In experiments with rare-earth-doped fibers impressively results have been demonstrated and shown that fiber lasers and amplifiers are an attractive and power scalable solid-state laser concept. With ytterbium-doped large-mode-area double-clad fibers, output powers approaching the kW-range with diffraction limited beam quality have been realized in the continuous regime. Also in the pulsed regime, even for femtosecond pulse duration average output powers in the range of 100 W have been demonstrated. Further power scaling is limited by the end facets damage, thermo-optical problems or nonlinear effects. To overcome these restrictions microstructured fibers can be used. This type of fibers has several new preferable features. In our contribution we will discuss the advantages of microstructured fibers to reduce nonlinear effects inside the fiber and the possibility to scale the output power of fiber lasers and amplifiers with excellent beam quality. We also show fiber based chirped pulse amplification system (CPA-System) with ultra short pulses, pulse energies of up to 100 μJ and high repetition rates.