A single-frequency narrow-linewidth fiber laser is presented,which is based on polarization maintaining(PM) fiber saturable absorber and fiber Bragg grating Fabry-Perot(FBG F-P) etalon.The high-gain Er3+ doped fiber was used as the gain medium,the traveling-wave cavity was selected to eliminate the spatial hole burning effect,and the FBG FP etalon was utilized to select longitudinal laser modes,so the single-frequency operation was achieved.A segment of Er3+-doped PM fiber acts as the saturabel ...