We present a study of a gain-switched end-pumped Yb-doped-fiber laser. The test laser that was mainly used in order to verify the theoretical model consist of an 8.7 m long double clad active fiber with core and inner cladding diameter of 8 μm and 130 μm respectively, and absorption of 1.5 dB/m. An important part of the system is a control unit that switches on the pumping diodes at a desired repetition rate and switches off at the moment when the first spike of the transitional effect appears in order to suppress additional oscillations. A simple rate equation model accurately predicts the main pulse parameters. It describes the population dynamics of the photons and the laser levels, including the occupation by thermal effects. Further numerical simulations show that with adequate active fiber geometry, active ion doping and sufficient pumping power, much shorter pulses in range of 50 ns and peak power of several 100W can be achieved. Such a simple system with the potential addition of a one stage active fiber amplifier can be interesting for some applications in micro-processing like scribing of solar cells, micro processing, and thin film removal.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.