You may go through the following MATLAB documentation to learn about programming OFDM modulation using MATLAB:
This documentation contains five examples that go through step by step from the introduction of OFDM to OFDM with FFT. So, you can refer to it to get a good idea of programming OFDM modulation.
While both OFDM and Flip OFDM share similar steps in modulation, Flip OFDM includes additional steps to handle the non-negativity constraint of optical signals by flipping and unflipping the signal components. So, for flipping the signal components, you can employ the ‘flipud’ function. You can leverage the following MATLAB documentation to learn more about the ‘flipud’ function:
Hope this resolves your query.