  We calculate numerically the capacity of a lossy photon channel assuming
photon number resolving detection at the output. We consider scenarios of input
Fock and coherent states ensembles and show that the latter always exhibits
worse performance than the former. We obtain capacity of a discrete-time
Poisson channel as a limiting behavior of the Fock states ensemble capacity. We
show also that in the regime of a moderate number of photons and low losses the
Fock states ensemble with direct detection is beneficial with respect to
capacity limits achievable with quadrature detection.
