The optical fibre technology currently allows the fabrication of low loss optical waveguides providing both single mode and multimode wave guiding at a number of wavelengths and for various maximum optical power levels. The fibre optic technology is fairly advanced and provides many high-quality optical components. The weakness of fibre optic technology lays in the large dimensions of the components and in its limited suitability for low-cost mass production. Planar technology, on the other hand, has the potential to provide the low-cost large-scale production of compact optical components, which can meet the demands of the modern telecom systems and other applications.