Locking optical and/or electrical connectors and cable assemblies

A blocking member is sized and shaped to be installed beneath a trigger or triggers of a duplex connector. The blocking member prevents depression of the trigger(s) of the duplex connector and hence prevents depression of latches to release the plugs of the duplex connector from mated receptacles. The blocking member does not block actuation of the latches of the duplex connector. Through the use of a tool, the trigger(s) may be bypassed and the latches operated directly by the tool to release the plugs of the duplex connector when mated to receptacles.