  We have demonstrated a mode-locked Mamyshev oscillator based on a
single-mode-fibre configuration with low threshould. The influences of spectral
filters and the pump power on the output laser characteristics have been
investigated. In the case with spectral-filter central wavelength far away from
the peak of gain spectrum, the laser pulses have deviated slightly from
similariton evolution with gain-shaping under high pump power. Moreover,
self-starting mode-locking operation has been realized when the pump power was
only 520 mW, which might benefit from the appropriate polarization conditions
and small spectral filter separation. The laser can generate 1.89-nJ
ultra-short pulses with 20-dB spectral width of 54.6 nm. The pulse duration can
be compressed externally to 64.69 fs with the peak power of 21.3 kW.
