Influence of modulation formats on FWM noises in FDM optical fiber transmission systems

In this paper, we focus on the fact that FWM noises are closely related to modulation formats and frequency allocations. To reduce FWM noises in FDM optical fiber transmission systems, FWM noises are analyzed for ES, RUS, ERUS, and URUS with modulation formats such as non-return-to-zero (NRZ), random return-to-zero (RZ), differential phase-shift keying (DPSK), and bit-phase arranged RZ (BARZ). It is found that FWM noises are lowest in URUS with BARZ.