The technique of Brillouin scattering distributed optical fiber sensing has been presented. Optical heterodyne detection was used to detect the weak Brillouin back scattering signal based on single longitudinal mode distributed feedback (DFB) laser and electric optical modulation technique. The scattering signal was amplified effectively by improving the filter and erbium doped fiber amplifier (EDFA). The 11 GHz radio-frequency (RF) signal of Brillouin back scattering is gathered and averaged. The experimental procedures and results are presented. The results show that the peak power of Brillouin back scattering at 11 GHz can reach 50 mV, and the intensity noise of light source induced the system's signal to noise ratio (SNR) decreased greatly, which reduced the difficulty of signal process in demodulation system. The experimental results confirm that the configuration is feasible.