  AgCrSe$_2$ is an example of a super-ionic conductor that has recently
attracted attention for its low thermal conductivity. Here we investigate the
optical properties of AgCrSe$_2$ in the ordered phase between 14 K and 374 K
using reflectivity experiments. The far infrared optical response is dominated
by three phonon modes, while six interband transitions are observed in the
visible range. From our analysis we find that the phonon parameters display an
interesting temperature dependence around the N\'eel temperature, pointing to a
small magneto-elastic coupling. In addition, the lifetimes of the modes
indicate that three-phonon processes dominate and the optical phonons decay
into low energy acoustic modes involved in the super-ionic transition. Finally,
we detect a small free charge carrier response through the analysis of
Fabry-Perot interference fringes in our reflectivity data.
