Novel virtual user scheme to increase data confidentiality against eavesdropping in OCDMA network

We propose a novel technique to increase the confidentiality of an optical code division multiple access(OCDMA) system.A virtual user technique is analyzed and implemented to make an OCDMA system secure.Using this technique,an eavesdropper will never find an isolated authorized user’s signal.When authorized users and virtual users transmit data synchronously and asynchronously,network security increases by 25% and 37.5%,respectively.     

Combined Path and Maximum Empty Static Routing Algorithms with Wavelength Assignment for Future Transport Networks

Abstract

In this article, two static routing algorithms have been proposed and compared to some of the existing algorithms on the basis of blocking probability. The two proposed static routing and wavelength assignment algorithms reduce the blocking probability to maximize the utilization of the network. All of these algorithms are analyzed and compared with four wavelength assignment schemes, which are first-fit, random, most used, and least used. It is shown that our proposed static algorithms give the best performance for first-fit wavelength assignment and most used wavelength assignment strategies with reduced complexity. For least used wavelength assignment and random wavelength assignment, 1 fixed and 2 alternate routing algorithm gives the lowest blocking probability.     

Approximate and Exact Small Signal Analysis for Single-Mode Fiber Near Zero Dispersion Wavelength with Higher Order Dispersion

This article presents the comparison of approximate and exact small-signal theories for analyzing the influence of the higher-order dispersion terms on dispersive optical communication systems operating near zero dispersion wavelength for linear single-mode fiber. For the approximate theory, the generalized conversion matrix has been reported and gives the transfer function of intensity and phase from the fiber input to fiber output for a laser source including the influence of any higher-order dispersion term. In addition, expressions for the small-signal frequency response and the relative intensity noise (RIN) response of an ultrafast laser diode including noises are derived. However, it is observed that the approximation assumed for the second-order dispersion term for the approximate analysis is not valid. From the approximate theory, the exact generalized conversion matrix and exact expressions for small-signal frequency response and relative intensity noise (RIN) are obtained. We show that for the exact theory, the second-order dispersion term has no effect on intensity and frequency response even at large modulating frequencies and large propagation distances contrary to the approximate theory as reported by other authors. But we show that third-order dispersion term certainly has some minute impact on the frequency and RIN response for long distance links at high modulating frequencies.     

Characterization of nanostructured hollow polymer spheres with small-angle neutron scattering (SANS)

Hollow polymer spheres synthesized from a vesicle-directed polymerization can be dried and redispersed in water using a variety of nonionic ethoxylated alcohol surfactants as stabilizers. The final dispersions consist of both polymer shells and surfactant micelles, which remain together in colloidal suspension for at least several months. Small-angle neutron scattering (SANS) is used to measure the polymer shell thickness (63 A) and core radius (560 A) of the surfactant-stabilized hollow polymer spheres in the presence of surfactant micelles. Characterization by SANS provides information about the surfactant bilayer and polymer shell thicknesses which were previously unattainable.     

Theory of Frequency-Dependent Polarization of General Planar Electrodes with Zeta Potentials of Arbitrary Magnitude in Ionic Media: 2. Applications and Results from Homogeneous and Array Systems of Electrodes

The expressions obtained in the previous paper for electrode polarization are applied to a homogeneous planar electrode and a planar array of electrodes used in the generation of nonuniform fields. The effective far field experienced outside the double layer is computed for both electrodes, and sample spectra are provided. The effective far field expression contains the electrode impedance and the effects of concentration polarization due to the static double layer on the electrode generated by the ζ potential. The effective far field results are compact and contain simple integrals that can be evaluated numerically.     

