  Phase-space analysis has been widely used in the past for the study of
optical resonant systems. While it is usually employed to analyze the far-field
behaviour of resonant systems we focus here on its applicability to coupling
problems. By looking at the phase-space description of both the resonant mode
and the exciting source it is possible to understand the coupling mechanisms as
well as to gain insights and approximate the coupling behaviour with reduced
computational efforts. In this work we develop the framework for this idea and
apply it to a system of an asymmetric dielectric resonator coupled to a
waveguide.
