  We investigate the optical activity of tilted nodal loop semimetals. We
calculate the full conductivity matrix for a band structure containing a nodal
loop with possible tilt in the $x-y$ plane, which allows us to study the Kerr
rotation and ellipticity both for a thin film and a bulk material. We find
signatures in the Kerr signal that give direct information about the tilt
velocity and direction, the radius of the nodal loop and the internal chemical
potential of the system. These findings should serve as guide to understanding
optical measurements of nodal loop semimetals and as an additional tool to
characterize them.
