Study On Propagation Properties Of Super-Gaussian Pulse In Optical Fibers

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.