超大传输容量少模多异芯光纤的实现机理及方法研究

The rapid growth of multi-media and data rich applications has driven the bandwidth demand for long-haul fiber-optic links at unprecedented rates. Against this background, time division multiplexing, wavelength division multiplexing, polarization division multiplexing and multi-level modulation make the transmission capacity of single-mode fiber approach the Shannon limit. Space division multiplexing (SDM) technology can breakthrough this limit and provide a solution for the capacity increase in the future. At present, related to the research of SDM, domestic and international researchers are focusing on multi-core fiber (MCF) or few-mode fiber (FMF). However, further increasing core number of MCF or mode number of FMF will cause the failure of fiber fabrication or complicate the process of multiplexing and demultiplexing. This project is planned to propose a kind of heterogeneous trench-assisted few-mode multi-core fiber which combines MCF with FMF and the key issues in the research include: 1) Theoretical analysis method for mode coupling coefficient between heterogeneous trench-assisted cores, 2) Design and optimization of cores with low differential mode delay and large effective area, and 3) Design and optimization of core deployment in the cladding. The results will help further increase the transmission capacity of optical fiber, decrease the inter-core crosstalk and reduce the differential mode delay in order to break through the limit of transmission capacity, actualize the higher multi-level modulation formats and reduce the computing complexity of the digital signal processing at the receiver end.

在多媒体和数据应用程序快速扩展以及驱动骨干网带宽需求量迅速增长的网络背景下，时分、波分、偏分复用技术与多级调制方式使得大容量传输系统中单模光纤容量快速接近香农理论极限。空分复用技术(SDM)可以突破该限制，为未来光纤容量增长提供新的解决方案。目前，国内外研究者关于SDM的研究多集中在多芯光纤(MCF)或少模光纤(FMF)，但进一步增加MCF纤芯或FMF模式的数量会导致光纤制造失败或模式复用与解复用过程复杂化等问题。本项目结合MCF和FMF提出一种沟槽协助式少模多异芯光纤，拟研究的关键问题包括:1)沟槽协助式异芯间模式耦合系数的理论分析方法；2)低差分模式时延与大有效面积纤芯的设计与优化；3)光纤包层中纤芯部署方式的设计与优化。项目研究成果有助于进一步扩大光纤传输容量，降低芯间串扰并减小差分模式时延，进而达到突破传输容量瓶颈，使用高阶多级调制方式以及减小接收端数字信号处理计算复杂度的目的。

空分复用(Space Division Multiplexing, SDM)为光纤传输系统提供了一个新的发展方向，有可能使系统容量增加一个数量级。SDM通过利用多芯光纤(Multi-Core Fiber, MCF)或少模光纤(Few Mode Fiber, FMF)使得多个不同空间上的模式同步传输。作为同时实现多芯和少模的超大密度空分复用(Dense Space Division Multiplexing, DSDM) 的新型少模多芯光纤(FM-MCF)是一种进一步增加传输信道提高传输容量的可靠方案。本项目深入地研究了超大密度空分复用技术(DSDM)，并针对FM-MCF展开了系统的设计研究，同时也研究了相关基础科学问题。此外也围绕光纤结构，研究了其他一些新结构新材料和新特性的光纤。研究内容主要包括：1）模式耦合系数的理论分析方法研究与优化；2）低差分模式群时延的3模12芯光纤；3）沟槽/低折射率棒辅助的低串扰多芯光纤；4）方点阵式沟槽/低折射率棒辅助32异芯光纤；5）有效的纤芯选取方法；6）纤芯排列方法讨论；7）基于多芯光纤的模式复用/解复用器；8）面向中红外的硫化物反谐振光纤。依托本项目，共发表学术论文15篇，其中SCI收录6篇，EI收录9篇；申请专利2项；参加国际学会9人次；培养博士后出站1名，培养研究生7名。