Priority-based parameter optimization strategy for reducing the effects of four-wave mixing on WDM system

In order to meet the ultra high speed and ultra long-haul transmission distance in wavelength division multiplexing (WDM) systems, the nonlinear impairment affecting the overall spectral efficiency and system performance should be minimized. This paper proposes a strategy to mitigate the four-wave mixing (FWM) effect in WDM system. The strategy determines the effect of both single and combined effects of second, third, and fourth optimization priority parameters such as fiber length, input power, dispersion, channel spacing, and effective area on FWM power. A comparison study was made under different types of optical fiber such as single-mode fiber (SMF), dispersion shifted fiber, non-zero dispersion fiber, and non-zero dispersion shifted fiber. In addition, the system performance in term of bit-error-rate was calculated in the case of single priority (impact of effective area) and combined priority (impact of effective area, input power, fiber length and channel spacing). The results show that the FWM effect was reduced based on the transmission parameters order of optimization, i.e., priority selection proposed. Moreover, the results indicated that increasing sequentially the effective area, fiber length; channel spacing and decreasing the input power provide the most significant sequence in suppressing the effects of FWM. This priority sequence brought the suppression ratio to approximately 26.3% in SMF, which suppressed the FWM effects up to −50 dBm. In term of BER; the combined priority introduces improvement in BER of 2.31 × 10⁻²⁵ in comparison with single priority that has value of BER 4 × 10⁻¹⁴. Finally, this work suggests that the proposed priority-based parameter optimization strategy is an ideal solution for optimum performance of WDM system.     

Coulomb dissociation of incident 16O at 4.5 GeV/c

Projectile multifragment breakup of ¹⁶O, ²C and ⁷Li at energies 3.0–4.5 A-GeV is studied by means of the Weizsäcker-Williams method. The fragmentation channels of the ¹⁶O projectile at 4.5 A-GeV are investigated and compared with that of ¹⁶O at 200 A-GeV. The events characterized by N _h=0 and the events due to both Coulomb and diffraction dissociation have been selected and analyzed as a function of impact parameter. Also, the dependence of the electromagnetic dissociation cross-section on incident energy and the charge of projectile and target is found.     

Structural and electrical characterization of SxSe100−x thin films

Thin films of samples of the glassy S_xSe_100−x system with 0 ≤ x ≤ 7.28 have been prepared by thermal evaporation technique at room temperature (300 K). X-ray investigations show that the structure of pure selenium (Se) does change seriously by the addition of small amount of sulphur S ≤7.28%. The lattice parameters were determined as a function of sulphur content. Results of differential thermal analysis (DTA) of the glassy compositions of the system S_xSe_100−x were discussed. The characteristic temperatures (T_g, T_c and T_m) were evaluated. Dark electrical resistivities, ρ, of S_xSe_100−x thin films with different thicknesses from 100 to 500 nm, were measured in the temperature range from 300 to 423 K. Two distinct linear parts with different activation energies were observed. The variation of electrical resistivity of examined compositions has been discussed as a function of the film thickness, temperature and the sulphur content. The application of Mott model for the phonon assisted hopping of small polarons gave the same two activation energies obtained from the resistivity temperature calculations.     

Vermiculite as an exchanger for copper(II) and Cr(III) ions,kinetic studies

The adsorption of Cu(II) and Cr(III) ions by pure clay mineral, vermiculite, was examined in aqueous solution with respect to the adsorbent dose, initial metal ion concentration, pH, and contact time. The studies showed that vermiculite can be used as an adsorbent material for the moderate removal of Cr(III) and Cu(II) from aqueous solutions. Lagergren first-order, pseudo-second-order, and intraparticle diffusion models were used to describe the kinetic data. The kinetics of adsorption indicates that the process fitted well the intraparticle diffusion model.     

A Suitable Active Control for Suppression the Vibrations of a Cantilever Beam

In our consideration, a comparison between four different types of controllers for suppression the vibrations of the cantilever beam excited by an external force is carried out. Those four types are the linear velocity feedback control, the cubic velocity feedback control, the non-linear saturation controller (NSC) and the positive position feedback (PPF) controller. The suitable type is the PPF controller for suppression the vibrations of the cantilever beam. The approximate solution obtained up to the first approximation by using the multiple scale method. The PPF controller effectiveness is studied on the system. We used frequency-response equations to investigate the stability of a cantilever beam. We notified that, there is a good agreement between the analytical solution and the numerical solution.     

LINEAR AMPLIFIER VIA THE SQUEEZED COHERENT STATES SUPERPOSITIONS

Much attention is given for the squeezed coherent states (SCS's) superposition. The s-parameterized charactristic function (CF) for the output field with the superposition of SCS's as input field is given. The s-parameterized quasiprobabilty distribution function (QDF) for the output field with superposition of SCS's as input state are investigated. Various moments are calculated by using the s-parameterized CF for that field. The Glauber second-order coherence function is calculated. The quadrature squeezing for the output field are discussed. Some QDF's of the output fields are plotted as functions of the interaction time. Phase properties of the superpostion of SCS's are studied. The s-parameterized phase distributions obtained by integrating the s-parameterized QDF over radial variable are illustrated.     

Growth of Fe-doped ZnO nanorods using aerosol-assisted chemical vapour deposition via in situ doping

In situ Fe doping of ZnO nanorods (NRs) was performed using aerosol assisted chemical vapour deposition (AA-CVD) technique. As the aerosol generator is located outside the reactor, AA-CVD provides the flexibility to control doping parameters, such as doping timing, doping duration and a wider choice of dopant precursors. The Fe dopant aerosol was flowed into the reactor during the growth of ZnO NRs to achieve in situ doping. The X-ray diffraction analysis indicates that the Fe dopants were introduced into the ZnO lattice and present mainly in the form of Fe²⁺. This result is supported by the X-ray photoelectron spectroscopy analysis as the doublet separation is 13.6 eV, although there is a shift of Fe_1/2 and Fe_3/2 peaks to a lower binding energy levels. A strong green emission of PL of Fe-doped ZnO NRs shows that the NRs have poor crystal quality attributed to the Fe-induced defects (recombination centres). The poor photocatalytic performance in degrading Rhodamine B solution of Fe-doped ZnO NRs further proves that the Fe-induced defects were recombination centres rather than traps. Lastly, the growth mechanism of in situ Fe doping of ZnO NRs was discussed.     

Erbium in silicon–germanium quantum wells

Strained Si_1−xGe_x/Si quantum wells have been doped with erbium by implantation. A comparison is made with strained Si_1−xGe_x/Si quantum wells and relaxed Si_1−xGe_x, with x between 10% and 25%, doped with erbium during MBE growth. The erbium concentration was between 1×10¹⁸ and 5×10¹⁸ cm⁻³ throughout the active regions. Transmission electron microscopy, X-ray diffraction, and photoluminescence studies indicate that good regrowth can been achieved after full amorphisation by implantation of the strained quantum wells. The erbium luminescence is more intense in the Si_1−xGe_x/Si layers, but erbium-implanted samples containing Si_1−xGe_x exhibit defect luminescence in the region of 0.9–1.0 eV. These defects are also present when Si_1−xGe_x/Si quantum wells are implanted with an amorphising dose of silicon, and then regrown. They are attributed to small germanium-rich platelets, rather than to erbium-related defects. Electroluminescence is presented from a forward biased erbium-implanted Si_0.87Ge_0.13/Si structure at a drive current density of only 1.8 mA/cm².