Characterization and compensation of induced non-linear phase offset in multicarrier optical systems based on clustering techniques

Multicarrier optical systems are expected to allow data transmission above 100 Gbps in the next generation long-haul optical networks with a minimum spectral separation between carriers to increase spectral efficiency. Nevertheless, closely separation between optical carriers cause Interchannel interference (ICI) due to the inherent non-linear effects associated to optical fiber such as self-phase modulation (SPM) and cross-phase modulation (XPM). Both SPM and XPM induce a phase shifting in transmitted frequency multiplexed signals. This phase shifting can be observed as a rotated constellation diagram of phase-modulated signals and it degrades system performance by increasing the Bit-Error-Rate (BER). In this paper, a phase offset estimation and compensation using k-means clustering algorithm is validated by simulation in a multicarrier optical system. The optical carriers are modulated in PSK and 16-QAM formats at 32 Gbaud and signal transmission is simulated over standard single-mode fiber (SSMF). System performance is analyzed as a function of frequency carrier spacing and transmission distances. After Phase correction a decrease of the BER is achieved, demonstrating the feasibility and robustness of the proposed clustering technique to compensate induced nonlinear constellations rotations in future multicarrier optical networks.