Compact,　high-energy　ultrashort　pulsed　fiber　lasers　in　the　2.8　μm　wavelength　have　attracted　extensive　interest　in　many　scientific　and　industrial　applications.　Here,　we　demonstrated　the　generation　of　μJ-level　ultrashort　pulses　from　a　quasi-all-fiberized　Er:ZBLAN　amplifier　employing　a　2.8-μm　frequency-shifted　soliton　as　a　seed　laser.　With　backward　pumping,　the　pulse　energy　was　enhanced　to　0.282　μJ　when　the　average　output　power　was　amplified　to　1.023　W.　Mechanisms　for　the　generation　and　amplification　of　ultrashort　pulses　were　theoretically　revealed　by　numerical　simulation,　and　further　cascaded　indium　fluoride　(InF3)　fiber　to　obtain　a　4.26-μm　redshift　soliton　numerically.　This　compact　fiber　amplification　system　consisting　of　frequency-shifted-based　seed　pulses　and　fluoride　fiber　amplifiers　will　be　of　practical　interest　in　applications.　©　Published　under　licence　by　IOP　Publishing　Ltd.