Electrical and Computer Engineering Department-College of Engineering-Sultan Qaboos University Design of DWDM Network for Omantel Main Nodes & Analysis of Scalability Issues for Higher Bit Rates Hamad Ali AL Mahrooqi Abstract In this thesis we will examine the design of Omantel DWDM upgrade project and simulate some of extreme scenarios. We shall utilize field data and vendor specifications to simulate the projects created by the OptSim software to bring the simulation process near to the reality. The upgrade project brings with it its new challenges as well as the benefits. Those challenges were not faced as such by telecom operators. Hence there will be a consideration devoted to the dispersion compensation scheme utilized with this project and its risks in changing system specification and parameters. Some of theoretical DWDM challenges and fiber nonlinearities are linked to Omantel upgrade project. The main concerns will be the Chromatic Dispersion (CD), Polarization Mode Dispersion (PMD) and the nonlinear effects. Then we confirm that the design has enough margins to deliver the capacity and the resilience that it is designed for.