140-Gb/s PS-256-QAM Transmission in an OFDM System Using Kramers–Kronig Detection

We experimentally demonstrate an orthogonal frequency-division multiplexing (OFDM) system with direct detection. Adopting Kramers-Kronig (KK) detection and probabilistic shaping (PS) technology, 140-Gb/s 256-QAM signal can be successfully transmitted over 25-km standard single-mode fiber (SSMF), which satisfies the normalized generalized mutual information (NGMI) threshold of 0.865. Based on the experimental results, the performance of single-side band (SSB) OFDM signal can be effectively improved with the aid of KK detection and can be further enhanced by the deployed PS method.