An adapter assembly includes a single-piece or two-piece multi-fiber adapter defining a recess at which a contact assembly is disposed. The adapter assemblies can be disposed within adapter block assemblies or cassettes, which can be mounted to moveable trays. Both ports of the adapters disposed within adapter block assemblies are accessible. Only one port of each adapter disposed within the cassettes are accessible. Circuit boards can be mounted within the block assemblies or cassettes to provide communication between the contact assemblies and a data network.