【作者】 王晶；

【导师】 郑荣儿；

【作者基本信息】 中国海洋大学 ， 海洋信息探测与处理， 2008， 博士

【摘要】 由于光子晶体光纤新颖、灵活的特性突破了传统光纤光学的局限,大大拓展了光子晶体光纤的应用范围,并为克服传统光纤发展中的一些技术障碍提供了可能的解决途径。如利用光子晶体光纤可变的色散特性和强非线性效应,易实现孤子传输;又如充分发挥光子晶体光纤的弯曲损耗小、可传送大功率能量等优势,更适用于深海通信。如何实现长距离大容量的信息传输正是目前深海通信、深海探测等领域急需解决问题。本论文设计并数值模拟了光子晶体光纤中40Gbit/s孤子传输系统,为实现超长距离、超大容量新型通信系统提供理论支撑,以满足未来深海探测、深海通信系统的升级、换代的需求。论文综述了海洋的各种通信方式,包括无线声波通信、电通信、光孤子通信,特别是光子晶体光纤在孤子通信中的应用研究进展。指出未来适用于深海探测、深海通信的最佳方式之一就是采用新型光子晶体光纤为传输媒介、以光孤子为载体的光纤孤子通信系统。利用分步傅立叶方法数值计算了广义非线性薛定谔方程,从孤子脉冲传输和啁啾演变两个方面分析了40Gbit/s孤子系统的传输性能,及其各种效应对系统的影响;利用分步傅立叶方法数值计算了广义耦合非线性薛定谔方程,计算了飞秒孤子俘获现象,分析了光子晶体光纤中偏振复用孤子系统传输的可能性。本论文创新性工作如下:1)基于光与光纤介质相互作用机理,创建了啁啾研究方法。在光子晶体光纤中,从啁啾入手,推导了孤子形成的条件;针对飞秒孤子传输,推导了三阶色散产生的啁啾;并数值计算了群速度色散、自相位调制、三阶色散、自陡峭、脉冲内拉曼散射等效应产生的总啁啾;通过啁啾演变揭示了孤子传输时各种效应的作用及其相互作用的机理。并且,推导了偏振复用孤子系统中交叉相位调制效应产生的啁啾,分析了偏振模色散和交叉相位调制效应的相互作用所致啁啾演变的特性,进而解释偏振复用孤子的传输特性。2)利用分布傅立叶变化法,采用Matlab语言,编写了光子晶体光纤中单脉冲传输、系统中128bit脉冲序列的最大传输距离和眼图、在线同步调制和滑频滤波器补偿系统的程序。3)对光子晶体光纤中飞秒孤子传输的特性进行研究,获得了设计光子晶体光纤中孤子通信系统的有价值的数值解法。计算了理想孤子的传输的条件;数值分析了在传输中高阶色散效应、自陡峭效应、脉冲内拉曼散射效应、初始啁啾对孤子传输的影响:模拟了各种效应同时作用孤子的真实传输状态。并且,通过对光子晶体光纤中孤子脉冲传输的数值计算,发现了光子晶体光纤能够压缩脉冲,而且可获得压缩比较高、底座较小的窄脉冲。4)数值计算模拟了光子晶体光纤中40Gbit/s孤子传输系统,利用误码率和眼图对系统传输性能进行了评价。重点分析了系统传输最大距离和眼图在随偏振模色散的作用、群速度色散作用和脉冲占空比的变化;根据各种效应所致啁啾,为了优化系统性能,提出了两种系统的补偿方法,即利用同步调制和滑频滤波的方法对系统进行补偿,补偿效果非常明显。5)根据耦合的广义非线性薛定谔方程,利用分步傅里叶方法,研究了高阶非线性和高阶色散对孤子俘获的作用效果及其域值的影响。发现由于PCF具有较高的模式双折射度,飞秒量级的初始孤子脉冲可实现孤子俘获,分析了光子晶体光纤中实现偏振复用孤子系统的可能性。更多还原

