Passively mode-locked fiber laser systems are emerging as attractive sources of powerful femtosecond pulses when the scientific impact and technological applications of ultrafast lasers are broadening rapidly. The aim of the present project is to help initiate a research effort in collaboration with other European scientists to develop ultrafast fiber laser technology for applications in accelerator-based light sources.Fiber lasers producing femtosecond pulses are emerging as extremely versatile and powerful tools for accelerator-based light sources, such as the Euro X-FEL in Germany, the Fermi@Elettra in Italy or the 4GLS in the UK. Despite notable improvements, there is little understanding of the noise properties of high-energy femtosecond fiber laser sources. Low noise is extremely important in various scientific and technological platforms, including accelerator applications.In the first phase of this project, we will characterize the amplitude and phase noise of Er- and Yb-doped fiber lasers operating in all of the commonly used regimes of mode-locking. The goal will be to identify for the first time the optimum mode of operation of a fiber laser to minimize noise. In addition, we will characterize residual noise imparted during amplification of femto second pulses in fiber amplifiers.The second phase is a development effort seeking maximal use of the know-how generated from the first phase. Here, the goal is to construct a femtosecond Yb-fiber laser for electron beam diagnostics using electro-optic techniques.