To qualify passive fibers for (high power) laser beam delivery, different experimental approaches (interferometric, heterodyn, M 2, ...for beam characterization at fiber output are under test in the community. Measurement of the individual strength of different components (eigenmodes) contained in the superposition at the fiber output in dependence for example on bending radius seems to be very promising. This can be done by means of optical correlation filters based on DOEs. For a standard telecommunication fiber SMF-28, operated at 633 nm, this could be demonstrated earlier1 by us. Here we present experimental results for quantitative proof of LP modes in LMA fibers as well as in SMF-28 fibers by means of such correlation filters, and demonstrate potential and limitations of this approach.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.