Spectrally Efficient 168 Gb/s/λ WDM 64-QAM Single-Sideband Nyquist-Subcarrier Modulation With Kramers-Kronig Direct-Detection Receivers

Due to their simple and cost-effective transceiver architecture, single-polarization and single-photodiode-based direct-detection (DD) systems offer advantages for metropolitan area network and data-center interconnect applications. Single-sideband subcarrier modulation (SSB SCM) signaling with DD has the potential to achieve high information spectral density (ISD) but its performance can be significantly degraded by signal-signal beat interference (SSBI). The recently proposed Kramers-Kronig (KK) digital signal processing scheme is effective in eliminating the SSBI penalty. Through the use of the KK scheme, we achieved 4 x 168 Gb/s wavelength division multiplexing DD SSB 64-QAM Nyquist-SCM signal transmission over 80 km of uncompensated standard single-mode fiber at a net ISD of up to 4.61 (b/s)/Hz. The joint optimization of the optical carrier-to-signal power ratio and the KK algorithm sampling rate is described.