This thesis presents recent approaches in the development of a Si-based waveguides system for submicrometer devices. A compact and efficient grating coupler for tilt-incident with respect to the vertical axis coupling between optical fibers and silicon photonic wires is proposed. One of the drawbacks of the high index contrast is the large mismatch in mode size and shape between fibers and silicon photonic wires. Hence, a perfectly vertical fiber coupling is achieved by using an asymmetric grating structure to suppress the second order Bragg reflection from the grating. We use R-Soft to simulate our approaches and micro-genetic algorithm to find the best solutions.