Optical transceiver and cage system to prevent insertion of new transceiver models into legacy cages

To prevent newly developed transceiver modules from being plugged into legacy cages, which may not have the correct electrical connector therein, the new transceiver modules are built with one or more tabs extending outwardly therefrom for abutting an edge of the opening of the cage, thereby preventing the transceiver module from being fully inserted into the cage. New cages, which include the correct electrical connector, are built with slots extending from the opening of the cage to enable the tabs to pass freely, thereby enabling the transceiver module to be fully engaged in the new cage.