- This topic has 12 replies, 3 voices, and was last updated 8 years, 8 months ago by alistu.
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February 29, 2016 at 11:48 pm #30569mukalla pavanParticipant
hi
i want to replace 16-qam instead 4-qam in coherent optical qam wdm optical ofdm..but i am getting bit error rate of 0.483please suggest me the changes needed
i am attaching the file
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March 1, 2016 at 1:12 am #30596alistuParticipant
Hi Mukalla,
I have noticed a few parameters in your system that need to be changed. First of all, the number of cyclic prefix points should be the same both for OFDM modulators and demodulators. Second, The value of symbol rate should be set according to the coding scheme in layout parameters and in OFDM blocks. Please see if these help.
Regards
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March 1, 2016 at 9:22 am #30687mukalla pavanParticipant
thank you alistu
with the changes you suggested system working somewhat better. But still ber of 0.35 in one channel and 0.26 in another
what to do to reduce ber ?
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March 1, 2016 at 12:04 pm #30741alistuParticipant
You’re welcome. Can you please upload the new .osd file in which you have made the aforementioned changes? I also believe the bandwidth of some of the filters is a bit more than what is required, but even so the system is supposed to work properly after the above changes are applied to it.
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March 1, 2016 at 9:08 pm #30785mukalla pavanParticipant
i am uploading new osd file
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March 2, 2016 at 12:01 am #30803alistuParticipant
Hi Mukalla,
having done the changes that I suggested, you have very clear constellation diagrams, which shows transmission is done correctly. However, in order to overcome the symbol rotation, you can change the receiver laser phase so that constellation points fall into the correct quadrants.
Regards
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March 2, 2016 at 10:02 am #30952mukalla pavanParticipant
ok alistu
i will try by changing laser phase at receiver
thank you
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March 2, 2016 at 1:35 pm #31007alistuParticipant
Hi Mukalla,
Please see if the change in the laser makes the BER zero when the constellation points are all in their corresponding quadrant for your 16-QAM and 64-QAM implementations. Otherwise, the problem you are facing may be due to the fact that OS12 OFDM components have been used in your design.
Regards
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March 2, 2016 at 1:43 pm #30843Ranjeet KumarParticipant
Here, I am uploading a new osd file bidirectional wdm ofdm pon. May this file help you to solve your problems.
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March 2, 2016 at 5:15 pm #31031alistuParticipant
Hi Ranjeet, Thank you very much. I find your implementation quite helpful.
Mukalla, The file attached by Ranjeet is quite helpful for your purpose. The thing is, it is a bidirectional system due to being implemented as a passive optical network. But you can easily make changes to make it suitable for your own purpose if bidirectionality is not desired.
Regards
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March 4, 2016 at 1:38 am #31379mukalla pavanParticipant
Thank you alistu and ranjeet kumar
changes in laser not giving BER 0
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March 4, 2016 at 1:42 am #31383mukalla pavanParticipant
i am not understanding ranjeet kumar file
could you please explain me clearly how it helps to solve my problemthank you
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March 4, 2016 at 1:58 am #31389alistuParticipant
Ranjeet’s file is a simulation of a bidirectional OFDM system and is designed for the purpose of being used in passive optical networks, while your simulation should be unidirectional. So I suggest you eliminate parts of the system corresponding to upstream data to have the unidirectional system.
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