Pulse shaping strategies in short pulse fiber amplifiers Ultrashort pulse lasers are an important tool in scientific and industrial applications. However many applications are demanding higher average powers from these ultrashort pulse sources. This can be achieved by combining direct diode pumping with novel gain media designs. In particular ultrashort pulse fiber lasers are now delivering average powers in the kW range. However the design of fiber lasers producing pulses with high peak powers is challenging due to the impact of nonlinear effects. To significantly reduce these detrimental effects in ultrashort pulse fiber amplifers the combination of chirped pulse amplification (CPA) and large mode area fibers is employed. Using these methods the pulse energy of fiber lasers has been steadily increasing for the past few years. Recently a fiber based CPA system has been demonstrated which produces pulse energies of around 1 mJ. However both the stretching and the enlargement of the mode area are limited and therefore the impact of nonlinearity is still noticed in systems employing such devices. The aim of this thesis is the analysis of CPA systems operated beyond the conventional nonlinear limit which corresponds to accumulated nonlinear phase shifts around 1 rad. This includes a detailed discussion of the influence of the nonlinear effect self phase modulation on the output pulse of CPA systems. An analytical model is presented. Emphasis is placed on the design of novel concepts to control the impact of self phase modulation. Pulse shaping is regarded as a powerful tool to accomplish this goal. Novel methods to control the impact of SPM are experimentally demonstrated. The design of these concepts is based on the theoretical findings. Both amplitude and phase shaping are studied. Model based phase shaping is implemented in a state of the art fiber CPA system. The influence of the polarization state is also highlighted. Additionally existing techniques and recent advances are put into context.