Abstract
This paper studies the perturbation of the improved version of the nonlinear Schrodinger's equation that governs the propagation of solitons through nonlinear optical fibers. The semi-inverse variational principle is employed in order to obtain an analytical soliton solution in presence of the perturbation terms. There are three types of nonlinearity that will be studied. They are Kerr law, power law and the log law. The constraint conditions will naturally fall out in order for the soliton solutions to exist. The numerical simulations supplement the analytical results for each of the three laws of nonlinearity.