EXFO FTB-8500 Series for FTB-500 - Manual (Page 150)

Port Tabs
136 FTB-8500 Series and FTB-8120NGE/8130NGE
Optical TX
Optical TX
Press TEST, Port, and Optical TX.
Signal Analysis

Output Presence: Indicates the presence of a signal at the output port
(green) or not (grey). The output presence LED is grey when there is
no SFP/XFP.

Wavelength (nm): Indicates the detected SFP/XFP wavelength.
Possible values are 850, 1310, 1550 nm, or unknown if the SFP/XFP is
missing or not recognized.
Alarm Generation
Note: Alarm generation is not available with RFC 2544 test.

Type
LOS (Loss Of Signal): Turns off the output port laser signal.

On/Off button: Allows enabling the alarm generation. This setting is
disabled (Off) by default.