Optical waveguide segments based on geometrically unbound photonic crystal fiber (PCF) designs could be exploited as building blocks to realize miniaturized complex devices that implement advanced photonic operations. Here, we show how to fabricate optical waveguide segments with PCF designs by direct high-resolution 3D printing and how the combination of these segments can realize complex photonic devices. We demonstrate the unprecedented precision and flexibility of our method by fabricating the first-ever fiber polarizing beam splitter based on PCFs. The device was directly printed in one step on the end-face of a standard single-mode fiber and was 210 µm long, offering broadband operation in the optical telecommunications C-band. Our approach harnesses the potential of high-resolution 3D printing and of PCF designs paving the way for the development of novel miniaturized complex photonic systems, which will positively impact and advance optical telecommunications, sensor technology, and biomedical devices.