While we are talking about fun facts of the Fourier transform, the transfer function of the DFT is a sinc. That's how OFDM works, it performs an FFT on parallel input symbol streams. If you look at the spectrum of your signal it's sinc (approximately because they are truncated) channels spaced at 1/symbol rate which don't exhibit (theoretically if they weren't truncated) any interchannel interference.

It's going from the frequency domain (parallel symbol streams) to the time domain (multi-carrier RF), so it's using the inverse FFT.