We designed an all-normal dispersion ytterbium rod-type fiber laser oscillator delivering picosecond pulses which are continuously tunable both in central wavelength and pulse duration. This system delivers self-mode-locked pulses with an average power up to 25 W. At a repetition rate of 78 MHz, it yields picosecond laser pulses, of which the central wavelength and pulse duration can be tuned between 1010 nm - 1060 nm and 4.5 ps - 1.8 ps, respectively. The tunability is obtained by adjusting the position and the width of a slit which acts as a spectral bandwidth filter, placed close to the center of a 4f-folded zero dispersion line inserted in the laser cavity. This oscillator delivers nearly Fourier limited pulses with at most a 1.2 time-bandwidth product. A numerical model accounts well for the behavior of this all-normal dispersion fiber oscillator.

25 W self-modelocked fiber laser delivers picoseconds pulses at 78 MHz. The spectral width and central frequency of almost Fourier transform pulses are tunable between 0.38nm to 2.2nm and 1010nm to 1060nm, respectively.