Narrow-linewidth, wavelength tunable fiber lasers operating in the 1550-nm band have important applications in high-capacity communication systems, especially in wavelength-division-multiplexing (WDM). Such lasers will also have applications in optical sensors, high-resolution spectroscopy and photonics true-time-delay beamforming systems". In this paper, we report a wavelength tunable narrow linewidth single-wavelength Erbium-Ytterbium co-doped linear-cavity fiber laser using a chirped fiber Bragg grating combined with a novel switchable fiber Bragg grating (FBG) array. In this configuration, the chirped fiber Bragg grating acts as a partial-reflecting mirror and the switchable FBG array acts as the full-reflecting mirror and wavelength selector. The switchable FBG array consists of a 1x3 optical switch and three parallel discrete FBGs. The reflection wavelengths of each discrete FBG can be continuously tuned in a range of over 15 nm by stretching (7 nm) and compressing (8 nm) the FBG. Therefore a fiber linear-cavity laser with a very large wavelength tuning range can be successfully demonstrated. In our experiment, the wavelength tuning range of the fiber linear laser is 30 nm, from 1535 nm to 1565 nm. Within this tuning range, the total output power is about 6 dBm, the 3-dB linewidth is 0.01 nm, and the side mode suppression ratio is more than 30 dB.