  This paper addresses multi-user quantum key distribution networks, in which
any two users can mutually exchange a secret key without trusting any other
nodes. The same network also supports conventional classical communications by
assigning two different wavelength bands to quantum and classical signals. Time
and code division multiple access (CDMA) techniques, within a passive star
network, are considered. In the case of CDMA, it turns out that the optimal
performance is achieved at a unity code weight. A listen-before-send protocol
is then proposed to improve secret key generation rates in this case. Finally,
a hybrid setup with wavelength routers and passive optical networks, which can
support a large number of users, is considered and analyzed.
