EXFO FTB -5240S/5240BP Optical Spectrum Analyzer for FTB 500 (NS-1434) - Manual (Page 278)

Testing DWDM Systems
270 FTB-5240S/5240BP
Using the Discover Feature
than 0.001 nm or 0.001 GHz, then their width is reduce to the lower width.
If the width of two channels is at 25 GHz and they still overlap, then the
width is not reduced and application considers it as a multi-peak signal
(like recent modulation formats for 10 Gb/s or 40 Gb/s) and sets the width
of the channel to 50 GHz and calculates the results based on this
information.
A new single acquisition starts using the modified wavelength range. The
in band acquisition option is always inactive and the analysis is performed
on each channel. The application displays the results and graph for the
detected channels and the newly discovered analysis parameters are
applied automatically to the analysis setup without displaying any
confirmation message.
One of the limitations of using the Discover feature is that the channels are
discovered based on the ITU-Grid. All detected peaks will be aligned with
an ITU-channel and the channel width and channel distance are computed
and fit in one of the ITU grids (25, 50, 100 or 200 GHz). If your channel is not
based on the ITU grid, the results may not be correct. In this case, you can
use the default channel definition or create a new channel list.