**4. POF demultiplexer employing thin-film interference filters**

This chapter focuses on the experimental realization of a thin-film interference filter-based SI-POF demultiplexer using a modular and precisely adjustable setup. In a step-by-step approach, the intermediate solutions with two and three channels were first established. In addition, two different configurations of the target demultiplexer setup with four channels were realized. The principle of operation and the approach for experimental realization are explained for the simplest case of a two-channel demultiplexer. The same basic principles also apply to the demultiplexers with higher channel count.
