With the recent explosive growth of Internet traffic, optical networks with high
connectivity and large capacity are indispensable. This can be achieved by
multi-dimensional optical routing networks, which can offer fine bandwidth granularity
and a large number of channels. In this paper, a trunk switched model is used to study the performance of multi-dimensional optical routing networks. The
closed-form network utilization is derived and compared to that of one-dimensional
optical routing networks. The network utilization gain is found to be closely
related to the link correlation and be insensitive to the network size. Besides,
based on this analytical model, the closed-form conversion gains are derived for
both partially and fully convertible cases. These results provide crucial
information in performance optimization of multi-dimensional optical routing networks.
Recent advances in optical devices greatly enhance the feasibility of optical code-division multiplexing/wavelength-division multiplexing (CDM/WDM) network. In this paper, the performance in blocking probability in a two-dimension code/wavelength routing network is investigated. Facilitated by the optical code and wavelength conversion, the capability in reconfigurability, restoration and protection of the optical layer is enhanced. The network blocking performances under various conversion capabilities are investigated and the blocking probabilities are given in closed-form expressions. Under certain conditions, the analysis of the two-dimension routing network can be extended to N-dimension routing network by iterative decomposition procedure. Numerical results are obtained to show the performance improvement from the optical code conversion in terms of code conversion gain. With wavelength conversion provided in the network, the addition of the code conversion achieves a conversion gain as high as 104 even when the code conversion is provided with a low placement density of 0.2.
The potential development of optoelectronic devices based on the NLO response of organic molecules has aroused much recent interest. The influence of the molecular interactions on their NLO properties is important to both basic and application study. The dye rhodamine B can form different protonation and aggregation states by changing the bulk pH, which is revealed by the UV-visible absorption spectra and the fluorescence emissions spectra. Here we also use the hyper-Rayleigh scattering (HRS) technique to probe more detailed information about the protonated forms and aggregates. Because rhodamine dye is an ionic compound, the classical technique electric-field-induced second-harmonic generation can not be used to get the first-order hyperpolarizability (beta) . Our further studies show that rhodamine has strong multi-photon fluorescence emission under the radiation of 1064nm and it overlaps the HRS signal at 532 nm. The concentration dependence of the HRS intensity shows that only in the very low concentration range the HRS signal increases linearly with the increasing concentration. In the higher range, the signal deviates from the line on the below side, which may arise for the linear absorption of the signal at 532 nm, nonlinear absorption of the incident laser beam, the intermolecular effect and distortion of the incident laser at high concentration.
Large third-order susceptibilities, (chi) (3) or (gamma) , have been observed for II-VI semiconductor nanoparticles. However, there are only few studies on the second-order susceptibilities because it is usually believed that the centrosymmetry or near-centrosymmetry of the particles eliminate the (beta) to zero or very small vale, Here the Hyper-Rayleigh scattering (HRS) technique is used to measure the second-order NLO response of nanoscale CdS Colloids with different surfaces in solution, which are denoted by CdS/Cd2+, CdS/S2-, CdS/SC(NH2)2 CdS/AOT- and CdS/Py. The result shows that the 'per particle' (beta) values for CdS nanoparticles are very large. And the (beta) values are different for CdS nanoparticles with different surfaces. Time dependent experiment show that the HRS signal deceases remarkably as time goes by. Further studies reveal that it has mutli-photon fluorescence (MPF) emission under the radiation of 1064 nm for newly made samples, but for aged stable sample the MPF is rather weak. All these experiments show that the HRS and MPF signals are very sensitive to the changes of the nanoparticle surface or the nanoparticle/solution interface. They also give the evidences proving that the surface termination of the crystalline lattice that creates a condition of non- centrosymmetry is contributing to the large (beta) values for CdS nanoparticles.
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