Majid Moghaddasi

OCDMA multi service with zero cross correlation code in free space optics

In this paper a variable weight code for Optical Code Division Multiple Access (OCDMA) is proposed to provide differentiated services in optical network. We call it multi service zero cross correlation (MS-ZCC) where it has zero-cross correlation. Using simulation, the performance of this code is compared with the conventional variable weight (VW)-ZCC code in free space optic (FSO) environment. The newly proposed code MS-ZCC shows an improvement of 300 meters link distance for weight 2 and 8, compared to VW-ZCC.

Physical Properties, Optical band gaps and Radiation Shielding Parameters Exploration for Dy3+-doped Alkali/Mixed Alkali Multicomponent Borate Glasses

Six compositions of 1 mol % Dy3+-doped multicomponent borate glasses containing single Li2O, Na2O, K2O and mixed Li2O–Na2O, Li2O–K2O, and Na2O–K2O oxides have been synthesized by well-known melt-quenching technique. Following the measured density and refractive index values, various physical parameters were estimated for all the glass samples and differences in them are correlated with structural changes. To explore optical properties like absorption edge (λcut-off), optical band gap energy (Eopt), and Urbach energy (ΔE), optical absorption spectra were recorded for all the glasses. The Eg has been calculated using Davis and Mott theory for direct allowed, and indirect allowed transitions and the results were reported. The Eg values are also estimated using absorption spectrum fitting (ASF) method. The optical parameters variations have also been associated with the structural changes occurring in the glasses with different alkali/mixed alkali oxides content presence. The shielding properties of the prepared glasses were studied in terms of effective atomic numbers (Zeff), mean free path (MFP), half value layer (HVL) and macroscopic effective removal cross-section (ΣR). From these results, it was found that Potassium (K) glass shows superior gamma ray shielding properties due to a higher value of Zeff and lower values of both MFP and HVL. These results indicate that the prepared glasses might be utilized in place of some common shielding materials to shield γ-rays and neutrons.

Investigation of circulation noise effect on SAC-OCDMA system with ring topology

In this paper, we investigate the performance of an OCDMA system with ring topology where number of the spans can be more than one. Effect of circulation noise is evaluated beside of shot noise and thermal noise. Through analytical approach, it is shown that higher amount of amplifier gain, produces higher amount of circulation noise. Also by increasing the number of nodes, the strength of the circulation noise is reduced and the ratio of this reduction is more for lower amplifier gain. For example, with increasing number of the nodes from 3 to 8, the amount of log variance of circulation noise increases only 1 unit (-13 to -14) for amplifier gain 20 dBm, while this value is 4 units (from -15 to -19) if gain is 10 dBm.