EXFO FTB-5230S Optical Spectrum Analyzer for FTB 200 v2 - Manual (Page 85)

Setting Up the Instrument in WDM Mode
OSA/OCA 79
Setting Up WDM Analysis Parameters
2. Select the Default Thresholds tab.
3. Enter values in the boxes as explained below:

Wavelength/Frequency (nm/GHz): the channel’s central
wavelength/frequency.

Signal power (dBm): the signal power for the default channel
(excludes noise).

Noise (dBm): the level of the noise for the selected channel.

OSNR (dB): the optical signal to noise ratio, given by Signal power
(according to the current calculation method, in dBm) minus
Noise (according to the current calculation method, in dBm).
4. Press OK to save the changes and close the window, or press Cancel to
exit without saving.
Press Restore Defaults to remove all the changes and apply the default
values.