Phase modulation-enabled transmission performance improvement and parameter-relaxation of DACS/ADCS in SMF-based IMDD optical OFDM systems

Adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM) using phase modulation (PM) (AMOOFDM-PM) is proposed and theoretically explored, for the first time, in intensity modulation and direct detection (IMDD) single-mode fibre systems. AMOOFDM-PM utilises an electrical OFDM signal to modulate the phase of a RF carrier prior to performing optical intensity modulation. Compared to conventional AMOOFDM based on amplitude modulation, AMOOFDM-PM can not only significantly lower the minimum requirements on quantization bits and sampling rates of digital-to-analogue /analogue-to-digital converters, but also simultaneously considerably improves the signal transmission performance. In addition, AMOOFDM-PM also shows excellent system flexibility and performance robustness to variations in transmission link characteristics.