In this work, we numerically show that a continuum of light, generated by a femtosecond laser and a microstrured fiber (MF) can be used as tunable source for STED microscopy. The envisaged setup is composed by a microscope on which such a continuum is inserted. The spectral excitation and STED bands selection is performed by a monochromator based on an acousto-optic tunable filter (AOTF). Pulse temporal shapes fluctuations and intensity fluctuations effects are investigated. Those fluctuations are consistent with the experimental measurements. Temporal variations have little influence on the STED efficiency, whereas intensity fluctuations have much more effects.