Of great interest in the use of Nd:YAG lasers is the possibility of transporting the beam inside an optical fiber. Pointed out in this work is the lower degradation of the beam quality using an optical fiber rather than using mirrors. The influence of the nature of the fiber (graded- and step-index fiber) on the focal point diameter, the position, etc., is compared. From this is demonstrated the interest of a graded-index fiber in materials processing such as cutting or welding and, in the case of laser cladding, the interest of a step-index fiber. It is concluded that materials processing applications can be successful using the two fibers according to the results needed.