Hybrid waveband/wavelength switching in intelligent optical networks is gaining more and more academic attention. It
is very challenging to develop efficient algorithms to efficiently use waveband switching capability. In this paper, we
propose a novel cross-layer routing algorithm, waveband layered graph routing algorithm (WBLGR), in waveband
switching-enabled optical networks. Through extensive simulation WBLGR algorithm can significantly improve the
performance in terms of reduced call blocking probability.
Checking the great generator's vibration online is difficult because of its strong electric and magnetic field so it needs had better no metal in the sensor. We introduce a method of measuring vibration by using FBG and demodulating it by blazed grating and it doesn't use any metal. We present the design method and the theory of
demodulation. The results of the experiment show that the vibration amplitude of the exciter matches the detected signal under the stable frequency. The experiment also successfully separated the temperature shift and vibration signal.
Giving a new method to tuning a fiber Bragg grating into a chirped grating using a gradient curvature beam. Stick a FBG to an "S" shape beam with one end free and another give a pull. The curvature of the beam would change and the FBG get gradient strain. Thus we get the chirped grating while the central wavelength doesn't change. The design method and the theoretical analysis are given. The maximum chirped bandwidth in our experiment is 5.10nm and the central wavelength does not change.
A novel waveband switching node architecture is proposed using tunable optic filters for arbitrary waveband add/drop. The simulation results show this new architecture achieves lower blocking probability and reduce the scale of ports at switch fabric.
A novel hybrid WDM/TDM optical access network architecture called wavelength shared WDM PON and its media access control mode is proposed. The system is based on a two-stage distribution tree connecting OLT and ONUs.and uses ALOHA protocol for control channel and FIFO scheduler to efficiently assign bandwidth. The packet delay in the system is analyzed and the numerical results demonstrate that the system possesses well performance of packet delay.
In this paper, the guideline of wavelength assignment for WDM distribution networks is studied and a novel wavelength assignment algorithm is proposed. The numerical and simulations results demonstrate that this algorithm can improve the system's performance.
Waveband switching routing is a new problem for research community. It is has some different with the routing of wavelength assign problem. In this paper, we propose a new ideal for agent based Waveband switching network construction. Primary simulation shows that in this way complexity of virtual network topology and blocking probability reduced.
In this paper a novel hybrid WDM/TDM optical access network architecture and its media access control (MAC) alogrithm is proposed. Extensive simulations are conducted and the results show that the algorithm can provide determinate delay bound for each flow, possesses throughput fairness and decreases the packet delay of low
Recently, TCP performance over Optical Burst-Switched Networks (OBSN) has drawn more and more attention, but most of previous work were based on small linear network under static traffic, which was much different from the real condition. In this paper, a more realistic OBSN model was set up and dynamic TCP performance over it was investigated with the help of a <i>ns</i>2-based OBSN simulation platform. The impacts of OBSN configuration parameters and different TCP implementations on the overall throughput were discussed.
In this paper, we proposed two waveband switching algorithms: Minimal Hop Routing (MHP) and Maximal Overlapped Routing (MOP). The differences between them are the weight of link in the layered graph at the waveband and wavelength planes. In MHP algorithm, the weight of links at waveband and wavelength planes are the same, but MOP assigns lower weight to them at the waveband plane than that at the wavelength plane. We conducted extensive simulations with dynamic traffic patterns in the mesh network topology. We evaluated the performance of the proposed algorithms in terms of blocking probability and the number of OXCs port with waveband algorithms of MOP, MHP and RWA algorithm of shortest path routing (SPR). Simulation result shows that waveband algorithm has low blocking probability, and less number of ports is used.
In this paper, a traffic-grooming problem for multi-granularity traffic of SDH/SONET in WDM grooming mesh networks is investigated. Our objective is to improve the throughput of SDH/SONET WDM mesh networks. We propose a heuristics algorithm to solve this problem. The performances of this traffic grooming heuristics algorithm are evaluated in WDM grooming networks. Finally, we presented and compared the simulation results of this methodology in dynamic traffic grooming WDM mesh networks with that of other methodologies.
