We　demonstrated　an　all-fiber　single-frequency　DBR　master　oscillator　and　power　amplifier　at　1992.6　nm.　The　maximum　output　power　of　the　fiber　amplifier　was　100　W　with　a　slope　efficiency　of　53%　and　the　optical　signal-to-noise　ratio　was　about　50dB.　The　linewidth　was　less　than　66　kHz　and　the　beam　quality　factor　M-2　was　1.22　at　the　maximum　output　power.　The　RINs　of　the　seed　and　the　power　amplifier　were　measured　to　be　-120　dB/Hz　and　-102　dB/Hz　at　the　relaxation　oscillation　frequency,　respectively.