PAM Example Optisystem

[Shahid]

How I can replace the BERT Tester with Eye Diagram Analyzer for the attached PAM example from Optisystem13 samples.

I have attached the example file. I think example implements PAM4.

Thanks

[alistu]

Hi Shahid,

I have attached the modified file in which BER Test Set has been replaced by BER Analyzer using two more NRZ pulse generators and a fork. I have replaced BER Test Set with PRBS generator to generate the data bit sequence, but you could have kept both of them just by keeping BER test set.

Regards

[Shahid]

Im unable to open your file.
Im using version 13.0.2.163. If possible could you attach the screen shot?
Thanks

[alistu]

Here I have attached a screen shot of the modified implementation. You are not able to open the file because I am using OptiSystem version 13.0.3. After calculation, he BER analyzer works and shows very good BER and Q-factor, which corresponds to the zero error you were getting using BER test set before.

Regards

[Shahid]

Thanks Alistu for the screenshot.
The system implements PAM4?

[alistu]

You’re welcome Shahid. Yes, the number of bits per symbol is 2 in the modulator and demodulator and therefore, modulation scheme is 4-PAM (which has four signal power levels).

[Shahid]

Have implemented the system from your screenshots but the Q-Factor and BER values are 0 and 1 for Fiber distance (BtB to 10 km).
After this there is value of Q=1e50 and BER=0 from 20km to 60km. and then again Q=0 and BER=1 from 70Km onwards.
The vlaues seem very strange and if you look at the eye pattern it doesn’t look like PAM4.

Have attached my project file.

[alistu]

You’re right. I couldn’t figure out what is wrong with the system that shows better error for longer distances and shows only zero error or BER=1 yet, but eye pattern is connected to the signal after being decoded by PAM and becoming binary signal. If you want to see it with three eyes, you can connect it to low-pass filter output.

[Shahid]

I have checked the other example (PAM fiber link w Threshold Detector) for PAM in Optisystem samples. It also shows the same result of Q=0 and BER=1, is there anything wrong with the system in example? How to get help from optiwave support?

[alistu]

I have also come across the same problem for a few times, even though I cannot remember exactly the cases. In order to get help from Optiwave technical support, you only need to send a mail to support@optiwave.com and explain your problem. You have to wait until the end of the weekend for the answer, though.

[Damian Marek]

Shahid,

Hopefully I can clear up these issues for you. I believe the main issue is the use of the BER Analyzer placed after the decision component. This is why the eye diagram is looking so strange because it is “perfect”. Even though the decision components might have made some errors.

For advanced modulation formats, the eye diagram makes a lot less sense to use, so in general we use the BER Test Set which simply compares the input bit sequence to the output and counts the errors.

I suggest using the BER Test Set in the Test Sets library!

Regards

[Leopoldo Coque]

(Awaiting moderation)

[Leopoldo Coque]

(Awaiting moderation)

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