Adaptive loading algorithms for IMDD optical OFDM PON systems using directly modulated lasers

A detailed study on the effectiveness of three proposed optical orthogonal frequency-division multiplexing (OOFDM) adaptive loading algorithms (ALAs) is conducted, addressing, for the first time, a number of crucial issues related to OOFDM directly modulated laser-based intensity-modulated and direct-detected passive optical networks (PONs). The ALAs include the power loading (PL), bit loading, and bit-and-power loading (BPL) algorithms. It is shown that in comparison with the most sophisticated BPL algorithm, the simplest PL algorithm is effective in escalating a single-channel OOFDM PON performance to its maximum potential. On the other hand, for multi-channel OOFDM PON and when employing a large number of subcarriers and high digital-to-analog/analog-to-digital converter sampling speed, the BPL algorithm should be adopted. The utilization of the three ALAs can also extend the optimum clipping ratio range up to at least 3 dB compared to a conventional identical modulation scheme.