Hi Joseph,
I suggest converting noise bins to get a more experimental calculation for the OSNR. By that I mean when calculating SNR/OSNR with noise bins the analyzer will find the maximum signal power and then choose the noise power at that same frequency to calculate the SNR/OSNR.
When noise bins are converted you can specify where the noise power should be interpolated from, (generally in between channels or far away from frequency’s that carry signals). In the attached example file, I demonstrate the different calculations. The noise bins acquire the bessel shape of the WDM filter and thus have a higher power at the central signal frequency. For calculating the SNR/OSNR with converted noise bins I chose 50 GHz as the interpolation offset.
Let me know if this clears it up.