  We present a detailed theoretical analysis for the distillation of one copy
of a mixed two-mode continuous-variable entangled state using beamsplitters and
coherent photon-detection techniques, including conventional on-off detectors
and photon number resolving detectors. The initial Gaussian mixed-entangled
states are generated by transmitting a two-mode squeezed state through a lossy
bosonic channel, corresponding to the primary source of errors in current
approaches to optical quantum communication. We provide explicit formulas to
calculate the entanglement in terms of logarithmic negativity before and after
distillation, including losses in the channel and the photon detection, and
show that one-copy distillation is still possible even for losses near the
typical fiber channel attenuation length. A lower bound for the transmission
coefficient of the photon-subtraction beamsplitter is derived, representing the
minimal value that still allows to enhance the entanglement.
