Range extension in coherent OFDM passive optical networks using an inverse Hammerstein nonlinear equalizer

High-speed demand driven by bandwidth-consuming applications, such as video streaming and cloud computing, is exceeding available network capacity, forcing operators to implement innovative technologies to increase the throughput offered to end users. In particular, passive optical networks (PONs) with a full-duplex capacity of 10 Gb/s over a 40-km span are expected to be developed shortly. However, the range of such systems is severely penalized due to fiber and splitter losses. To increase the transmission distance of PONs, coherent optical (CO) communications have regained attention. Orthogonal frequency division multiplexing (OFDM) has been proposed as a modulation format due to its robustness to chromatic dispersion, high spectral efficiency, and flexibility. The high peak-to-average ratio of OFDM signals, however, makes them very vulnerable to fiber nonlinear distortion. In this paper, we propose what we believe is a novel, low-complexity equalizer based on the inverse Hammerstein model to partially compensate for the nonlinear distortion in CO-OFDM PONs. Numerical simulations using the split-step Fourier transform method reveal a potential link increase of 20 and 5 km for bit rates of 10 and 40 Gb/s, respectively, when compared to linear equalization.