We　report　a　thin-film　optical　amplifier　integrated　on　a　fiber　facet　based　on　polymer-coated　distributed　feedback　(DFB)　microcavities,　which　are　fabricated　on　a　planar　substrate　and　then　transferred　onto　fiber　tips　by　means　of　a　flexible　transfer　technique.　The　amplified　light　directly　couples　into　the　fiber　and　is　detected　when　coupled　out　at　the　other　end　after　propagating　along　the　fiber　for　about　20　cm.　A　prominently　amplification　factor　of　about　4.33　at　578.57　nm　is　achieved　by　sending　supercontinuum　pulses　into　the　hundreds　of　micrometers＇　DFB　microcavities　along　the　normal　direction,　which　is　also　the　axis　direction　of　the　fiber.　The　random　distortions　of　grating　lines　generated　during　the　transfer　process　result　in　a　larger　amplification　spectral　range　and　a　less　strict　polarization　dependence　for　injected　light.　Benefitting　from　the　device　size　of　hundreds　of　micrometers　and　the　ease　of　integration,　polymer　amplifiers　based　on　DFB　microcavities　demonstrate　significant　application　potentials　in　optical　communication　systems　and　miniaturized　optical　devices.