Crosstalk and Signal Integrity in Ring Resonator Based Optical Add/Drop Multiplexers for Wavelength-Division-Multiplexing Networks

With 400 Gbps Ethernet being developed at the time of writing this thesis, all-optical networks are a solution to the increased bandwidth requirements of data communication allowing architectures to become increasingly integrated. High density integration of optical components leads to potential ‘Optical/Photonic’ electromagnetic compatibility (EMC) and signal integrity (SI) issues due to the close proximity of optical components and waveguides. Optical EMC issues are due to backscatter, crosstalk, stray light, and substrate modes. This thesis has focused on the crosstalk in Optical Add/Drop Multiplexers (OADMs) as an EMC problem. The main research question is: “How can signal integrity be improved and crosstalk effects mitigated in small-sized OADMs in order to enhance the optical EMC in all-optical networks and contribute to the increase in integration scalability?” To answer this question, increasing the crosstalk suppression bandwidth rather than maximizing the crosstalk suppression ratio is proposed in ring resonator based OADMs. Ring resonators have a small ‘real estate’ requirement and are, therefore, potentially useful for large scale integrated optical systems. A number of approaches such as over-coupled rings, vertically-coupled rings and rings with random and periodic roughness are adopted to effectively reduce the crosstalk between 10 Gbps modulated channels in OADMs. An electromagnetic simulation-driven optimization technique is proposed and used to optimize filter performance of vertically coupled single ring OADMs. A novel approach to analyse and exploit semi-periodic sidewall roughness in silicon waveguides is proposed. Grating-assisted ring resonator design is presented and optimized to increase the crosstalk suppression bandwidth

Comparison between Three Off-Grid Hybrid Systems (Solar Photovoltaic, Diesel Generator and Battery Storage System) for Electrification for Gwakwani Village, South Africa

A single energy-based technology has been the traditional approach to supplying basic energy needs, but its limitations give rise to other viable options. Renewable off-grid electricity supply is one alternative that has gained attention, especially with areas lacking a grid system. The aim of this paper is to present an optimal hybrid energy system to meet the electrical demand in a reliable and sustainable manner for an off-grid remote village, Gwakwani, in South Africa. Three off-grid systems have been proposed: (i) Photovoltaic (PV) systems with a diesel generator; (ii) Photovoltaic systems and battery storage; and (iii) Photovoltaic systems with diesel generator and battery storage. For this analysis, different size of photovoltaic panels were tested and the optimal size in each scenario was chosen. These PV sizes were 1, 0.8, 0.6 and 0.4 kW. The optimization between these sizes was built based on three main objectives. These objectives are: (i) energy demand satisfaction; (ii) system cost; and (iii) pollution. For the first and second system scenarios, the optimal size was the 1 kW with battery and 1 kW with diesel generator; the third scenario results did not sufficiently match the three objectives. A general comparison has been carried out between the two optimal systems when the diesel generator is used and when the battery is applied. Both scenarios can sufficiently meet the demand without any considerable interruption, but disparities exist between them in relation to cost and technical optimization. There is a huge difference in the cost between these scenarios. The total cost in PV-Battery system (Scenario 1) represents only 26% of the entire PV system. Also, the PV and Battery system does not release any harmful emissions compared with nearly 6 tCO2/year in the PV with Diesel system (Scenario 2). Also, Scenario (3) is a viable option in terms of energy production but costs more and is proposed to be more beneficial using an economies-of-scale analysis

Numerical modelling of surface plasmonic polaritons

Extending optoelectronics into the nano-regime seems problematic due to the relatively long wavelengths of light. The conversion of light into plasmons is a possible way to overcome this problem. Plasmon’s wavelengths are much shorter than that of light which enables the propagation of signals in small size components. In this paper, a 3D simulation of surface plasmon polariton (SPP) excitation is performed. The Finite integration technique was used to solve Maxwell’s equations in the dielectric-metal interface. The results show how the surface plasmon polariton was generated at the grating assisted dielectric-metal interface. SPP is a good candidate for signal confinement in small size optoelectronics which allow high density optical integrated circuits in all optical networks. Keywords: All-optical networks, Optical integrated circuits, Optoelectronics, Plasmons, Surface plasmon polarito

