We address the generation of intensity correlations
arising from the interference between two optical
states interacting through a beam splitter. We consider
both phase insensitive and sensitive states and write the
intensity correlations as functions of the mean number
of photons and field quadratures of the input states. In
particular we consider Fock number states and squeezed
states as a paradigm of non-classical states and mixture
of coherent states, which can be experimentally accessible.
We show that, under certain conditions on the input
states, intensity correlations may vanish or turn into anticorrelations.