In this paper, the feasibility of a new vehicle axle detector for roadways based on fiber optic Mach-Zehnder interferometer was evaluated. This new vehicle axle detector used in this study has a relatively simple sensing principle. Thus the system can be composed of inexpensive and reliable components for the application to transportation system compared with the traditional vehicle axle detectors. The configuration and performance of the new vehicle axle detector was described. The process of conversion of the detected interferometer sensor signal into the weight of a vehicle axle was proposed. Simulating results show that the sensing response of the embedded fiber optic vehicle axle detector based on Mach-Zehnder interferometer can meet the requirements of a vehicle axle detector. In addition, a high-speed signal processing system was designed for the interferometer. The new vehicle axle detector has good potential as a basic sensor unit which can be widely used in ITS to detect the vehicle axle weight and identify the type of a vessel which passes over the detector.
In this paper, a Mo/Si multilayer mirror of normal incidence at E=60eV was firstly analyzed. From the measurement curves of a small angle x ray diffraction, the property of interfaces and the parameters including period thickness and roughness were gained. Through the analyzing, we found that performance is not good, the peak reflectivity is low and is not correspond with 60eV. Secondly, a revised design using Simulated Annealing arithmetic was applied in it. The revised design results shows a promising mirror at 60eV and are consistent with the results of the program of optical coating technology R&D center in Shanghai Institute of Optics and Fine Mechanics.
Under the constraints of the number of transceivers per node and wavelength continuity, the fairness issue of connections with different bandwidth granularities in survivable traffic-grooming WDM mesh networks is investigated. An extended wavelength-plane graph (EWG) model and two dynamic grooming path protection algorithms with considering blocking fairness are proposed. Based on dynamic traffic with different load, the performance of our schemes has been evaluated via simulations. The results show that they provide good blocking fairness while at the same time ensure a small increase in the overall traffic blocking probability.
This paper investigates the problem of dynamically establishing dependable connections in traffic-grooming wavelength division multiplexing (WDM) mesh networks, and proposes a dynamic shared sub-path protection (SSPP) scheme for multi-granularity traffic. To establish a dependable connection, SSPP searches a primary path for each connection request, and then it segments the found path into several equal-length sub-paths, and computes their corresponding backup paths, respectively. In SSPP, if two sub-paths are fiber-disjoint then their backup paths can share backup resources to obtain the optimal spare capacity. Based on dynamic traffic with different load, the performance of SSPP has been investigated via simulations. The results show that SSPP can make the tradeoffs between the resource utilization and the restoration time.
Efficiently grooming low-rate traffic flows into high-capacity lightpaths will improve the network throughput and resource utilization. In this paper, we study the traffic -grooming algorithm for WDM mesh networks. A novel dynamic grooming graph is proposed, which models the number of transceivers per node and the number of wavelength per fiber in addition to the combined information of IP layer and WDM layer, while taking into account the constraints of wavelength continuity in optical domain. Based on the grooming graph, a new dynamic traffic-grooming algorithm, namely Integrated Grooming Algorithm (IGA), is developed to provide an efficient solution to the traffic-grooming problem in WDM optical mesh networks. This algorithm is evaluated via simulations and results reveal that satisfactory performance of the proposed algorithms can be achieved.
The Shared Risk Link Groups (SRLG) concept is an extension of physical-disjoint, e.g. link/node-disjoint. It is defined as a group of links that share a common risk component whose failure can potentially cause the failure of all the links in the group. SRLG can be identified by a SRLG identifier. Different SRLG identifiers can be assigned to each link by network administrator in optical Traffic Engineering (TE) to satisfy connection's reliability requirement. A dependable connection can be achieved by establishing two SRLG-disjoint paths. A new dynamic integrated routing algorithm for shared path-protection based on SRLG-disjoint is presented in this paper. It provides the same level of protection against single SRLG failure as dedicated path-protection scheme. Moreover it is superior to dedicated path-protection scheme in network utilization. Network performance, based on dynamic traffic with different load, is investigated via simulations. The results show that the scheme can improve the performance of the network significantly.
In this paper, a priority-based wavelength assignment algorithm, Dynamic Threshold Method (DTM), is proposed. A set of wavelengths, Preferred Wavelength Set (PWS), is pre-allocated for each priority request. Based on the usage of wavelength in the PWS of a priority request, a threshold is dynamically calculated to decide whether the wavelengths for the higher priority request can be allocated to the lower. By using DTM, the blocking probability of the high priority request is guaranteed to be a lower degree, and at the same time performance of the low priority request is improved. So the network's average blocking probability is minimized. Simulation results of the network performance show that the proposed algorithm performs well in different dynamic traffic load situation.
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