This thesis presents a theoretical and numerical investigation of silicon-on-insulator trench based passive optical components, bend and splitter, respectively. Compact 90 degree and 105 degree bend and splitter are designed with high index-contrast rib waveguide at wavelength 1550nm and serve as building blocks of splitting network in micro-cantilever biosensing application. The main characteristic of trench based bend and splitter structures is their miniature size and their low radiation loss due to the strong light confinement in high index-contrast systems. Thus large scale, high density optical integrated splitting network becomes possible with the associated advantages of compactness. With FDTD simulation, we show that single-mode trench based bends and splitters exhibit around 16000nm X 16000nm overall size with low loss for different bending angle. Total efficiency is about 92.9% (90 degree bend), 89.3% (105 degree bend), 92% (90 degree splitter) and 84% (90 degree splitter) respectively.