BER Analyzer Response at different bit rates

[Sanjeev kumar]

Hello everyone,
I have a very urgent query regarding the response of the BER analyzer as i have seen that whenever we set the bit rate to some optimum level say at 30Gbps the response shown by BER analyzer is very good with Q Factor of 15 and BER of 10^-20 but when i set the bit rate to 28.8 the response goes down with Q Factor only 5 and BER is only 10^-6 what does it means.
Do i have designed a wrong Transmitter?
or there is some parameters that decides the output response?
is there any phase relationship rquired to get the output response?
why system is showing too large output response fluctuation at slight bit rate change … as changing bit rate from 30Gbps to 28.8Gbps is not large but reponse changed too much …where is the discrepency? why it is happening?

[Sanjeev kumar]

Is there anyone facing the same problem?

[Dr. Dhiman Kakati]

Hello Sanjeev Kumar,
This problem occurs may a times when your system bit rate and symbol rate (that you have taken at the layout properties) do not match with that of your transmitter. try to set prbs generator bit rate in script form and write there Bit rate. I think this should solve your problems. Thanking you.

Regards,
Dhiman

[Sanjeev kumar]

Thanks for your kind feedback sir,
I have already done this but even then the problem exists. i have already learnt this thing. there is some other problem as PRBS bit rate script does not change my results.

[Dr. Dhiman Kakati]

Hi Sanjeev,
If you have tried this out and still your problem exists, to make any further comment on or solution I need to look into your design, If it is possible please attach the design .osd file here.

Regards,
Dhiman

[Sanjeev kumar]

Attachment uploaded.

[Dr. Dhiman Kakati]

Hi Sanjeev,
I think you have missed the attachment, Please reupload again.

Regards,
Dhiman

[Sanjeev kumar]

Attachment uploaded now

[Dr. Dhiman Kakati]

Hi Sanjeev Kumar,
I think you have done some major mistakes because you are using continuous phase frequency shift keying (CPFSK) sequence generator as seen from the attached image and applying it to modulate the optical signal using MZM modulator. but at the receiver side you have not done the decoding of the CPFSK sequence. I am not aware of this system. I have to try from my own to have a confirm answer.

Regards,
Dhiman

[Sanjeev kumar]

Sir there is no decoding available to decode CPFSK data. if u know something about it please guide me.

[Dr. Dhiman Kakati]

Hello Sanjeev Kumar,
Yes I agree with you that there is no CPFSK decoder in Optisystem Components library, I did post this issue regarding MSK decoder as MSK is a special kind of CPFSK, in another topic then I was Suggested please have a look to the following links…

MSK Modulator

MSK transmitter constellation

how to separate even and odd bit.

MSK sequence decoder

Regards,
Dhiman

[him ind]

HI,
I would like to simulated and learn about the 40 gbps bidirectional transmission (upstream 1550nm downstream 1310nm) system about which video and necessary document is available on optiwave site. I shall be thankful if anyone can share this .osd file with me at himnariyal30@gmail.com.
Thanking you in anticipation.

[Naazira Badar]

Hi Sanjeev Kumar
Firstly I surprised that the Q.F and BER performance has deteriorated on reducing the bit rate.

Secondly, I think Dhiman has rightly pointed out about the absence of the decoder circuitry at the receiver end.

All the best.

Regards
Naazira

[Ranjeet Kumar]

Hi Sanjeev kumar,
I agree with the points of Dhiman kakati that the “problem occurs many a times when system bit rate and symbol rate do not match with that of your transmitter, so we have to set prbs generator bit rate in script form and write there Bit rate”.
I also think that when we design the networks as per our requirements , then we should know the different standard values of corresponding parameters as per ITU- standards.
We should not use random values of different parameters and always follow the standard one.
We could take help from the sample of different designs of optisystem.

[Dr. Dhiman Kakati]

I totally agree agree with sanjeev kumar that the system we design must meet the specification or follow ITU standards such as frequency allocation, bandwidth etc.

Regards,
Dhiman

[SAHIL SINGH]

Hi Sanjeev kumar,

I agree with the view of Dhiman kakati as well as Ranjeet Kumar that problem many a times is because of the fact that system bit rate and symbol rate do not match with that of your transmitter… Also try using the standard values of different parameters…

Regards

Sahil Singh

[Dr. Dhiman Kakati]

Hello Sanjeev Kumar,
Did you checked how much power is arriving at the receiver, The received power also has some deciding criteria, So please let us know how much power you are getting at the input of the system. Thanking you.

Regards,
Dhiman

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