多芯光纤通信串扰及多信道拉曼放大技术研究

Progress in optical fiber communications over the recent years has been amazingly significant while we are approaching the fundamental transmission capacity limit of single mode fibers even despite the use of sophisticated modulation and coherent detection techniques and polarization multiplexing. At the same time,world traffic flow keeps growing by 40%-60% year-on-year,leading to the looming capacity crunch in the next decade or so. As the radical innovation to the physical layer of optical fiber transmission system, space-division multiplexing (SDM) based on multi-core fiber (MCF) has been known as the only remaining physical dimension that has not yet benn exploited to increase the data capacity of one single fiber. Although it can be promising to scale the capacity by another 2 to 3 orders of magnitude, extremely challenging technical issues are to be addressed, especially named as modal crosstalk and optical amplification assiciated with MCF.In response to this need, we propose to investigate the crosstalk between individual cores in multi-core fiber and to develop an all-fiber MCF based distributed Raman amplification scheme for SDM communication systems. The crosstalk will be analyzed theoretically by mode-coupling equations derived from a simplified twin-core fiber model to proceed the insight under the design parameter of MCF. Further, we will develop a finite difference time domain (FDTD) algorithm to simulate the mode profile and light propagation in MCF accurately. After evaluating the crosstalk dependence on wavelength and polarization, we propose to use the MCF core-waveguide itself as the Raman gain medium by injecting Raman pump power from the center core. The large crosstalk/power coupling in the short wavelength leads to sufficient pump light conversion to every core for efficient distributed Raman amplification for any formats of transmitted signal. The crosstalk of signal wavelength (C+L band) remains low for signal transmission. The carefully designed parameters of MCF will help to fabricate high quality MCF using stack-and-draw process. Intensive research work will be carried on the MCF sample including measurements of loss, dispersion, nonlinear coefficient, Raman gain coefficient, and birefringence, etc. Experimental work on optimization of the Raman amplifier will be done in terms of gain and noise properties. Further, we will experimentally utilize coherent detection scheme over MCF and multiple-input multiple-output (MIMO) technique to perform MIMO-based equalization hence thoroughly suppress the modal crosstalk of amplified signal wavelength for long distance SDM optical fiber transmissions. The outcome of this project will be essential for future SDM-based ultra-high capacity optical fiber transmission network.

为了克服传统单模光纤的理论传输容量极限导致的容量紧缩问题，基于多芯光纤的空分复用通信系统方案被提出以充分利用空间维度来提升单根光纤中的数据容量，但是一系列技术挑战特别是多芯之间模式耦合带来的功率串扰和在线全光放大技术的缺失成为阻碍这一技术实用化的主要瓶颈。本项目提出研究多芯光纤中的通信串扰及多信道拉曼放大技术，通过理论分析，数值仿真与实验制备克服多芯光纤中各纤芯在通信波段的光信号串扰与功率损耗难题；深入探索多芯光纤中光波串扰的波长相关性与偏振相关性问题并基于此研究多芯光纤中的分布式拉曼放大机理；通过优化的光纤设计和制备，开展多芯光纤中单芯注入多芯耦合的拉曼放大系统的理论与实验研究；最后结合数字信号均衡技术研究全光放大多芯光纤通信系统中多信道间的串扰抑制。本项目的研究成果将有助于解决通信用多芯光纤实用化的主要技术难题并推动下一代空分复用光纤通信技术的发展。

国家自然科学基金项目“多芯光纤通信串扰及多信道拉曼放大技术研究”（61205063）提出研究多芯光纤中的通信串扰及多信道拉曼放大技术，通过理论分析，数值仿真与实验制备克服多芯光纤中各纤芯在通信波段的光信号串扰与功率损耗难题；深入探索多芯光纤中光波串扰的波长相关性与偏振相关性问题并基于此研究多芯光纤中的分布式拉曼放大机理；通过优化的光纤设计和制备，开展多芯光纤中单芯注入多芯耦合的拉曼放大系统的理论与实验研究；最后结合数字信号均衡技术研究全光放大多芯光纤通信系统中多信道间的串扰抑制。本项目的研究成果将有助于解决通信用多芯光纤实用化的主要技术难题并推动下一代空分复用光纤通信技术的发展。.本项目计划在国内外核心期刊与国际会议上发表高质量论文6-8 篇，其中SCI 收录国际重要期刊3 篇以上，申请至少3项国家发明专利。.本项目执行三年以来，基本实现了项目提出的目标：采用COMSOL软件对多芯光纤进行了建模并优化；基于模式耦合理论和功率耦合理论对串扰波长相关性进行分析和建模；成功采用堆叠法和打孔法试制了多批次七芯光纤并进行了相关测试，光纤1550nm衰减均值低于0.3dB/km，芯间距均匀度优于1.0um；采用腐蚀光纤束法，制作了适用于不同芯间距规格的七芯光纤复用/解复用器；实现复用/解复用器插损均值低于1.5dB，最大值低于2dB；搭建了基于空分复用系统的多芯光纤接入网实验平台，提出了基于波长空分复用技术的新型接入网架构，下行传输速率达到300Gb/s，上行单波长速率达到20Gb/s；基于多芯光纤多径干涉现象，采用偏芯熔接方法，实现了一种温度灵敏度高，压力灵敏度低的多芯光纤温度传感器。.在本项目支持下，发表国内外高水平期刊及会议文章4篇，SCI收录文章3篇，其中包括国际光学与光电子学领域顶尖学术期刊Optics Express 1篇，IEEE Photonics Journal 1篇以及Applied Physics B 1篇。培养博士与硕士研究生4人。