四値ビット位相RZ信号を用いた周波数多重光ファイバー通信システムにおける四光波混合雑音の低減(超高速伝送・変復調・分散補償技術,超高速光信号処理技術,広帯域光増幅・WDM技術、受光デバイス,高光出力伝送技術,一般,(ECOC報告)) Reduction of Four Wave Mixing Noises in FDM Optical Fiber Transmission Systems with Quaternary Bit-Phase Arranged RZ

In long-haul FDM optical fiber transmission systems, transmission characteristics are degraded by four-wave mixing (FWM) in optical fibers. To overcome this problem in equally-spaced (ES) allocations, modified repeated unequally-spaced (RUS) allocations such as equally-spaced RUS (ERUS) and unequally-spaced RUS (URUS) allocations have been already proposed as frequency allocations and examined. FWM noises are also closely related to 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), and it has been already found that FWM noises are lowest in URUS with BARZ. In this paper, to reduce FWM noises further, quaternary BARZ (Q-BARZ) is proposed as a modulation format, and FWM noises are analyzed. It is found that FWM noises with channel frequencies vanish in RUS, ERUS, and URUS with Q-BARZ.