1.6-b/s/Hz 6.4-Tb/s QPSK-OCDM/WDM (4 OCDM x 40 WDM x 40 Gb/s) transmission experiment using optical hard thresholding

A record of 1.6 b/s/Hz spectrum efficiency is achieved in an optical code-division-multiplexing (OCDM)/wavelength-division-multiplexing (WDM) link by quaternary phase-shift keying optical encoding/decoding along with ultrafast optical time-gating and optical hard thresholding in addition to polarization multiplexing. As a result, a transmission of 6.4 Tb/s OCDM/WDM (4 OCDM /spl times/ 40 WDM /spl times/ 40 Gb/s) using only the C-band wavelength region is experimentally demonstrated.