A new conserved quantity for non-Kerr law optical solitons

This paper talks about a new conservation law in non-Kerr law media. This new integral of motion is used to provide an equation for the phase of the soliton. This law is also used to obtain the adiabatic variation of the soliton phase due to perturbation terms in a non-Kerr law media that includes the power law, parabolic law and the dual-power law.