256-QAM Interleaved Single Carrier FDM for Short-Reach Optical Interconnects

In this letter, we experimentally demonstrated a 40-Gbit/s 256-quadrature amplitude modulation (256-QAM) interleaved single-carrier frequency-division multiplexing (I-SC-FDM) over 10-km standard single-mode fiber (SSMF) for optical interconnects. I-SC-FDM has lower peak-to-average power ratio and lower computational complexity of transmitter compared with orthogonal frequency division multiplexing (OFDM). High-level QAM can achieve high spectral efficiency; however, it is susceptible to both linear and nonlinear distortions. The frequency-domain one-tap equalizer and the time-domain decision-feedback equalizer with recursive least square and Volterra algorithm are jointly employed to eliminate the distortions for the 256-QAM I-SC-FDM. After 10-km SSMF, I-SC-FDM has better performance than localized SC-FDM and OFDM. Therefore, I-SC-FDM shows the potential for short-reach optical interconnects.