EXFO FTB -5240S/5240BP Optical Spectrum Analyzer - Manual (Page 227)

Setting Up the Instrument in EDFA Mode
OSA 221
Setting Up EDFA Analysis Parameters

Channel width (GHz or nm): indicates the limit inside which the
power values will be considered in the channel.
For default channels, the channel width that sets the limits of the
channel, should be the same as the channel distance or smaller
(channel distance is defined while creating a channel list). If the
channel width is not compatible with the channel spacing, either a
single peak may be found for two distinct channels and two
analysis would be performed and displayed for that peak, or, it is
possible that two peaks may be found within the same channel
and be considered as one multi-peak signal. With this result, you
can use markers to find the spacing between adjacent channels or
to find the channel width.

Snap to ITU Grid: When selected, each detected peak will be
defined by the nearest ITU channel. The ITU grid is based on the
selected channel width.
4. Under Global analysis parameters, define the following parameters
as needed: