Single-frequency distributed Bragg reflector(DBR) fiber lasers were systematically investigated with rare-earth-doped silica fibers. The commercial Nd3+, Yb3+, Er3+/Yb3+ and Tm3+-doped silica fibers were applied in this demonstration to achieve the monolithic all-silica glass fiber lasers operating on single longitudinal mode. In the experiment, single-frequency operation was characterized, linewidth of tens of kilohertz was obtained (especially for the Er3+/Yb3+ co-doped fiber laser, the linewidth was narrow to 7 kHz) and the measured relative intensity noise approached the shot noise limit. The result confirms that commercial rare-earth-doped silica fiber can be an efficient gain medium to achieve single-frequency fiber laser with the wavelength range from 930 nm to 2 ?滋m, which can be further commercialized for a wide range of applications.