An all-fiber single-frequency distributed Bragg reflector (DBR) laser at 1944 nm was demonstrated using a 2 cm-long homemade Tm-doped yttrium aluminum garnet (YAG) crystal-derived silica fiber (TYDSF). The laser delivered stable single transverse and longitudinal mode operation with an output power of 226 mW, achieving a slope efficiency of 38.83%, an optical signal-to-noise ratio >81 dB, a pump threshold as low as 21 mW, and power fluctuations <0.27% over 10 hours. To the best of our knowledge, a beat-frequency technique based on a single-frequency Brillouin/Thulium fiber laser was employed to characterize the 2 μm-band laser linewidths for the first time, achieving a narrowed linewidth of 9.25 kHz via a passive optical feedback loop. These results underscore the laser’s potential as robust seed sources for medical surgery, atmospheric monitoring, and mid-infrared coherent communications.