A BOTDA
system based on pulse coding and coherent detection comprises a narrow linewidth
laser device (10), a first polarization-maintaining coupler (11), a second polarization-maintaining coupler (12), a
microwave signal source (17), testing optical fibers (18), an
optical circulator (19), a 3dB coupler (20), a balance photoelectric
detector (21), a scrambler (16), a
spectrum analyzer (22) and a
digital signal processing unit (23), wherein
continuous light emitted by the arrow linewidth
laser device (10) is divided into two channels of
continuous light, namely, a first channel of the
continuous light and a second channel of the continuous light, through the first polarization-maintaining coupler (11); and the
system further comprises a
frequency shifter (9), a first electrooptical modulator (13), a pulse
signal source (14) and a second electrooptical modulator (15). The
system adopts a pulse coding technology and a coherent detection method, so that the
signal to
noise ratio of the BOTDA and the measurement accuracy can be improved, the sensing distance is increased, and the system has the function of
breakpoint detection.