We propose a novel framework for the solution of a general fiber Raman amplifier problem by use of a closed integral form of a Raman equation. Treating the given problem as an adiabatic system and taking the Raman process as the perturbation parameter, we can seek the solution along the iteration axis rather than the fiber propagation axis, permitting an orders-of-magnitude increase for the product of convergence speed and spatial resolution in the numerical assessment. (C) 2005 Optical Society of America.