Polymer optical fibres (POF) are used for data transmission. Industrial automation and vehicle applications use them to a larger scale. During assembly, installation and operation of polymer optical fibres accompanying tests are necessary for quality assurance. The series of standards VDI/VDE 5570 helps to improve quality of tests and measurements on polymer optical fibres by enabling better reproducibility and comparability of results. This standard defines basic terms for testing optical light guides using polymer optical fibres consisting at least of an optical core and an optical cladding with step index profile. Thus, it a basis for better and easier communication of manufacturers, distributors and users - not only on testing, but also on using polymer optical fibres.