We report a high-power, all-fiber Tm-doped laser system operating at 1908 nm, based on a master-oscillator power amplifier (MOPA) configuration. The oscillator utilizes two polarization-maintaining (PM) fiber Bragg gratings (FBGs) with orthogonal principal axes to achieve single-polarization output. The system generates a linearly polarized output power of 12.6 W, with a slope efficiency of 40.6%. The power is subsequently scaled to 207.6 W through a primary amplifier, which uses large mode area (LMA) fiber while maintaining single-mode operation. The amplifier achieves a beam quality factor (M²) of 1.36 and a polarization extinction ratio (PER) exceeding 18.3 dB.