Reduced-Guard-Interval OFDM Using Digital Sub-Band-Demultiplexing

The overhead of cyclic prefix (CP) in coherent optical OFDM (CO-OFDM) tends to be too large for high-speed and long-haul optical fiber transmissions. We discuss and experimentally demonstrate a transmission of reduced guard interval OFDM (RGI-OFDM) with much reduced CP overhead based on digital sub-band demultiplexing. The proposed techniques are used to process a 66.7-Gb/s RGI-CO-OFDM signal ( ~ 20-GHz bandwidth) after 5440-km fiber transmission. The experiments show that it can reduce the overhead from 36.7% to 12.5%. We also optimize the digital signal processing in the filter bank for a better performance.