High-Speed PDM-RZ-8QAM DWDM Transmission (160 $\times$ 114 Gb/s) Over 640 km of Standard Single-Mode Fiber

Based on the practicability issue, using the standard single-mode fiber (SSMF) in the transmission line is important for high-speed optical transmission. Here, we propose and experimentally demonstrate a 640-km SSMF-based high-speed dense wavelength-division-multiplexing (160times114 Gb/s) transmission system in 25-GHz channel spacing employing polarization-division-multiplexing return-to-zero (RZ) eight quadrature amplitude modulation format and digital coherent detection. The filtering effects for RZ and nonreturn-to-zero formats have also been probed in this investigation. For all 160 channels (1530-1560 nm, cover the whole C-band), the bit-error rate is smaller than 2times10^-3 without Raman amplification, optical dispersion compensation, and any special fiber in this straight-line slink.