  In this letter, we demonstrate the first all-fiber all-normal dispersion
ytterbium-doped oscillator with nonlinear multimodal interference based
saturable absorber capable to generate ultrashort dissipative soliton pulses.
Additional to functioning as a saturable absorber, the use of multimode fiber
segments between single mode fibers also ensures the bandpass filtering via
multimode interference reimaging necessary to obtain dissipative soliton
mode-locking. The oscillator generates dissipative soliton pulses at 1030 nm
with 5.8 mW average power, 5 ps duration and 44.25 MHz repetition rate. Pulses
are dechirped to 276 fs via an external grating compressor. All-fiber cavity
design ensures high stability and $\sim$70 dB sideband suppression is measured
in RF spectrum. Numerical simulations are performed to investigate cavity
dynamics and obtained results well-matched with experimental observations. The
proposed cavity presents an alternative approach to achieve all-fiber
dissipative soliton mode-locking with a simple and low-cost design.
