In this work, an analysis for a self-pulsing behavior within a large-mode-area Ytterbium-doped
fibre laser operated as a free running laser is presented. A set of equations that describes the
relaxation oscillations frequency by considering a cavity as well as the atomic rate equations
were obtained. In here, the behaviour of the self-pulsing is due to the un-pumped fibre section
that plays a key role for the saturate absorber. Analytical results depicts that instead of reaching a
continuous wave-based regime, the laser output will show pulses with an increasing repetition
rate due to the pump power is higher. It is in good agreement with the natural behaviour
observed within this fibre laser
