specific examples that all the variable transmission/reflection film technology, variable fiber couple length technology, acousto-optic/electro-optic deflection technology, and Mach-Zehnder interference technology are the capable technologies to realize tunable optical splitter, and tunable splitter technology to be applied to optical transmission networks, other devices and optical measurements.
A kind of multi-wavelength labeled optical packet switching technology is presented, in which optical header is consisted of several optical pulses in different wavelength that are in the same WDM optical channel band as optical signal payload. A probable scheme to realize such optical switching as well as an optical switching node structure is proposed. A simplify principle experiment has proved the possibility of such switching method.
This paper presents the design and development of a bit rate transparent 3R O/E/O transponder, which accomplishes full data rate transparency from 30Mb/s to 2.5Gb/s by signal processing in electronic domain. With the use of chipsets that perform clock recovery in several continuous bit rate ranges, we develop a clock and data regenerating circuit self-adaptive to the bit rate of input signal. Experimental results presented in the last section of this paper show us that a good bit rate-adaptive capability and good BER performance can be achieved.
All-optical wavelength division multiplexing (WDM) networks using wavelength routing technology are considered to be a potential and practical solution to the next generation of wide area backbone networks. The ever-increasing demand for bandwidth further enhances the application of WDM optical networking technology. The main problem involved in design and optimization of wavelength-routed optical network is lightpath routing and wavelength assignment, namely, R&WA. In previous work on the R&WA problem, the project function has been analyzed by mathematic tools, such as integrate linear programming (ILP), heuristic algorithms or probability model, under the assumption of an ideal physical layer over which transmission impairments are ignored. In practical application, however, such impairments and their influence over traffic performance should be considered seriously, and the lightpath selection should be adjusted accordingly. In this paper, we propose an integrated approach for lightpath routing, which considers both the limitations of network topology and resource and the restrictions resulted from transmission impairments through the path computed by our heuristic algorithm when performing lightpath routing. The selected paths resulted from our proposed R&WA algorithm will be evaluated in a coarse-to-fine mechanism. By analyzing the impact of the optical devices (OXC, EDFA etc.) deployed through the lightpath, an optimal path is finally determined. This paper is composed mainly in three parts. For the first part, as to a given network topology, we present the ligthpath routing result, which investigate the influence of different network parameters, based on the proposed heuristic algorithm combining graph theory. For the second part, we studied the impact of various transmission impairments over BER performance, including crosstalk and noise caused by the optical devices. For the third part we combine the results obtained from the former two parts, and evaluate the selected path in a coarse-to-fine mechanism to make an optimal selection. The problem of load balancing is also briefly discussed in our paper.
This paper presents the design and development of a bit rate adaptive 3R O/E/O transponder, which accomplishes full data rate and protocol transparency from 30Mb/s to 2.5Gb/s by signal processing in electric domain. This transponder makes use of chipsets that perform clock recovery in continual bit rate ranges, that is, software configuration and provision are achieved for continual bit rates. The measuring results presented in this paper show us that a good bit rate-adaptive capability and a good BER performance can be achieved, which indicates the commercial application is feasible. This paper also discusses the architecture extension and application of this transponder toward an intelligent photoelectronic gateway for the future application in wide area optical networking. Transition from research laboratory into the marketplace is also undertaken now.
The basic technology of adaptive optical amplifier is introduced in this paper. How the performance of optical amplifier may meet the needs of application system is discussed according to the amplitude and shape of the input optical signal, the amplifier automatically adjusting the operating parameters. Taking the EDFA as an example, the feasibility to be realized technology of adaptive amplifier is investigated.
How to transport the control and management information of optical networking is a major concern these days. We compare several means and arrive at a conclusion that OSC (optical supervisory channel) is a better choice. The content of OSC is given and OSC channel wavelength, bit rate and coding method are discussed. An OSC example of WDM metro network are illuminated, which demonstrates the processing operation of overheads in OSC, FDI behavior for three types of failure, and Self-management of OSC subsystem. To fulfill the demand of intelligent and distributed management of optical transport network, an OSC of OC-3 (155Mbps) channel bit rate may be needed in the near future.