  We propose a novel scheme for continuous variable quantum key
distribution(CV-QKD) using the subcarrier multiplexing technique which was
employed in microwave photonics. This scheme allows to distribute N channels
independent Gaussian modulated CV-QKD in parallel with one laser source and
several phase modulators. We analyze the influence of nonlinear signal mixing
and the security in the asymptotic limit. Results indicate that by using this
multiplexing technique, each channel will be introduced a non-Gaussian extra
source noise, resulting slightly short of the maximum transmission distance,
while the total secret key rate can be considerably increased. This scheme
could also be used for key distribution for multi-users and combined with the
WDM devices it has the potential to construct a CV-QKD network.
