BER and eye diagram

[boldooParticipant]

Hello everyone,

I’m doing 16QAM signal. I got constellation diagram. but , i can’t get any result about BER and eye diagram. it is still null.

please help me to find where i did mistake.
See attachment.

Thanks a lot

[boldooParticipant]

is there must be DSP when I want to get BER and eye-diagram?

for star-16QAM, there is no DSP in Optisystem. how can I get almost real values for BER?

[boldooParticipant]

my schema is attached. Eye diagram is seems like very big. is there any way to correct it?

Attachments:

1. star-16QAM.osd

[RavilParticipant]

Hi Boldoo, the main functions of DSP are forward error correction (FEC) encoding, constellation mapping (MAP), fiber nonlinearity compensation (NLC), up-sampling (UpS), electronic dispersion precompensation (EDC), Nyquist prefiltering. As far as I know there is no DSP in OptiSustem. This component (written in Matlab) can be found in ‘100 Gbps DP-QPSK System with DSP’ example.

[RavilParticipant]

Usually, to get BER values you should compare the PRBS from generator to the ones you obtain from receiver for each channel. Can you, please, upload the screen shot of your scheme as well?

[Damian MarekParticipant]

Ravil makes some good points, but I will also point out an error in your project. A common mistake for calculating the BER is using the BER Analyzer for a QAM signal. Since in your design you are detecting the QAM seqeuence and then generating a new one, the eye diagram will be near perfect with no noise.

Search the forum for BER Test Set examples or you could also use the error vector magnitude estimation from the constellation diagram.

Regards