The optical network of a Brillouin optical time domain amplifier(BOTDA) system is proposed,in which only one laser source is used and the frequency scan range is decreased from the high frequency microwave(about 11 GHz) to the intermediate wave(MHz) without any frequency-shift locking device for cost saving.The experiment system was set up with the sensing fiber in the temperature controller,and the temperature-dependent Brillouin scattering signal was achieved.It is deduced that the Brillouin s...