We report the experimental demonstration of all-optical wavelength multicasting of OC-768 (40 Gbps) channel using a single-pass, pump modulated parametric amplifier. The performances of 1-to-20 and 1-to-40 multicasting with excellent signal fidelity were observed. The impairment mechanisms were identified from cascaded filtering, linear and nonlinear crosstalk. It is shown that the parametric amplifier offers a wide range of operation characterized by minimal multicast penalty.We show that all multicast channels have an error free performance with Q factors well above the forward error correction (FEC) limit within the designed operating range.