Utilizing optical technologies for the design of packet switches and routers offers several advantages in terms of scal-ability, high bandwidth, power consumption, and cost. However, the configuration delays of optical crossbars are much longer than that of electronic counterpart, which makes the conventional slot-by-slot scheduling methods no longer be-ing the feasible solutions. Therefore, there must find some tradeoff between the empty time slots and configuration overhead. This paper classifies such scheduling problems into preemptive and non-preemptive scenarios, each has its own advantages and disadvantages, and decides whether the traffic in one input queue should be completely transmitted in one switch configuration. Although non-preemptive scheduling is inherently not good at achieving above-mentioned tradeoff, it is shown, however, that the proposed maximum weight matching (MWM) based greedy algorithm is guaranteed to achieve an approximation 2 for arbitrary configuration delay, and with a relatively low time complexity O(N2). For preemptive scheduling, a novel 2-approximation heuristic is presented. Each time in finding a switch configuration, the 2-approximation heuristic guarantees the covering cost of the remaining traffic matrix to have 2-approximation. Simulation results demonstrate that 2-approximation heuristic (1) performs close to the optimal scheduling; (2) outper-forms ADJUST and DOUBLE in terms of traffic transmission delay and time complexity.
In this paper, we propose a novel modified architecture of Optical Burst-Switched Networks, called <i>Reliable Optical Burst Switching</i> (ROBS), which introduces congestion control and retransmission mechanisms of TCP to OBS layer. Design scheme of edge and core nodes for ROBS are both demonstrated. Part of the ROBS function has been implemented on <i>ns</i>-2 platform. Performance improvements due to burst retransmission are simulated and presented.
Proc. SPIE. 5596, Optical Transmission Systems and Equipment for WDM Networking III
KEYWORDS: Logic, Data modeling, Data transmission, Computer simulations, Picosecond phenomena, Optical networks, Fluorescence correlation spectroscopy, Local area networks, Broadband telecommunications, Standards development
In IEEE 802.17 draft standard, bridging technique is suggested to connect multiple resilient packet rings (RPRs). However, we demonstrate that bridging technology may not be a feasible solution because too much of resources and overhead would be occupied or needed to transmit packets across multiple RPR sub-networks. To construct interconnected RPRs and thus solve bridging related issues, this paper introduces a new kind of RPR nodes, namely, RPR-X nodes, to interconnect multiple RPR sub-networks. In our solutions, standard RPR frame defined by IEEE 802.17 is used to transmit packets on the local RPR sub-network, the extended RPR frame (i.e., cross frame) is used to transmit the packets across different RPR sub-networks. For RPR-X node, it can identify and process both standard RPR frame and extended RPR frame. While for RPR-S node (standard RPR node), it can only identify and process standard RPR frame. Based on the extended definitions of standard RPR frame, we give a detailed design of MAC layer reference model of RPR-X node, and propose an original packet cross forwarding algorithm, with a view to transmitting the packets across multiple RPR sub-networks, and at the same time to guaranteeing the cross forwarding algorithm to be compatible with the standard forwarding procedure of RPR-S node. Theoretical analysis and simulation results demonstrate that the proposed methods perform well in terms of performance metrics such as network's throughput and end-to-end delay.
Based on the scenario that the number of wavelengths may be fixed by upgrading the WDM metro ring networks, this paper proposes a novel WDM slotted-ring architecture with nodes employing one fixed transmitter and a set of fixed receivers. It presents a detailed design and analysis of node architecture and MAC protocol, which aim at guaranteeing fairness to each node and achieving efficient bandwidth utilization. The main advantages of this proposed node architecture and its corresponding MAC protocol can be summarized as: 1) Electronic buffer and process delays can be minimized as the packets will not be processed until they arrive at the destination nodes. 2) No contention will occur at the destination nodes. 3) No tunable components used. 4) No dedicated control channel used to transfer the packets. 5) Packets can be stripped by both destination and source nodes, and there is no need to perform O-E-O conversions. It is shown through theoretical analysis and simulation results how the proposed architecture and MAC protocol can achieve a good throughput, low queuing delay and reasonable packet loss probability. In the case of a large number of wavelengths, or if the number of wavelengths increases by upgrading the networks, this paper further proposes an original design method: employing one fixed transmitter and a set of tunable receivers that can only be tuned among partial continuous wavelengths, we show this method can achieve a good trade-off in terms of performance metrics such as network’s throughput, cost and implementing complexity.