New types of solitary wave solutions for the higher order nonlinear Schrodinger equation

We present new types of solitary wave solutions for the higher order nonlin ear Schrodinger (HNLS) equation describing propagation of femtosecond light pulses in an optical fiber under certain parametric conditions. Unlike the reported solitary wave solutions of the HNLS equation, the novel ones can describe bright and dark solitary wave properties in the same expressions a nd their amplitude may approach nonzero when the time variable approaches i nfinity. In addition, such solutions cannot exist in the nonlinear Schrodin ger equation. Furthermore, we investigate the stability of these solitary w aves under some initial pertubations by employing the numerical simulation methods.