Dual-Polarization Non-Linear Frequency-Division Multiplexed Transmission With $b$-Modulation

There has been much interest in the non-linear frequency-division multiplexing (NFDM) transmission scheme in the optical fiber communication system. Up to date, most of the demonstrated NFDM schemes have employed only single polarization for data transmission. Employing both polarizations can potentially double the data rate of NFDM systems. We investigate in simulation a dual-polarization NFDM transmission with data modulation on the b-coefficient. First, a transformation that facilitates the dual-polarization b-modulation was built upon an existing transformation in [M. Yousefi and X. Yangzhang, “Linear and nonlinear frequency-division multiplexing,” in Proc. Eur. Conf. Opt. Commun., Dusseldorf, Germany, Sep. 2016, pp. 342344]. Second, the q
_c
-and b-modulation for dual polarization were compared in terms of Q-factor, spectral efficiency (SE), and correlation of sub-carriers. The correlation is quantified via information theoretic metrics, joint and individual entropy. The polarization-multiplexed b-modulation system shows 1-dB Q-factor improvement over q
_c
-modulation system due to a weaker correlation of sub-carriers and less effective noise. Finally, the b-modulation system was optimized for high data rate, achieving a record net data rate of 400 Gb/s (SE of 7.2 b/s/Hz) over 12 × 80 km of standard single-mode fiber with erbium-doped fiber amplifiers. Based on the aforementioned simulation results, we further point out the drawbacks of our current system and quantify the error introduced by the transceiver algorithms and non-integrability of the channel.