【Abstract】 The photonic crystal fiber (PCF), as a recent version of fibers with many novel characteristics, has overcome the optical limitations of the traditional fiber and led to the widening of its applications. It also provides a possible solution to some technical obstacles in the development of traditional fiber. For example, the soliton transmission could be achieved easily, using the changeable dispersion and large nonlinear effects of the photonic crystal fiber. And with the small bending loss and the capability of the high-power transmission, the PCF could be helpful for some special application area, like deep sea communications. How to achieve the long-distance and large-capacity communications with great speed has been one of the key problems in the deep-sea communications and information transmission of deep-sea exploration. In the thesis, numerical simulation of the 40 Gbit/s soliton transmission system in the PCF was investigated, with the hope of giving some possible theoretical solutions for development of ultra-long-distance communication and large-capacity communication system, hence to satisfy the urgently demands for the upgrading of the communication system in the deep-sea exploration and deep-sea communications.The thesis begins with a detailed review of the relevant developments for the ocean communications, including underwater acoustic communication, underwater communication cable and optical soliton communication, with the focus on the status, advantages and development prospects of the optical soliton communication in the PCF. It has been suggested that the system with newly developed PCF as the transmission medium and the optical soliton as the carrier could be one of the best ways for future deep-sea communications. In the thesis, the nonlinear Schr(o|¨)dinger equation has been used for the analysis of 40Gbit/s soliton communication system using the split-step Fourier method. The system performance is numerical simulated based on the soliton transmission and chirps with the influence resulted from various effects. The coupled nonlinear Schr(o|¨)dinger equations for the femtosecond soliton self-trapping is numerical calculated by the split-step Fourier method. The possibility of the polarization multiplexing soliton communications system in PCF has also been analyzed. The author’s main contributions are concluded as following.1) Based on the interaction mechinese between light and the fiber, the method of the chirp research has been well established. With this method, the conditions for soliton forming in the PCF have been derived. It is found that three-order chromatic dispersion produces chirp in the femtosecond soliton transmission. The resultant total chip has been numerically calculated with the consideration of the joint effects from the group velocity dispersion (GVD), the self-phase modulation(SPM), the third-order dispersion(TOD), the self steepening (SS) and the intrapulse stimulated Raman scattering (ISRS). From the evolution of the chirp, we explain the physical mechanism of those effects and how each one acts on the soliton transmiting. We also derive the chirp produced by the cross-phases modulation effect and analyze the characteristic of the chirp evolution. As a result of this analysis, the property of the polarized multiplexing soliton transmission is opened out.2) Based on split-step Fourier method, a set of programs have been made for the numerical simulations of single pulse transmission in the PCF, the maximum transmission distance and system eye pattern of the 128bit pulse array, the on-line synchronal modulation and the sliding frequency filter compensations system.3) The transmission characteristics of the single soliton in the PCF have been studied. The obtained results have offered a valuable simulation for the design of the soliton transmission system in the PCF. In this thesis, the numerical calculations have been made for the transmission conditions of the ideal soliton, and the analysis of the effect resulted from the TOD, SS, ISRS and the initial chirp in the soliton transmission. The soliton actual transmission has been simulated with various effects active at the same time. With the numerical calculation of the pulse transmission in the PCF, it has been shown that the pulses could be compressed, and a narrow pulse with the high compression ratio and the small substrate base could be achieved in PCF.4) The 40Gbit/s soliton transmissions system in the PCF has been numerical simulated. The property of the system has been evaluated using bit error ratio and eye pattern. The special attention has been paid to the varying of maximum transmission distance and the eye pattern with PMD, GVD and duty cycle in the system. Based on the analysis of the chirps produced by various effects, we propose the two compensation methods to optimize the property of the system. They are on-line synchronal modulation and the sliding frequency filter, it has shown that both of them worked very well.5) Based on the coupling nonlinear Schr(o|¨)dinger equation, the soliton self-trapping and its generation threshold have been investigated using the split-step Fourier method, at the presence of the high-order nonlinear and the high-order dispersion. It has been found that the initial femtosecond soliton pulse could be trapped due to the higher mode birefringence of the PCF. The possibility of forming a polarized multiplexing soliton system in PCF has also been discussed.更多还原