In　this　work,　we　demonstrate　numerically　and　experimentally　an　all-fiber-integrated　gain-managed　nonlinear　(GMN)　amplification　system.　The　seed　is　a　nonlinear　amplifying　loop　mirror　(NALM)　mode-locked　Yb-doped　fiber　laser　with　a　pulse　duration　of　8.7　ps.　By　employing　a　chirped　fiber　Bragg　grating　(CFBG)　or　a　bandpass　filter　(BPF),　the　pulse　duration　of　seed　is　reduced　to　similar　to　1　ps.　The　pulses　are　then　injected　into　the　Yb-doped　fiber　amplifier　for　GMN　evolution.　Subsequently,　hollow-core　photonic　bandgap　(HC-PBG)　fibers　are　employed　for　dispersion　compensation　on　the　amplified　pulse.　In　the　BPF-filtered　configuration,　the　entire　system　accumulates　lower　higher-order　dispersion　and　is　capable　of　delivering　femtosecond　pulses　with　a　pulse　energy　of　163　nJ,　a　pulse　duration　of　45　fs,　and　a　peak　power　of　3.6　MW,　all　while　maintaining　a　highly　favorable　beam　quality　factor　(M-2)　of　1.05.　Compared　to　previously　reported　GMN　amplification　systems,　our　entire　system,　which　eliminates　any　sections　of　free-space　optics,　is　highly　attractive　due　to　its　ability　to　enhance　stability　and　compactness,　reduce　maintenance　demands　and　lower　costs.　We　believe　this　compact　femtosecond　fiber　laser　system,　with　its　ultrashort　pulse　duration　and　high　peak　power,　holds　potential　for　applications　in　scientific　research　and　precision　manufacturing.