In previous versions, the only way to use Active Duplicate was with "image copies". However Oracle 12c introduced a new feature for Active Duplicate operations, now it is possible to do the duplication of the database with BackupSets. This way we avoid to transfer the complete file through the network. Using BackupSets allows oracle to use the special format in order to skip unused blocks, committed undo blocks etc..
This is a companion discussion topic for the original entry at https://blog.toadworld.com/oracle-active-database-duplicate-using-backupsets