High power lasers play an important role in atomic physics, where laser cooling is required. One possibility to achieve high laser powers with a single-mode diode laser is to combine them with a tapered amplifier (TA). This thesis deals with the design and construction of a fiber-coupled TA system which allows stable adjustment of the collimation lenses. Two different designs were tested, one simple and compact design which allows the position of the collimation lenses to be adjusted along the optical axis and one more complex design which allows the position of the collimation lenses to be adjusted in all three directions. It was found to be crucial for fiber coupling optimization that the position of the collimation lenses can be controlled in all three spatial degrees of freedom. With the latter design and TA diode, it was possible to achieve a single-mode fiber coupling efficiency of 50 percent and a total power of 800mW after the single-mode fiber for a seed beam power of 30mW. Furthermore, a robust and cost-effective stand-alone TA unit is proposed and a list with all necessary information to build up such a stand-alone unit is given.