互联网业务的迅猛增长，促使光网络向大容量高性能方向发展，波分复用（WDM）与时分复用（OTDM）相结合，将是未来超高速大容量光子网络的发展方向。全光非归零（NRZ）到归零（RZ）码型转换技术，是构建这种WDM/OTDM混合网络的核心接口技术之一，它能将分别采用WDM与OTDM技术的不同网络部分有机结合，实现不同调制格式的数据在网络的不同区域之间自由传输。综述了全光NRZ到RZ码型转换技术的最新研究进展，详细分析了每种方案的工作原理，性能特征及关键技术，对比了其优缺点，指出了目前存在的问题，最后对其发展前景进行了展望。

With the rapid growth of internet business, optical networks will require better performance and higher capacity. Future optical networks are likely a hybrid of wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM) by combining the advantages of both technologies. All-optical non-return-to-zero (NRZ) to return to zero (RZ) format conversion, which can enable data with different modulation format to transmit in different region of network freely, is one of the key interface techniques of constructing this hybrid network. The research progress of all-optical NRZ to RZ format conversion is introduced. And the operation principle, characteristics, performance are analyzed in detail. Also the advantages and disadvantages of these methods are listed. Finally, the future development is prospected.