CONVERT NOISE BIN

[Joseph JiangParticipant]

HI EVERYBODY,I have found that if i select convert noise bin(the noise that overlaps the signal will be converted to sampled signal,the sampled signal power will be added ),the osnr and snr measured by wdm analyzer will be higher than not to be selected.I think that is not the exactly right osnr and snr.how about electrical carrier analyzer?is it measured the right SNR if i selected convert noise bin,since i am interested in the snr in electrical domain.thank you !

[Alessandro FestaParticipant]

Hi Joseph, I also noted in the past that sometimes Convert Noise Bins gives inaccurate OSNR results. Which version are you using?

[Joseph JiangParticipant]

optisystem 13.0 @damian could you give us a help？thank you!

[Damian MarekParticipant]

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.

Attachments:

1. SNRwithNoiseBins.osd

[Joseph JiangParticipant]

dear damian,i am still confused about it.when the noise is converted to sampled signal,the signal will have a higher power at the central frequency.is it the right snr when the noise is converted to sampled signal(since the signal will be higher)?how the visualizer distinguish the signal and noise?thank you!

Attachments:

1. SNRwithNoiseBins1.osd

[Joseph JiangParticipant]

dear Damian,are you busy doing your work.I am waiting for your reply!thank you!

[Damian MarekParticipant]

Hi Joseph,

I’ll be back in my office next week. The signal power will increase because OptiSystem is adding the noise bins to it. In a lab setting generally you don’t have as much knowledge about how to distinguish the noise power from the signal power, so generally the peak power is compared to a power far from the peak frequency. Possibly in between channels or if the channels are too close then outside the channel frequencies range. If you want to get an SNR the same as on you might measure in a lab then convert the noise bins and choose an interpolation point in between channels or far from the channel frequencies.

Regards

[RavilParticipant]

Damian, how did you choose your interpolation offset? is equal to grid spacing?

[Joseph JiangParticipant]

Dear RAVIL,can you help me to solve my question?thank you!

[Damian MarekParticipant]

Hi Ravil,

I chose a interpolation offset of half the channel spacing. However, depending on how close your signals are in the frequency domain then it might make more sense to interpolate outside the channel frequencies.

Check the Technical Background for the WDM Analyzer component and look at the ways it calculates the SNR/OSNR.