400-Gbit/s Net Rate DP-OFDM Signals Fiber-THz-Fiber Seamless Transmission Employing Hybrid Time-Frequency-Polarization Domain Equalization

The integration of photonic terahertz (THz) wireless and optical fiber links combines the advantages of ultra-long distance, low-loss, and high-capacity transmission of fiber link with the advantages of flexible, seamless transmission of THz wireless link. Compared with single-carrier (SC) modulation, orthogonal frequency division multiplexing (OFDM) modulation technology has higher spectral efficiency and exhibits robustness against dispersion in optical fiber transmission, effectively alleviating multi-path effects in wireless communication. In the study, we experimentally demonstrated an OFDM fiber-THz-fiber seamless communication system. Utilizing dual-polarization (DP) technology to double the system capacity. Probabilistic shaping (PS) technology is used to adapt transmission rate and improve system capacity under a limited SNR. Finally, we propose a 2×2 multiple-input and multiple-output (MIMO) hybrid time-frequency polarization domain (TFPD) Volterra nonlinear equalization (VNLE) algorithm, aiming to simultaneously address both linear and nonlinear impairments in the time-domain, frequency-domain, and polarization-domain. The 50-GBaud PS-64QAM DP-OFDM signals are successfully delivered over two spans of 20-km SSMF and 3-m wireless distance at 320 GHz, achieving a net rate of 400 Gbit/s thanks to the MIMO TFPD-VNLE.