The performance of LEO satellite optical networks varies with the satellite constellation. For simulating the performance of highly dynamic LEO satellite optical networks in different constellations quickly, this paper designs a constellation programmable large-scale LEO satellite optical network platform. The platform takes the parameters of the constellation and the change of inter-satellite link and ground-to-satellite link as input to build the dynamic network topology. For reducing the redundant storage of the link-state, the paper proposes a novel satellite network topology representation data structure, which combines the initial topology and the circular mapping linked list, to dynamically build topology that change over time. Based on the platform, we have conducted the performance evaluation of different constellations with different numbers of ground-to-satellite links. The simulation results show that the inclined orbit constellation cannot cover the polar regions of high latitudes, while in the area that can be covered by the constellation, there are more ground-to-satellite links in inclined orbit constellation.
Inside a service function chain (SFC), traffic flow follows a certain route, namely a service function path (SFP), to travel through each service function (SF) entity. A SFP consists of several end-to-end segments, whose source and destination are named anchor node (AN). SFs are located in multiple datacenters (DCs), and inter-DC light-paths need to be provisioned between separated SFs. In this paper, we introduce geography information of optical nodes and DCs, define special geographic distance between ANs in inter-DC elastic optical networks (EONs). Then following minimal geographic distance principle, we propose a geography-based SFP provisioning solution, which contains two heuristic algorithms, named geography-based shortest path and first-fit algorithm (GSP-FF) and geography-based k-shortest paths and first-fit algorithm (GK-FF). These algorithms can compress AN selection procedure extremely in fixed time, which cost little time for the AN selection of resource allocation. And benchmark algorithm use Dijkstra shortest path calculation and first-fit FS selection to allocate IT resources in DCs and FS resources in EONs. Then GSP-FF and GKFF are proposed to provision SFPs efficiently. In our simulation, we compare our proposed algorithms with benchmark algorithm deeply on blocking probability, running time, average hops, average geographic distance, et al. under different traffic load and other simulation environment. We also analyze the trend and reason for the performance difference among these algorithms. According detailed evaluation, simulation proves that the proposed algorithms in this paper could use geographic information efficiently, and achieve lower blocking probability with lower running time compared with the benchmark algorithm.
This paper presents the design and analysis of a novel resonant cavity enhanced photodetector which is realized by
utilizing concentric circular subwavelength gratings (CC-SWGs) as reflective mirrors. The CC-SWG proposed here can
achieve a reflectivity of higher than 99% within a broad wavelength range from 1.37 to 1.63 μm. The calculated peak
quantum efficiency of the designed photodetector can achieve 90% at 1.55 μm.
Analysis of light field distribution within a dual-absorption RCE p-i-n photodetector has been
performed. A formula for the field distribution inside the cavity is derived. This formula is derived from
the continuity equations, and employed to evaluate the frequency response of the dual-absorption RCE
photodetector. This photodetector has been optimized for high-speed applications. The optimized
structure shows a 3dB bandwidth of 20 GB with intrinsic absorption region to be 400nm, as well as
effective illumination area and peak quantum efficiency to be 900 μm2 and 92%, respectively.
N-doped GaAs nanowires (NWs) were grown on GaAs (111) B substrate by means of vapor-liquid-solid (VLS)
mechanism in a metalorganic chemical vapor deposition (MOCVD) system. Two flux rates of n-type dopants used for
GaAs NWs growth were researched. For comparison, undoped GaAs NWs were grown at the same conditions. It is
found that all NWs are vertical to the substrate and no lateral growth occurs. The growth rate is proportional the flux
rates of n dopant. It is observed that there is Gibbs-Thomson effect in doped NWs. Pure zinc blende structures without
any stacking faults from bottom to top for all three samples were achieved.
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