  Explicit expressions are determined for the photon correlation function of
``blinking'' quantum systems, i.e. systems with different types of fluorescent
periods. These expressions can be used for a fit to experimental data and for
obtaining system parameters therefrom. For two dipole-dipole interacting $V$
systems the dependence on the dipole coupling constant is explicitly given and
shown to be particularly pronounced if the strong driving is reduced. We
propose to use this for an experimental verification of the dipole-dipole
interaction.
