【作者】 李超；

【导师】 李桂芳；

【作者基本信息】 天津大学 ， 光学工程， 2017， 硕士

【摘要】 随着互联网时代的到来,人们对于网络容量的需求出现了爆炸式的增长。作为互联网的基石,现有的光纤通信系统正承受着越来越大的压力。受单模光纤的空间维度所限,在可预见的未来,单模光纤通信系统的传输容量将会快速逼近其香农极限。而少模光纤的出现则将是一种解决未来光通信系统容量危机的有效办法,但由于少模光通信器件的不成熟,少模光纤通信系统距离走向实际应用还尚需时日。然而,作为少模光纤传输系统的重要过渡阶段,准单模传输系统利用少模光纤传输单个模式,充分发挥了少模光纤大模场面积特性以及较高的非线性容限的优势,可大幅降低非线性损伤对传输信号的影响,提升系统的传输容量。本文正是围绕准单模传输这一中心目标,对于长跨距、长距离的准单模传输系统进行了深入的研究。主要的工作内容包括以下几个方面:(1)理论研究了模式正交性的原理,对于少模光纤中模式耦合的产生机制进行了研究和分析,并建立了光纤链路的数学模型,理论证明了利用自适应算法可以在数字域对模式耦合的损伤进行补偿。(2)分析和研究了模式群延迟的测量技术原理,搭建了实际的测试系统,对于少模光纤中的模式群延迟进行了测量,为准单模传输系统中DSP算法抽头数量的确定奠定了基础。(3)分析了相干光检测技术原理,开发了一整套的数字信号处理算法,用于PM-QPSK准单模传输系统中的信号解调和数据恢复,尤其是多径干扰补偿算法的使用,有效地弥补了准单模传输系统中模式耦合所引起的损伤。(4)开展了长距离、长跨距的准单模传输系统研究,分别进行了纯EDFA放大的准单模传输实验、Raman辅助EDFA放大的准单模传输实验以及长距离的双向准单模传输实验。在大抽头的CMA算法的帮助下,有效地补偿了少模光纤中由多径干扰所产生的损伤,分别实现了2500km、2100km和2200km的传输距离。更多还原

【Abstract】 With the advent of the era of Internet,the need of the network capacity around the world is in the form of explosive growth.As the cornerstone of the Internet,the optical fiber communication is facing increasing pressure.By the limit of the single-mode fiber’s spatial dimension,the transmission capacity of single-mode fiber will be approaching the Shannon limit in the foreseeable future.However,the crisis of future network capacity will be solved effectively due to the emergence of few-mode fiber.However,due to the immaturity of few-mode optical components,the practical application of few-mode fiber transmission system still need a long time.But,as an intermediate step towards the adoption of FMF transmissions,quasi-single-mode use the FMFs instead of large effective-area single-mode fibers.One can launch signals in the fundamental mode,for the large-effective-area nature of the LP₀₁mode in FMFs is able to considerably reduce the fiber nonlinearity and extend the transmission distance.This paper further study the long-span and long-haul quasi-single-mode transmission links.The main work will be arranged as follows:（1）We theoretically study that modes conducted in a fiber are orthonormal.The generation mechanism of mode coupling in the FMF is also studied and analyzed.Meanwhile,we establish the mathematical model of few-mode fiber link.And we have verified that the adaptive algorithm could be theoretically used to compensate the signal penalty resulting from mode coupling.（2）We analyses the basic principle of mode group delay measurement technology and set up practical system to measure mode group delay in the few-mode fiber,which is helpful to determine the number of taps in DSP algorithms.（3）We analyses the basic principle of coherent optical detection technology and develop a set of digital signal processing algorithms to demodulate signal in PM-QPSK quasi-single-mode transmission link.Based on multipath interference compensation algorithm,multipath interference penalty caused by mode coupling is effectively compensated in quasi-single-mode system.（4）We have demonstrated long-span and long-haul quasi-single-mode transmission experiments with EDFA amplification only or hybrid Raman-EDFA amplification.Moreover,we experimentally study long-haul bi-directional quasi-single-mode transmission.With multipath interference penalty compensation using the CMA algorithm with large number of taps,transmission distance of 2500 km,2100 km and 2200 km is realized,respectively.更多还原