Optimization of OFDM parameters for 10-Gbps long reach coherent PONs

Coherent passive optical networks (PONs) employing orthogonal frequency division modulation (OFDM) have emerged as a promising candidate for the implementation of future long-reach high-capacity optical access infrastructure. In addition to the improved receiver sensitivity, coherent systems allow advanced vectorial modulation formats and, thus, make a more efficient use of the spectrum. Mitigation of the phase noise, however, is still a challenge that must be addressed in low-cost access systems. In OFDM systems, in particular, pilot-aided equalization can be employed to efficiently combat this impairment. In this work, we present extensive simulation results to optimize a 100-km LR-PON with 10-Gbps capacity in terms of the number of subcarriers and pilots, as well as the relative power of the pilots. These results reveal that 64 subcarriers, being 10 of them pilots, and a relative amplitude of 1.8 leads to a BER of 4.736×10-4.