A passively mode-locked fiber ring laser with a small segment of Er3+-doped fiber as gain medium, pumped by stable 976 nm laser diode (LD) and mode-locked by the nonlinear polarization rotation (NPR) technique, was successfully achieved. When the laser was pumped at 57 mW, stable mode-locked pulses centered at 1544.0 nm with 40.8 nm spectral bandwidth and 78 fs pulse width were obtained at the repetition rate of 11.18 MHz by modulating the wavelength-independent all-fiber on-line polarization controller. The output power of the laser was 5.4 mW, the pulse energy was about 0.5 nJ and the peak power was 6200 W.