Optisystem OFDM Block

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

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

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!

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.

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