  We address the use of optical parametric oscillator (OPO) to counteract
phase-noise in quantum optical communication channels, and demonstrate
reduction of phase diffusion for coherent signals travelling through a suitably
tuned OPO. In particular, we theoretically and experimentally show that there
is a threshold value on the phase-noise, above which OPO can be exploited to
squeeze phase noise. The threshold depends on the energy of the input coherent
state, and on the relevant parameters of the OPO, i.e. gain and input/output
and crystal loss rates.
