光的8-DPSK调制格式是一种新型光调制格式。它具有较窄的频谱宽度, 较高的频谱利用率, 近似恒定的包络特性, 同时能够较好地抑制光纤的非线性效应。根据8-DPSK的基本原理, 仿真分析了8-DPSK信号的调制和解调, 建立了8-DPSK的仿真系统。在此基础上, 研究了将8-DPSK调制格式应用于偏振模色散补偿系统的性能。从理论和数值上分析了不同占空比下8-DPSK信号的偏振度(DOP)和偏振模色散(PMD)的关系。结果表明, 不同占空比下, 信号的频谱结构不同, 因而DOP灵敏度不同。在PMD补偿系统中, 由于采用DOP作为反馈信号, 因此不同占空比的8-DPSK信号, 其补偿效果不同。通过数值仿真分析得出, CSRZ-8-DPSK信号由于其较窄的频谱宽度和载波抑制的特性, 是最具前景的调制格式。

The optical 8-DPSK is a new modulation format. It has narrower spectrum structure, higher spectrum efficiency, nearly invariable envelope, and better nonlinearity suppression characteristic. According to the principle of 8-DPSK, the modulation and demodulation in the back-to-back system of 8-DPSK is analyzed via simulation. Moreover, the polarization-mode dispersion compensation performance of 8-DPSK is studied. The relationship between the signal’s degree of polarization (DOP) and polarization-mode dispersion (PMD) of different duty-cycle signals is analyzed theoretically and numerically. The result shows that the DOP sensitivity is different among different duty-cycle signals, because the change in duty-cycle results in the change in spectrum structure. In the polarization-mode dispersion compensation system, DOP is adopted as the feedback signal, therefore, the performance of compensation is different among different duty-cycle signals. Through simulation analysis, CSRZ-8-DPSK has the best compensation performance thanks to its narrower spectrum structure and carrier-suppressed characteristic.