Abstract: The present invention is a method and system for reducing contamination in the resulting plasma of a weld produced by a fiber laser. The invention establishes the fiber laser in an optimal configuration for applying a high density beam to a weld material that eliminates spectral interference. The beam is applied in a narrow bandwidth of 1064 nm+/?0.5 nm in one operative condition using an inert shielding gas, preferably argon, in a cross-flow or controlled environment around the welding region to prevent contamination of the plasma forming in the weld region. The method is optimized by determining and avoiding the emission spectrum for the fiber laser and the cover gas or gasses as well as any particular excitation spectra for the weld material. The system can utilize a single laser input, or can utilize multiple lasers joined by coupling means and utilizing a switch to select one or more of the fiber lasers.