[2] Hasegawa A. Optical Soliton，Fiber [M]. New York: Spring-Verlag, 1989

[5] Bondeson A, Lisak W, Anderson D. Soliton perturbations: a variational principle for the parameters [J]. Physica Script, 1979, 20: 479-485

[7] Anderson D. Variational approach to nonlinear pulse propagation in optical fibers [J]. Phys. Rev. A, 1983, 27(6):3135-3145.