Abstract

We obtained, by using the Painleve method, the bright solitary wave solution to an extended nonlinear Schrodinger equation, which models the propagation of ultrashort pulses, and found that a quadruple clad fiber is needed to propagate this solitary wave. The intensity of this solitary wave depends on the ratio of the third-order derivative of the propagation constant (β₃) and various higher order nonlinear (shock) terms coefficients. Since the higher order nonlinear coefficients are positive in optical fibers, we conclude that a negative β₃ is needed for this solitary wave and only a quadruple clad fiber is possible. And in addition, we required the wavelength to be >1.45 μm. This is in contrast to the soliton in the nonlinear Schrödinger equation, where a negative β₂, (group velocity dispersion) is needed. We also used a Gaussian approximation to evaluate the higher order nonlinear coefficients. The calculation indicated that these coefficients can be comparable to the other nonlinear terms (e.g., self phase modulation) when the pulse width is as short as 10 fs. These results may affect very high data rate systems.

© 1992 Optical Society of America