EXFO FTB -5240S/5240BP Optical Spectrum Analyzer User Manual
Page 63
Setting Up the Instrument in WDM Mode
OSA
57
Setting Up WDM 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.
Signal power calculation: indicates which calculation method to
apply for signal power value.
Integrated signal power: The integrated signal power represents
the sum of the power values included between the channel limits
of this channel, minus the estimated noise contribution between
the same boundaries. In some cases, for instance CATV signals,
signals with high-frequency modulation, or signals with an
inherent line width similar or larger than the OSA's resolution
bandwidth, this calculation becomes a better estimation of the
true signal power.
Peak signal power: The peak signal power represents the
maximum power value inside the channel. Note that it differs a
little from the peak measurement on the spectrum due to the fact
that the estimated noise is subtracted to get the peak signal power.
Total channel power: The total channel power represents the sum
of the integrated signal power and of the noise within the channel.
The OSNR calculation is not performed when the signal power
calculation type is the total channel power.