High power ultra short pulse lasers based on fiber driven OPCPA Ultrashort laser pulses enable fundamental studies on small length and time scales. Additionally high pulse energies allows the access to new regimes of light matter interaction and the investigation of nanometer scale structures on attosecond time scales by XUV pulses produced via high harmonic generation (HHG). Unfortunately the XUV photon flux is typically very low. Hence high power and high repetition rate driving laser sources are required in order to improve the performance of current studies and to open the way for new exiting applications such as seeding of free electron lasers. Regrettably conventional (Ti:Sa) laser technology is limited in output power due to the thermo optical effects in the amplifier crystals. The objective of this thesis is the development of a new power scalable laser concept merging OPCPA technology with state of the art high power fiber lasers. Based on modeling of the optical parametric amplifier important requirements on the OPCPA pump are found which are adopted in choice and development of the pump laser later. Furthermore the geometry of the optical parametric amplifier is optimized for ultra broadband amplification. Gain narrowing and saturation effects are investigated in order to achieve high conversion efficiency. In addition parasitic nonlinear effects such as second harmonic generation of signal and idler wave are studied and configurations are found which effectively avoid these unwanted effects.