C-band 56 Gbit/s on/off keying system over a 100 km dispersion-uncompensated link using only receiver-side digital signal processing

In this Letter, we present a record C-band 56 Gbit/s intensity-modulation/direct-detection optical on/off keying (OOK) system over a 100 km dispersion-uncompensated link using only the receiver-side digital signal processing (DSP). The proposed DSP mainly includes an adaptive moment estimation (Adam)-based polynomial nonlinear equalizer (PNLE), autoregression (AR)-based post filter, and maximum likelihood sequence estimation (MLSE). Due to square-law detection, chromatic dispersion induces 11 nulls on the 28 GHz spectrum of the 56 Gbit/s OOK signal after the 100 km standard-single-mode-fiber transmission. Adam-based PNLE eliminates major linear and nonlinear distortions, but it cannot compensate the nulls. After the Adam-based PNLE, the AR-based post filter and MLSE further deal with the inter-symbol interference caused by the nulls to improve the system performance. The proposed C-band 56 Gbit/s OOK system shows great potential for future metro networks and data center networks.