【作者】 甘桂蓉；

【导师】 罗开基；

【作者基本信息】 江西师范大学 ， 光学， 2008， 硕士

【摘要】 本文首先介绍了光纤通信技术的发展和现状及光脉冲在光纤的传输理论,然后对MNLS方程引入超高斯型脉冲的尝试解,并采用变分法,推导出一般情况、无微扰、小损耗微扰、高阶色散微扰、五阶非线性微扰、耦合相互作用微扰等六种不同情况下超高斯型脉冲各参数(振幅A、脉宽a、啁啾b、频率ω、中心位置ξ、相位φ)随传输距离z的演化方程组;在此基础上,讨论了各参数随传输距离z的演化特性,并且得到了无微扰、小损耗微扰、高阶色散微扰、五阶非线性及耦合相互作用微扰五种情况下的参数ω、ξ、a、b的解析解;重点讨论了无微扰、高阶色散微扰、五阶非线性微扰三种情况下,初始啁啾对脉宽的影响及高阶色散系数β和五阶非线性系数γ对脉宽的影响,作出了相应的曲线图形,并得到以下结论:(1)各种情况下,初始啁啾对光纤中传输的超高斯型脉冲均有影响:初始啁啾b0为负值时,初期脉冲有一窄化过程,且其绝对值越大,脉冲宽度的振荡越慢而振荡幅度越大.脉冲前后沿越锐,脉冲宽度的振荡越慢而振荡幅度越大.(2)除耦合相互作用外,各种情况下,振幅A和脉宽a满足绝热条件,频率ω、啁啾b和中心位置ξ间存在一约束关系式,脉宽a和啁啾b间也存在一约束关系式。(3)小损耗只对相位φ产生影响,它导致脉冲峰值功率的衰减;除对ξ无影响外,前后沿锐度m对其他脉冲参数有直接或间接的影响。(4)高阶色散、五阶非线性和耦合相互作用微扰均会激起啁啾;(5)高阶色散微扰和脉冲前后沿锐度对参数A、a、b、ω、ξ、φ均有影响。高阶色散使超高斯脉冲展宽。(6)五阶非线性微扰作用下,五阶非线性、初始啁啾和脉冲前后沿锐度对参数A、a、b、ω、φ均有影响,而五阶非线性对ξ没有影响。五阶非线性使超高斯脉冲压缩。五阶非线性和脉冲前后沿锐度对脉宽的影响可以部分平衡。(7)耦合相互作用微扰产生的啁啾与高阶色散微扰作用的情况相似,对振幅、脉宽、频率、中心位置、相位的演化规律都有直接的影响,而且破坏了超高斯型脉冲的绝热特性。更多还原

【Abstract】 In this paper, firstly the origin, development and current research of optical fiber communications are introduced briefly, then, based on the MNLS equation, the answers of super-Gaussian pulse are introduced. The variational method is used to deduce the evolution equations for the parameters [amplitude(A), frequency band width(a), chirp(b), frequency(ω), center position(ξ), phase(ф)] of super-Gaussian pulses in common situation, without perturbation, and situation of the small dielectric loss, the higher-order dispersion, the fifth-order nonlinearity and the influence of the couple-interaction. By these equations, the properties of the parameters are discussed when the distance Z changed and the answers to the evolution equations of the parameters (a,b,ω,ξ) are derived under in the situation of without perturbation. Then the perturbation to the width made by the small dielectric loss, the higher-order dispersion and the fifth-order nonlinearity are mainly discussed, and the curves of the frequency band width (a), the in the situation of without perturbation, the higher-order dispersion and the fifth-order nonlinearity are described. The conclusions are:(1)The effects of initial chirp exist in all cases while the super-Gaussian pulses transmitting in fibers:initial chirp b0 is negative, there is a narrow pulse in the initial process, and its absolute value is bigger, pulse width’s vibration is slower and the oscillation amplitude is greater. The sharper the degree of the pulse`s edge sharpness is, The slower the pulse width’s vibration is and the greater the oscillation amplitude is.(2) In all cases except the coupled interaction, pulse width frequency band width a and amplitude A satisfy the adiabatic condition, frequencyω, chirp b and central positionξsatisfy the constraint relation, and pulse width a and chirp b meet another relationship.(3) The small dielectric loss effects onф, it leads to the decrease of the power of the pulse;(4) All of the higher-order dispersion, the fifth-order nonlinearity and the couple interaction can bring about chirp wave;(5) The higher-order dispersion and the degree of the pulse`s edge sharpness have large effect on A、a、b、ω、ξ、φ,and the higher-order chromatic dispersion causes the super-Gaussian pulse widening(6)The fifth-order nonlinearity and the chirps and the degree of the pulse`s edge sharpness have effect on A、a、b、ω、φ,but the former has no effect onξ. The fifth-order nonlinearity causes the super-Gaussian pulse compression, and the influence of the fifth-order nonlinearity and the degree of the pulse`s edge sharpness on the pulse-width can counterbalances in part;(7) The chirp wave brought by the coupled interaction also has direct effect on Ap、ap、bp、ωp、ξp、φp,what’s more, it demolishes the adiabatic property.更多还原