A technique for automated online inspection of manufacture of a fibre reinforced polymer composite part during automated ribbon placement (e.g. ATL or AFP) uses interferometric inspection (e.g. OCT) to detect deviations from a planned lay-up for the part, to identify defects. On line, real-time inspection (i.e. on-the-fly) is demonstrated, and edge type defects and whole surface defects are identifiable. A sensor is demonstrated that does not extend a working envelope of the robotic head used for rib bon placement.