A technique is proposed for performing add/drop operations in an OADM assembly serving an optical network and comprising an add unit and a drop unit. With respect to at least one optical channel assigned to an optical wavelength λ, the OADM assembly is capable of dropping the channel from the network via the drop unit as a first signal, and adding the channel to the network via the add unit as a second signal. According to the technique, the OADM assembly additionally comprises an authentication and control unit ACU for authenticating the at least one optical channel and controlling the OADM assembly. The ACU is authenticates the optical channel by comparing one or more components of the first signal with one or more components of the second signal serving as a reference, and based on the authentication result, makes decisions whether to allow or block the dropping and/or adding of the optical channel.