This CoriantTypesEnableSwitch (default disabled) turns loopback testing on or off for an OTU2e (enhanced OTU2, roughly 11.1 Gb/s) trunk carrying an oversized client signal such as 10GbE LAN. An administrator enables it during maintenance or fault isolation to loop the signal back at this facility and determine whether a suspected problem lies in the local equipment or further out in the network. For example, a technician suspecting a faulty transceiver would enable loopback on OTU2e, then check whether locally generated test traffic returns correctly before deciding whether the fault is local or downstream.