In this work, we present a short- and long-term operation and environmentally-stable, all-polarizationmantained, Fabry-Pérot resonator, passively mode-locked fiber laser operating in an all-anomalousdispersion solitonic regime. Our results confirm that the highly stable operation of the laser oscillator is maintained after amplifying the laser output with a conventional EDFA. Such stability has been studied by a variety of measurements in the temporal and spectral -both optical and electrical- domains before and after amplification. Pulse durations of 540 fs, period-relative time jitters of 0.015%, and long-term uninterrumped operation with <1.8% variation of the individually photodetected pulse peak powers are obtained for the laser oscillator. After amplification, dispersion-induced pulse durations of 244 fs, period-relative time jitters of 0.019% and an average output power of 20mW are obtained, while maintaining the 100 dB signal-to-noise ratio (SNR) measured at 500 Hz offset from the fundamental harmonic frequency of the photodetected signal. We have also carried out a theoretical validation of the emission properties of our laser oscillator based on solutions of the Nonlinear Schröedinger Equation that take into account wavelength and z-position dependence of the active medium gain.