Photonic crystal fibers contain an array of holes extending along the fiber axis and are exceptionally versatile. They can guide optical signals very efficiently, like conventional light guiding fibers applied in information technology. Infiltration with a LC can turn micro-structured fibers into controllable, integrated color-, intensity- or polarization filters. Metal nanostructures of sub-wavelength size can even yield effective material parameters that are not found in nature. Tunable metamaterials are obtained if plasmonic structures of this kind are embedded in a LC. Their transmission spectra can be controlled by thermal addressing, by applying voltages or by non-linear optical effects, such as the “colossal optical nonlinearity”, an extremely large optical Kerr effect.