EXFO IQS-1600 High-Speed Power Meter for IQS-500/600 - Manual (Page 29)

Setting Up Your High Speed Power Meter
High Speed Power Meter 21
Setting Channel Display(IQS-1620, IQS-1640)
Selecting a Channel (IQS-1620, IQS-1640)
The IQS-1620 and IQS-1640 have two and four independent optical
channels respectively.
To select an optical channel:
From the Instrument function tab, go to Channel and use the arrow
buttons next to the channel number to change it.
OR
Click the appropriate data display zone.
A colored frame will indicate your selection.