RMS width of pulses in nonlinear dispersive fibers

An approximate analytical expression for the root means square (RMS) width of pulses propagating in nonlinear, dispersive fibers is derived. This result is useful for predicting how far a pulse can travel before it suffers significant distortion due to the combined influence of the nonlinearity of the refractive index and the dispersive properties of the fiber. This theory applies to pulses operating near the zero-dispersion wavelength where dispersion alone has a negligible influence, but where the combined influence of nonlinear self-phase modulation and dispersion can produce a significant effect.>