EXFO FTB-800 Series for FTB-1 - Manual (Page 480)

Test Control
470 FTB-700G/800 Series
Lpbk Tool Button (Loopback Tool)
Lpbk Tool Button (Loopback Tool)
The Loopback Tool provides the capability of looping back the Ethernet
frames/packets that are received on the loopback tool port.
Pressing the Lpbk Tool button opens the Loopback Tool pop-up and
powers up the port unused by the main test application (it does not start
looping back the frames yet). The Loopback Tool starts looping back the
Ethernet frames/packets that are received when pressing on the Loopback
button from the Loopback Tool tab.
Note: The Lpbk Tool button is available when the main test application is any
Ethernet test application at the exception of Through mode.
Note: The Loopback Tool is independent from the main test Start/Stop, Reset
and Test Timer.
Note: Enabling/disabling the Laser control affects both the main test application
and the Loopback Tool when applicable (if both test and tool are using an
optical port).