I'm a french student in engineering and I'm given a kind of mandatory technical project to work out on until February.
I must investigate the following article : https://www.osapublishing.org/DirectPDFAccess/C41EF419-AD7D-EDF3-A173E8B93A0B610C_350066/oe-24-19-22110.pdf?da=1&id=350066&seq=0&mobile=no and implement the same kind of iterative algorithm on MATLAB.
Actually I'm not good at signal processing either that much, only have the basics, however I don't understand why they say "the inherent frequency interval limit (of fFT) can be overcome using discrete Fourier transform". In my opinion that is non-sense because fFT is basically just the same as dFT, you just have to sum the sampled values an other way with their odd and even indexes. Therefore I don't really understand what do they apply dFT for...
If someone could help me please he would be more than welcome !