Optisystem OFDM Block

[alistu]

Is there any way to create an OFDM block in Optisystem?
I know it is available in optisystem newer versions but since you cannot access inside the block, I would like to know how to create one.
In particular, I need to simulate the subsystem shown in the attached file.
Thank you in advance.

[Jaffar Emad Kadum]

You can design OFDM system using MATLAB and then import the data into OPTISYTEM

[alistu]

Thanks, but I particularly would like to know if Optisystem has that capability itself.

[Damian Marek]

Unfortunately, if you want to build your own OFDM modulator you will have to use Matlab. It is not possible to build it from baser components.

However, in our next update for OptiSystem we are improving the functionality of the OFDM components including the capability to modulate different carrier ranges with different modulation formats., including dispersion compensation and training and pilot symbols. If any of those features interest you let me know.

Regards

[ELAARAIND M]

sir,we need help about the attached file.In which we have send the downstream ,we have got output in ONU.but upstream not work .sir/madam any one give us solution. thank u

[ELAARAIND M]

sir,while simulating the OFDM Ccoherent or direct detection .osd file .In output q-factor is 10^49 ,BER is o .Is it correct ?.we are using this into our project (WDM/OFDMA PON SYSTEM)the result is same .is it correct ?But we cannot able to send upstream data .

[alistu]

Thank you. All these features are really interesting actually, but it’s a good thing to know for sure the current version doesn’t have that capability so that I concentrate better on using matlab for the time being.

[alistu]

So far I have written a basic Matlab OFDM program. It runs in Matlab without any errors. But when I use it in the Optisystem Matlab component and run the simulation, I have to force close the program after a few seconds although it doesn’t give any errors or something in the due box. I think the problem is due to the incorrect use of input/output signal formats even though I have tried to make the codes according to the Matlab component tutorial pdf files and videos. My M-file is attached here. The program is really simple and adequate comments so as to make it be understood even more easily have been added. I just want to know why the aforementioned problem occurs. Can anyone help?

[Damian Marek]

Yes I don’t think that you have set up the proper OutputPort1 data structure. Typically the best way to start is with:

OutputPort1 = InputPort1;

To set it up exactly the same as the input, however you will need to make changes as your input is a M-ary signal and your output is an electrical signal. Although I probably already mentioned it we have videos about the Matlab component here:

Matlab Binary Switch

It shows you how to view the data structures in Matlab and setup the input/output ports.

Regards

[alistu]

I have already watched the two vids and studied the three tutorials, but all of them are about situations with the same input and output data structures. That is why I can’t find the solution to my problem in them.

What you mentioned about the code “OutputPort1 = InputPort1;” is also valid only in those situations. Therefore, the problem is still there.

[Damian Marek]

Correct, but using the same procedure you could say create a second electrical “dummy” input and copy it to the output or view it in the work space to copy the data structure.

The pdf here:

https://cdn.optiwave.com/wp-content/uploads/2014/03/31095858/Matlab-Electrical-Example.pdf?76994c

Outlines the data structure, but personally I find it easier to just view it directly in Matlab and play around with it. It might also be helpful if you are not familiar with Matlab data structures to read their help on the subject:

http://www.mathworks.com/help/matlab/ref/struct.html

You can learn the syntax for accessing and creating data structures there as well.

Cheers!

[alistu]

I appreciate your help Damian. I modified the Matlab codes the way you told me. Now while simulating, there comes an error stating there is a problem with output signal type. This is not a problem I can solve just by being familiar with Matlab. It concerns having a deep understanding of how the Opti vector system works, which is not unfortunately given by the available tutorials. Is there any way I can import the Optisystem OFDM block into Matlab? Or perhaps contanct the Optisystem programmers? Thank you.

Here I have attached both my modified .M file and Optisystem block diagram with Matlab component.

[Damian Marek]

Hi Alistu,

In the attached project file and m-file I made changes to create a working electrical output. I simply added a new “dummy” input with a random electrical sequence, which sets up a proper data structure that you can then modify with the M code. I set the output ports equal to this input and the simulation runs well.

Unfortunately, I do not think the OFDM component you wrote is working 100% because I do not understand the output.

[alistu]

It doesn’t take much time from anyone who has ever worked with Matlab component to just take a look at the files and find my mistake, yet it’s a great help to me. I have attached the due files to my former reply. Thanks.

[alistu]

Thank you Damian. You’re right. It doesn’t work at all (There is NO SIGNAL in the output)!
BTW, is there any way I can download the two files named “MatlabOptiSysBER.m” and “OpticalLinkProject.osd” introduced in the link below:

Matlab Cosimulation

[alistu]

I would also like to know what “position array” is in OptiSystem OFDM block. There is no such thing in any OFDM book.

In OFDM, the number of subcarriers and FFT points are the same in reference books. How come these two are different in here? I don’t think reproduction of OptiSystem OFDM results by using Matlab component would be possible when there is little information about how Optiwave engineers have written its program.

Thanks for any help in advance.

[Damian Marek]

Hello,

I’ll preface this explanation with the warning that recently there was a large update to the OFDM components and now the parameter Position Array is gone. The OptiSystem team added a lot of functionality to the OFDM components as well.

In the recent past, the component functioned in the following fashion. Setting the Number of FFT points sets the total number of available (not necessarily used) sub-carrier positions centered at DC or 0 Hz. The number of sub-carriers would then set the total number of sub-carriers actually used (for example 4 sub-carriers might be used for a QPSK format). The position array then sets the starting point of the range of the sub-carriers used.

For example, if I set the Number of FFT points to 32 and set the position array to 16 with number of sub carriers set to 4. The sub-carriers used will be 16, 17, 18, 19, which corresponds to 0 Hz, 1.25 GHz, 2.5 GHz, 3.75 GHz (these frequencies are calculated from a Bit rate of 10 Gbps and 4-QAM modulation).

These options were found to be not entirely transparent for users and that’s why it was changed.

Regards

[Ajay Vyas]

You can design your own OFDM block by using the QAM modulator & M Ary Block.

[alistu]

first of all, thanks for your answer.
Do you mean without the use of MATLAB component? How would you make orthogonal signals that should be made by FFT or WT? I have used matlab component to build the block and have also used Matlab codes for the M-ary modulation.

[ELAARAIND M]

MR.Ajay Vyas thank u for ur reply.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 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

[–]

Hi everybody,
Could you find the solutions to the problems you discussed above? Was the implementation using the code outline that was attached most recently in the above discussions successful?
Please reply.
Thank you

[alistu]

Hi Gokul,

The above files don’t work fine, but they might give you information on how to design your own block. I am currently using Optisystem OFDM components: https://optiwave.com/forums/topic/ddo-ofdm-with-os12-ofdm-components/ .

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