wdm-ofdm pon

[ELAARAIND M]

sir we are confusing about FFT size ,position array,number of subcarrier ,cyclic prefix in ofdm modulator block.BY using no.of subcarrier 512,position array 256,FFT size 1024,cyclic prefix 64 we have got the Q-factor 10^49 and min BER is 0.is it correct this is our ques?.And also
1. IN WDM/OFDM PON,we retrieve the downstream at ONU.BER is 0 q factor is 10^49 . But upstream signal not send after the AWG mux demux block but we have same output at OLT in BER give us some idea sir.if any one know give us some idea.
2.AND also if we are using different wavelength in upstream and downstream ,we have got the result in ONT not get the result at OLT

[ELAARAIND M]

any one help us and give some idea.we are final year ,we are submit our final report within this month .give us support

[Damian Marek]

I can only give a short response because I am away at a conference. However, the primary issue is using the BER Visualizer in Gaussian mode when an OFDM technique is implemented. There are a couple posts here on the forum where I explain why the BER Test Set is better used. Please check them out.

Regards

[kostas halkidian]

In the OFDM block position array arranges the position of the central frequency of the OFDM spectra.For example: put “0” and after that put the value “(Nifft-Nsub)/2” (i.e (128-64)/2=32) and compare. In first case you almost see nothing because your OFDM spectra has been removed to “negative” frequencies. In second case you see the half of the OFDM spectrum and the central frequency of it, is found in the frequency 0 of the diagram. If you put position array 64 with the same, as before, parameters, you will the whole spectra.
Mind the BW of the spectra for each (I or Q) stream, must be the BitRate/2.

cyclic prefix will confuse you. Without cyclic prefix, using symbol extension, will keep orthogoanlity without concern!

About BER, i use BER test set. You will find it: Default/ Test set/ Binary
About its action in your block diagram, seek help topic of the block.

Good luck!

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