Abstract An all-optical modulation format conversion scheme from star-QAM to ASK and PSK signals is proposed by employing four-wave mixing (FWM) in highly nonlinear fibers. The phase modulation information of star-QAM signal is firstly converted to the PSK format by a degenerate FWM process under gain saturation, and then the amplitude modulation information of star-QAM signal is mapped into the ASK format by means of a non-degenerate FWM associated with the resulting PSK signal. The detailed signal processing is presented by theory and simulation. As examples, the bit-error-ratio performances of 8QAM and 16QAM signals are evaluated by a non-degenerate FWM-based aggregation scheme for ASK and PSK formats.