Candidate modulation schemes for next generation-passive optical networks (NG-PONs)

Various approaches have been developed for next generation passive optical networks (NG-PONs) in order to achieve higher data rates, larger counts of wavelength channels, and longer fiber ranges. Several modulation formats together with electronic based digital signal processing (DSP) implementations have been investigated in order to optimally design an access optical network. Besides increasing data rates, this new trend also plays a major role in reducing the cost and increasing the flexibility of NG-PON. In this paper, we survey the main promising modulations and DSP technologies for NG-PON. This includes modulation and optical OFDM schemes enumerate QPSK, MQAM, MSK, and multilevel based OFDM schemes. We discuss the different characteristics of these technologies showing most important contributions and challenges toward high performance cost-effective next generation access networks.