面向高阶编码格式的全光波长变换技术的研究

Wavelength conversion is of great importance in solving the problems in optical networks, such as wavelength mismatch, wavelength reuse, virtual wavelength route, all-optical wavelength switching. Wavelength conversion for high-order coding formats is an urgent need in order to adapt to the current mainstream transmission technology. Considering the shortcomings of the wavelength conversion based on the four wave mixing, including low conversion efficiency, adjacent frequency crosstalk, phase matching difficulty, this project proposes a new wavelength conversion technology for high-order coding formats. The technique is based on the principle of SOA cross phase modulation. The effect of the cross gain modulation is overcome by using the differential balanced signal. A all-optical phase modulator to break through the current electro-optic modulator rate limit is put forward. New schemes of optical wavelength converters are proposed for DPSK, QPSK, DP-QPSK, QAM and other high-order coding formats. It can convert more than 40Gb/s signals and can be used in 100G and above systems. Scientific problems, such as the rate limit of SOA cross phase modulation under the control of balanced differential signal, the quality evaluation of high-order coding formats through the all-optical wavelength conversion, the effects of the link fiber nonlinearity and other SOA nonlinearity on wavelength conversion, will be solved. The wavelength conversion technology has many advantages, such as high conversion efficiency, having a gain, small in size and easily integrated. It has important application prospects in all-optical wavelength switching networks.

波长变换对于解决光网络中的波长失配、波长重用、虚波长路由以及全光波长交换等问题有重要意义。面向高阶编码格式的波长变换是适应当前主流传输技术的迫切需要。本项目针对基于四波混频波长变换的转换效率低、邻频串扰、相位匹配难等缺点，提出了一种新型面向高阶编码格式的波长变换技术。该技术基于SOA的交叉相位调制原理，采用差动平衡信号克服交叉增益调制的影响，拟实现突破当前电光调制器速率极限的全光相位调制器，提出了面向DPSK、QPSK、DP-QPSK以及QAM等高阶编码格式，能转换40Gb/s以上信号，适于100G及以上系统使用的全光波长变换器的新结构。拟解决平衡差动信号控制下的SOA交叉相位调制的速率极限、高阶编码格式经过全光波长变换后的质量评价、链路光纤非线性和SOA其它非线性对于波长变换的影响等科学问题。该波长变换技术具有转换效率高、有增益、体积小、易于集成等优点，在全光波长交换网中有重要应用前景。

本项目“面向高阶编码格式的全光波长变换技术的研究”的目的是基于SOA的交叉相位调制原理，采用差动平衡信号克服交叉增益调制的影响，突破目前SOA交叉相位调制的速率极限、解决高阶编码格式经过全光波长变换后的质量评价，以及链路和SOA非线性对波长变换影响等科学问题。研究了探测光、控制光和偏置电流对SOA调制效果的影响，提出了SOA工作点的优化方法和原则。提出了用光纤斐索干涉仪测量交叉相位调制产生的非线性相移的实验方案，并给出了测量公式。提出并研制了基于MZ干涉仪和3X3耦合器2种差动平衡信号产生单元。利用两个串联SOA消除了交叉增益调制效应，实现了SOA交叉相位调制和波长变换的实验方案。提出使用四元数方法描述和分析偏振态，证明了“保偏光纤中由多重偏振效应引起的双折射合成满足矢量叠加原理”，还证明了通过光纤上邻近3点的3个Stokes矢量可以计算得到这段光纤的偏振模耦合系数。研究了DWDM系统中EDFA串扰引起误码率问题，给出了误码率的计算公式，讨论了影响误码率的因素，并进行了实验验证。研究了涡旋光束经菲涅尔波带片传输时的衍射特性，涡旋光束经粗糙表面传输时的散斑特性及粗糙度的测量。本项目研究工作不仅可以促进波分复用光通信系统和光交换网络的发展，对提高网络的可靠性、可扩展性和自愈性也具有重要意义。