在高速光纤通信系统中码型的选择是决定系统传输质量和光谱效率的主要因素。码型的选择和信道速率、信道波长间隔、光放大器的选择、光放大器放置间隔、光纤的类型、色散管理策略等各种因素密切相关。分析了非归零码(NRZ)、归零码(RZ)和载波抑制归零码(CS-RZ)码型的产生方式及特点。采用单信道和掺铒光纤放大器(EDFA)放大方式对三种码型进行了40 Gb/s的100 km G.652光纤通信传输实验。比较了三种码型的系统传输特性、最佳入纤功率和不同入纤功率下的功率代价:载波抑制归零码最佳入纤功率为9 dBm,功率代价小于非归零码和归零码。结果表明,在相同的色散补偿条件下,载波抑制归零码比归零码和非归零码有更优的非线性容忍度。

The signal modulation format is a key issue for high speed fiber optical communication system, which determines transmission quality and spectral efficiency. The choice of the signal optical modulation format is affected by the facts such as channel data rate, channel wavelength spacing, optical amplifier, optical amplifier span, fiber dispersion and nonlinear parameter, dispersion management strategy, and so on. The generation schemes and characteristics of nonreturn-to-zero (NRZ), return-to-zero (RZ) and carried-suppressed return-to-zero (CS-RZ) are described in this paper. The 40 Gb/s single channel transmission over 100 km G.652 fiber with erbium-dope fiber amplifier (EDFA) is done for these three formats. The best launched power and power penalty in different fiber-input power for each format are investigated: the best launched power for CS-RZ is 9 dBm, its power penalty is smaller than the others. It could be shown that CS-RZ format offers higher nonlinearity tolerance than the NRZ and RZ formats with identical dispersion compensation scheme.