Single-span transmission of WDM RZ-DPSK signal over 310-km standard SMF without using FEC and remote-pumping

To avoid significant stimulated Brillouin scattering (SBS) generation in a bidirectional Raman-pumped long single-span transmission system, the SBS threshold is studied in both return-to-zero on-off -keying (RZ-OOK) and RZ differential phase-shift keying (DPSK) systems. It shows that SBS threshold in an RZ-DPSK system is more than 10 dB higher than that in an RZ-OOK system, and SBS reflection is dominated by copumping, while counterpumping has minor effect. Error-free eight-channel single-span transmission is demonstrated over 310-km standard single-mode fiber using RZ-DPSK format and bidirectional Raman pumping, without applying forward-error correction and remote-pumping techniques.