In order to achieve even higher power levels in ytterbium-based fiber systems. all factors of the fiber must be considered. These can be achieved only via optimization of all the ytterbium fiber parameters, ranging from the core background losses to the geometrical properties, in order to reduce the splice losses within the cavity. Power scaling also requires optimization of matching passive fibers within the optical cavity. The optimization of the ytterbium-doped glass itself through host glass modification of various dopants also plays a large part in reducing the background loss of the glass, improvements in slope efficiency of the fiber, and improved photodarkening performance, all of which contribute to increased power levels in 1 µm systems.