BER vs Received Power Curve

[Shahbaz Qureshi]

Hi, I have been trying to obtain a BER curve vs received power like a waterfall but it gave me a straight line. I am attaching a file here. I would appreciate any help.

[Alessandro Festa]

Hi Shahbaz, can you attach the picture of the curve you obtain? I do not have access to Optisystem right now.

[alistu]

Hi Shahbaz, I ran your simulation and found nothing wrong with its performance (based on the bit error rate). Can you tell me how it is possible to plot BER vs Received power? So that I can get the figure and see if I am able to help you in any way. By the way, is it possible that by changing scale on the x axis you would get the desired figure?

[Shahbaz Qureshi]

I followed this tutorial of making a BER curve but im getting a straight line eventhough i changed parameters. I need a curve like water fall. Im giving the link https://optiwave.com/resources/applications-resources/optical-system-lesson-4-parameter-sweeps-ber-x-input-power/

[alistu]

Thank you for your explanation Shahbaz. I will try to run the simulation and get the curve to see if I can help you. In the meanwhile, could you tell me if you are simulating a system introduced in a paper? If so, I think it would be better if you introduce the paper so that we can check if you have implemented your system according to the paper. Thank you.

[Ashu verma]

Hello Shshbaaz ,can you attach a screenshot of the plot you got?Because it is possible to vary the one parameter say power and then plot BER vs Received power.I think you have missed something.Rx power id negtive value and you can plot it using -LOG[BER]
Go to report>2D graphs and then dragg -LOG[BER with Rx power.

[Shahbaz Qureshi]

Hi Sam Sung, The system plots a straight line and there’s no variation. Do you mean that we can select or vary the values in one axis by ourselves or by iterations and let the system plot the graph?

[Ashu verma]

Hi Shshbaz

for plotting the graphs you need to change the one of the values either power,distance.However received power and BEr change for each iteration value..So you can select any two values and plot the graph in your case it is Rx power and LOG[BER}.I think you are plotting the input power Vs LOG[BER} values.Otherwise the graph should be like waerfall.A screen shot of this plot attached by Essakamuthu in other forum topic.https://optiwave.com/forums/topic/back-to-back-ber-measurement/

[alistu]

I have some more doubts about the simulation, Shahbaz. I think it is necessary for me to know the number of iterations and also the start value and the amount of iteration steps for the laser power. Also, when you wanted to plot BER vs received power, where did you choose the received power on the project browser? Thanks.

[Ashu verma]

Hello Alisthu
I think in project browser you can find the value of received power from BER analyzer and the first total power in dB is referred to total received power.So by knowing the Rx power drag and drop from project layout to 2-D graphs with -LOG[BER} plot the graph i guss.

[Shahbaz Qureshi]

I understand, Alistu. No I am not following any research paper in this regard. I just simply wanted to plot the BER curve. Actually the BER curve has been shown in many research papers but I am not able to exactly obtain it in the optisystem. I exactly followed the steps of the tutorial in the above mentioned link but I am getting a straight line. I plotted the curve Received power vs min log of BER. If you will try the same steps given in that tutorial, I hope that will make it clearer to you. Thanks

[alistu]

Hi Shahbaz, In the tutorial that you had addressed, the power launched by the input laser was plotted vs min log of BRE, whereas you have mentioned that you plotted the received power. I would like to know where you found the received power parameter in the in the project browser in the report section, where you choose the axes. Thank you.

[alistu]

Right now when I simulate it and then plot the BER vs the transmitted power, I get the strange figure that I have attached from your system. And when I choose “optical power” for the x-axis from the BER Analyzer “parameters”, it doesn’t change with the iteration. So please tell me where to choose the x-axis.

[Ashu verma]

Transmitter power VS BER is the different plot,which represents the variation of BER with the input power.Usually for lower values of input power BER decrease with the increase of input power unless non linear effects comes into play.But the question is of plotting Rx power with BER which will come like waterfall as written above.Aluisthu i think your system plot defines the effects of non linearities due to the non linear variation of in the value of ber with input power.

[alistu]

BER vs Transmitted power is definitely different from BER vs the recieved power and I have vividly explained why i was not able to get that plot. I don’t know if the variations are due to nonlinear effects. Nonlinear effects happen in high power and not in the low power and the system performance gradually degrades due to these effects.

[alistu]

Here I have attached an example of a system whose performance degrades as the launched power increases. As it can be seen, the degradation starts at a certain point and the process of degradation is somehow gradual. But in the above plot, non of these happen and the changes seem to be on no basis.

[Shahbaz Qureshi]

That’s exactly what I’m trying to sort out because when I plot the graph there’s no variation and it gives a straight line. It should exactly be like the second picture Alistu has attached.the BER decreasing with increase in power. Is there anything wrong with the system or I’m not able to set the parameters correctly? But the system gives good Q factor and BER and eye diagram.

[alistu]

Hi Shahbaz, As I have asked you for several times, could you please specifically tell me how to choose the Received power in order to be able to plot it vs the BER? This way I can see your plot first before I give any opinion about what the problem in your system might be. Thank you and I am waiting.

[Damian Marek]

When the BER fluctuates randomly like that it is most likely due to the short sequence length. I simulated your project with a change to the Sequence length to 4096. The plot is what I get attached. The BER drops as the input power increases. There should be a minimum for the BER because of SPM, but for this short of a fiber you need much more power.

Cheers!

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