基于光子晶体光纤中四波混频效应的单到双非归零到归零码型转换

All-optical format conversion from non-return-to-zero to return-to-zero based on four-wave mixing in photonic crystal fiber

归零(Rz)码与非归零(NRZ)码是波分复用和时分复用系统中广泛采用的两种码型,全光NRZ到RZ码型转换能完成从波分复用到时分复用的网络接口功能,是未来透明光子网络中一项重要的全光信号处理技术.提出并实验证实了一种基于色散平坦高非线性光子晶体光纤中四波混频效应的单到双NRZ到RZ码型转换方法,将一束信号光与同步时钟脉冲同时输入色散平坦高非线性光子晶体光纤中,通过四波混频过程,产生两个携带该数据信息的闲频光。从而实现了单到双的NRZ到RZ码型转换功能,码型转换器工作波长在193 nm范围可调谐,最大转换效率为-21 dB,最优消光比和品质因子分别为11.9 dB和7.2.该方法的特点在于基于光纤中的四波混频效应工作,因而具有对调制格式和比特率透明的优点,同时,光子晶体光纤特有的高非线与色散平坦性,既避免了使用传统光纤需要较长的长度,又避免了波长设置不灵活的弊端,并具备可进一步增加带宽的能力,且在码型转换的同时,实现了波长转换,完成了双通道波长组播功能.整个系统为全光纤设计,结构简单,性能可靠,并易于与现有的光纤通信系统相容,对促进超高速大容量光子网络的发展具有重要意义.

The conversion from all-optical non-return-to-zero（NRZ） to return-to-zero（RZ） format is a crucial technology in interfacing WDM and OTDM of future transparent photonic network.The conversion from all-optical single-to-dual NRZ to RZ format conversion is presented and experimentally demonstrated based on four-wave mixing（FWM） in a 50 m dispersion-flattened highly-nonlinear photon crystal fiber（DF-HNL-PCF）.The original NRZ format is converted into RZ format by injecting synchronized clock signal into the DF-HNL-PCF.The FWM effect generates two sideband components,which carry the same data information as the original NRZ signal with RZ format.The proposed format converter has a wide and tunable operation wavelength range of 19.3 nm.The optimum conversion efficiency,extinct ratio and Q factor are -21 dB,11.9 dB and 7.2,respectively.The system is transparent to both bit rate and modulation format.The advantage of this scheme consists in the ability of bandwidth scalable due to the fact that the dispersion flattening of HNL - PCF is used.Furthermore,it is all optical fiber,compact and robust,which makes it more competitive as well as easily accessible for use in practical optical communication systems.