  Topological solitons are relevant in several areas of physics [1]. Recently,
these configurations have been investigated in contexts as diverse as
hydrodynamics [2], Bose-Einstein condensates [3], ferromagnetism [4], knotted
light [5] and non-abelian gauge theories [6]. In this paper we address the
issue of wave propagation about a static Hopf soliton in the context of the
Nicole model. Working within the geometrical optics limit we show that several
nontrivial lensing effects emerge due to nonlinear interactions as long as the
theory remains hyperbolic. We conclude that similar effects are very likely to
occur in effective field theories characterized by a topological invariant such
as the Skyrme model of pions.
