EXFO IQS-8500 Series for IQS-600 - Manual (Page 31)

Physical Interfaces and LEDs
Ethernet and Fibre Channel Application 17
IQS-8510G Model

LEDs
LASER LED: The red LASER LED is on when the IQS-8500 Series and
IQS-8120NGE/8130NGE is emitting an optical laser signal.
LINK/ACT LED: The LINK/ACT LED is on when the link is up, off when
the link is down, and flashing when frames are transmitted and/or
received.
C
AUTION
To prevent exceeding the maximum input power level, please use
an attenuator when a loopback configuration is used.