中文摘要：

码型转换是实现非归零（NRZ）信号全光时钟恢复的关键技术．提出了一种基于折叠式超快非线性干涉仪的全光NRZ到伪归零（PRZ）信号转换的新型方案．基于半导体光放大器的分段模型和超快非线性干涉仪的传输函数，建立了该方案的理论分析模型，数值模拟了不同速率下的码型转换过程．实验实现了稳定的10，20和40Gbit／s的NRZ到PRZ信号的码型转换，分析了影响码型转换输出特性的因素，理论分析结果与实验结果基本符合．

英文摘要：

Pattern conversion is the key technology for all-optical clock recovery from non-retum-to-zere （NRZ） signal. A novel scheme for all-optical NRZ to pseudo-return-to-zero （PRZ）conversion using a folded ultrafast nonlinear interferemeter （UNI） has been put forward and demonstrated for the first time. Based on the segmented semiconductor optical amplifier model and the transmittance of the UNI, theoretical model for this scheme is established and the output characteristics are calculated theoretically. Stable format conversion from NRZ data to PRZ data has been achieved at 10, 20 and 40 Gbit/s. The influences of the input signal characteristics on the performance of the format conversion are investigated. Experimental results are in agreement with the numerical simulation results.