The booming telecom market pushes the development towards highly integrated optical devices. For a breakthrough in the increase of packaging densities, a bypass of the limited horizontal dimension of a waveguide chip is necessary. This leads to an introduction of a vertical integration scheme which needs an adapted fabrication method to meet the requirements of integrated optical applications. To this end, a newly developed technology for the stacking of mono-mode waveguides using inorganic-organic hybrid polymers (ORMOCERs) is presented. Besides important advantages concerning an efficient fabrication by UV lithography methods, the stacking process faces several fundamental problems, e.g., broadening of the structures by scattering during UV patterning or the occurrence of index inhomogenities constituted by diffusion effects. Both problems could be solved in the framework of conventional processing techniques, which will be presented. The key points of the new technology, a UV absorber method and a combined UV and thermal curing, are investigated in detail. On the basis of this development the design, fabrication as well as the test of a novel optical fan-out element is discussed. The device consists of four stacked layers of single-mode waveguides, which enables one to accomplish signals from different sources to an output adapted to a single detector. Experimental results as well as the potential for future applications are presented.