高速光纤传输系统中不同调制码型下的带内四波混频

带内四波混频是传输速率大于10Gb/s的光纤传输系统中最主要的非线性效应之一，它对信号传输的影响体现在两方面：使“1”码产生幅度抖动,在“0”码处产生“影子”脉冲。其结果是使信号眼图恶化，误码增加。从物理本质出发，详细的分析了带内四波混频的产生机理，在此基础上，比较了归零码、载波抑制归零码和交替反转码对“影子”脉冲的抑制能力，结果表明：交替反转码对“影子”脉冲的抑制作用最好，载波抑制归零码居中，归零码抑制能力最弱。通过数值仿真对理论分析的结论进行了验证。所得的结论可作为设计高速光纤传输系统的参考。

Intrachannel four-wave mixing in high speed optical fiber transmission systems with different modulation formats

Intrachannel Four-Wave Mixing (IFWM) is one of the most important nonlinear effects in optical fiber transmission systems with a bit rate higher than 10Gb/s. It induces the timing jitter to ‘1’ pulses and produces ‘ghost’ pulses to ‘0’ pulses, which will worsen the eyediagram and result in a bit error. In this paper, the mechanism of IFWM is analyzed in detail. And the abilities of return-to-zero (RZ), carrier-suppressed return-to-zero (CSRZ), and alternate mark inversion (AMI) to suppress the ‘ghost’ pulse induced by IFWM are theorectically compared. The results show that the AMI code is the most effective one in suppressing the ‘ghost’ pulse, CSRZ is the moderate one, and the RZ code is the poorest one. Numerical simulation is utilized to validate the conclusion. The conclusion is a good reference for designing of high speed optical fiber transmission systems.