A novel operation scheme of a Brillouin/erbium fiber laser (BEFL) whose cavity consists of two metal-coated fiber planar mirrors (FPMs) and a Sagnac reflector is presented. Optical comb generation of both 10 and 20 GHz spacings is demonstrated by discrimination of the even order Stokes waves and the odd order Stokes waves. Theoretical analysis based on the reflection properties of the Sagnac reflector yields a good description of the multi-wavelength BEFL characteristics. (C) 2002 Elsevier Science B.V. All rights reserved.