EXFO FTB-5230S Optical Spectrum Analyzer for FTB 200 v2 - Manual (Page 119)

Setting Up the Instrument in Drift Mode
OSA/OCA 113
Setting Up Drift Analysis Parameters
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.

Noise for OSNR: indicates which calculation method to use for
OSNR value (InBand and InBand narrow filter are available for
viewing or reanalysis purposes only when opening files from other
OSA models).
Fixed range IEC based (IEC): The IEC method uses the
interpolation of noise measured on both sides of the signal to
estimate the noise level. The position at which the noise is
estimated from the center wavelength is given by the OSNR
distance.
InBand (InB): The InBand method uses a series of scans having
different polarization states to calculate the noise level under the
peak (InBand).
InBand narrow filter (InB nf): The InBand narrow filter method
uses additional processing to provide an accurate OSNR value for
the narrow carved noise. This is because with narrow filters, the
noise level under the peak is not uniform and the OSNR value
depends on the processing width selected.