A home-made fiber comb is developed based on the technology of Erbium-doped fiber femtosecond laser. The system configuration, working process and performance parameters of this comb are described in detail. A supercontinuum more than one octave is obtained after power amplification, dispersion optimization and spectrum spreading in highly nonlinear fibers. The carrier-envelope offset frequency (fo) is extracted by means of a linear f-2f interferometer and locked to a Rubidium atomic clock. The observed signal-to-noise ratio of fo is 35 dB and steady operation with locking time more than 12 h is demonstrated.