  We consider a multiphoton Bell-type inequality to study nonlocality in
four-mode continuous variable systems, which goes beyond two-photon states and
can be applied to mixed as well as states with fluctuating photon number. We
apply the inequality to a wide variety of states such as pure and mixed
Gaussian states (including squeezed thermal states) and non-Gaussian states. We
consider beam splitters as a model for leakage and show that the inequality is
able to detect nonclassicality of noisy Gaussian states as well. Finally, we
investigate nonlocality in pair-coherent states and entangled coherent states,
which are prominent examples of nonclassical, non-Gaussian states.