Multi parameter optimization of Raman Fiber Amplifier using genetic algorithm for S band dense wavelength division multiplexed system

A simple genetic algorithm is implemented to perform multi parameter optimization of Raman Fiber Amplifier for 100 channel S band dense wavelength division multiplexed system at 25 GHz interval. A cost effective system using single Raman pump is investigated aiming at maximum average gain. The single counter propagating pump is optimized to frequency of 211.528 THz and 652.93 mW power level with optimum Raman fiber length of 44.064 Km. There is evidence to show that the optimum solution presents a small gain variation (less than 3 dB) over an effective bandwidth covering 197–199.475 THz. The optimized configuration enabled an adequate system performance in terms of acceptable Q-factor (19.52 dB) and BER (1.46 × 10⁻²¹).     

Performance Evaluation and Characterization of Hybrid Optical Amplifiers for Dwdm Systems at Ultra Narrow Channel Spacing

We study hybrid optical amplifiers (HOAs) for dense wavelength division multiplexed (DWDM) systems at reduced channel spacing (<0.2 nm). The Raman erbium-doped fiber amplifier (EDFA) (R-E) and EDFA-semiconductor optical amplifier (SOA) (E-S) hybrid optical amplifiers (HOAs) are investigated for the first time at 0.05 and 0.1 nm of the channel spacing. We show that the R-E HOA provides better gain (23.9 dB) and induces lesser crosstalk (-14.1 dB) with minimum utilization of the bandwidth. We report that 70 km is the optimum span distance at which the R-E HOA achieves a 2450 km transmission distance with acceptable performance. The theoretical results are found to be in accordance with numerical simulations in terms of the amplifier gain and induced crosstalk.     

Theory of Frequency-Dependent Polarization of General Planar Electrodes with Zeta Potentials of Arbitrary Magnitude in Ionic Media

Electrode polarization effects have long aggravated the efforts of low frequency analysis, particularly those investigations carried out on biological material or in highly conductive media. Beginning from elementary equations of electrostatics and hydrodynamics, a comprehensive model is devised to account for the screening of a general planar electrode by an ionic double layer. The surface geometry of the planar electrode is left unspecified to include any type of micromachined array. Building on the previous work by DeLacey and White (1982, J. Chem. Soc. Faraday Trans. 2 78, 457) using a variational theorem, we extend their numerical results with compact analytic solutions, analogous to the Debye-Hückel potential for dc systems, but applicable now to dynamic ac experiments. The variational approach generates functions that are not restricted by perturbation expansions or numerical convergence, representing optimal approximations to the exact solutions. Copyright 2000 Academic Press.     

Cryo-TEM studies of worm-like micellar solutions

Solutions of worm-like micelles display a rich rheological behavior that makes them useful as, for example, drag-reducing agents or viscosity enhancers. The properties of these solutions depend on the morphology and interactions between the micelles, both of which can be tuned by changing solution conditions. Although there has been extensive theoretical study of these solutions, there are often conflicting explanations, or no explanation, of an observed trend. Application of cryogenic transmission electron microscopy (cryo-TEM) for the direct visualization of the micelles can help correlate microstructure to rheology. Of particular interest is the cause of a maximum in viscosity as a function of increasing surfactant or salt concentration. Several studies support the theory of a transition from linear to branched micelles, while other studies report no change in microstructure or no connection between structure evolution and changes in viscosity. More systematic and thorough studies that combine cryo-TEM with other experimental techniques are needed.     

A novel optical burst switching architecture for high speed networks

A novel optical burst switching （OBS） high speed network architecture has been proposed. To verify its feasibility and evaluate its performance, just-enough-time （JET） signaling has been considered as a high performance protocol. In the proposed architecture, to avoid burst losses, firstly, a short-prior- confirmation-packet （SPCP） is sent over the control channel that simulates the events that the actual packet will experience. Once SPCP detects a drop at any of the intermediate nodes, the actual packet is not sent but the process repeats. In order to increase network utilization, cost effectiveness and to overcome some limitations of conventional OBS, inherent codes （e.g., orthogonal optical codes （OOC））, which are codified only in intensity, has been used. Through simulations, it shows that a decrease in burst loss probability, cost effectiveness and a gain in processing time are obtained when optical label processing is used as compared with electronic processing.