  A multimode optical fiber with a truncated transverse cross section acts as a
powerful versatile support to investigate the wave features of complex ray
dynamics. In this paper, we concentrate on the case of a geometry inducing a
mixed dynamics. We highlight the properties of regular modes associated to
stable periodic orbits such as an enhanced intensity localization and report
unexpected attributes such as the statistics of the Inverse Participation Ratio
that present features analogous to those of Anderson localized modes. Our study
is supported by both numerical and experimental results.