Modelling of asymmetric channel plasmonic polariton waveguides

Abstract Channel plasmonic polariton (CPP) waveguides are a promising technology for integrated photonics. They offer several advantages over other plasmonic waveguides and are well-suited for various applications. In this research, a new design of asymmetric double-trenched CPP waveguide is suggested and examined. This design consists of two silicon trenches etched into a silicon dioxide substrate layer; with a gold layer sandwiched in between. The trenches are asymmetric, with one trench being wider than the other. This asymmetry creates a spatially varying surface plasmon polariton (SPP) field, which can guide light along the waveguide. The polarization characteristics of this proposed design are analyzed over a specific wavelength range (0.7 $$-$$ - 1.7 µm) to evaluate the mode confinement of the light within the structure. The design performance was optimized by changing the gold layer thickness and the dimensions of the lower trench. Different scenarios are examined to observe TE and TM-polarized modes’ behavior within the groove. A 1867.119 dB/µm suppression level at 0.92 µm wavelength is achieved which offers a small-size component for compact photonic logic gates, enabling the development of next-generation photonic devices

An Approach for Solving Missing Values in Data Set Using Clustering-Curve Fitting Technique

Missing values in data sets represent one of the greatest challenge in analyzing data to extract knowledge from the data set. The work in this paper presents a new approach for solving the missing values problems by using and merging two different techniques; clustering (K-means and Expectation Maximization) and curve fitting. More than twenty thousand records of real health data set collected from different Iraqi hospitals were used to create and test the proposed approach that showed better results than the most popular techniques for estimation missing values such as most common values, overall overage, class average, and class most common values. Different software were used in the proposed work including WEKA (Waikato Environment for Knowledge Analysis), Matlab, Excel and C++

Over Coupled Ring Resonator Based Add/Drop Filters

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The performance of add/drop filters based on over-coupled ring resonators is analysed and simulated. Over coupling improves the performance of the filters by providing a wider bandwidth over which high crosstalk suppression is achieved. Inter-band and intra-band crosstalk associated with Wavelength Division Multiplexing (WDM) in optical filters are examined as a function of coupling coefficients. The simulation results show that, in over coupled double ring resonators, the crosstalk suppression bandwidth is increased in comparison with that of critically-coupled ring resonators. Increased bandwidth will allow such filters to be used for higher data rate signls, and moreover, for different modulation techniques (such as return to zero RZ and non-return to zero NRZ)

Vaccination Status and Seroprevalence of Hepatitis B Surface Antigen Among Health Care Workers in Taiz, Yemen Republic

Background: Exposure to Hepatitis B virus (HBV) infection is one of the most common occupational diseases among the providers of the health care services. During the course of their clinical work; Health Care Workers (HCWs) are at risk of acquitting HBV infection or transmitting it to their patients. Vaccination for medical personnel against HBV  in Yemen Republic is recommended but not strictly enforced. Detection of the viral hepatitis B surface antigens (HBsAg) is one of the accurate and cheap methods to assess HBV prevalence. This method is used in this study to assess HBV prevalence among HCWs in Taiz; to in order to improve on methods of interventions to control this infection among them. Objectives: The objective of this study was to assess the vaccination status and the seroprevalence of HBsAg among HCWs in Taiz; Yemen republic.  Methods: This cross sectional study was conducted through the period between January and March, 2018, and from April and July, 2019, in the part of Taiz City; Yemen Republic belonging to legitimate authorities. 362 HCWs were included in this study and are selected through repeated casual visits to hospitals and medical centers. A questioner was made to get information on the participants' characteristics and their vaccination status, medical hestory and risk factors for HBV transmission. Five ml venous blood was then collected from every participant to assess HBsAg. Results: the overall vaccination percentage was 21.54% (27.5% in male and 17.9% of female). The seroprevalence of HBsAg was 2.76%, all vaccinated participants were HBsAg negative. Needle stick and sharp object injury was an important risk factor of HBV infection

Estimation of the Bandwidth of Acceptable Crosstalk of Parallel Coupled Ring Resonator Add/Drop Filters

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.In this paper, a parallel coupled optical ring resonator filter is studied and the transfer function is derived using the Signal Flow Graph approach to identify the filter performance in terms of crosstalk suppression bandwidth and signal integrity. This paper proposes the use of the Signal Flow Graph (Mason’s rule) approach to determining the filtering characteristics of ring resonators. A commercial electromagnetic simulator is used to validate the analytical model. The modelling of the parallel coupled ring resonator covers the analysis of the out-of-band rejection ratio, crosstalk suppression, loss effect and the effect of coupling coefficients on the crosstalk bandwidth. The good agreement between analytical model results and simulation results suggest that using the derived analytical model provides an accurate starting point for design and analysis and, in doing this, provides a better insight into the signal integrity performance of the filte