Invited paper: Characterization of few mode fibers and devices

This paper reviews characterization techniques for few mode fibers and components. The focus is on interferometric techniques including spatial and spectral resolved imaging (S-2). Simple interferometric measurements are shown to be able to give quite comprehensive information including measurement of relative group delay. A new improved algorithm for analyzing S-2 data for the case of only two modes is presented. The effect of polarization and rotation of asymmetric modes is treated as well.