A BOTDA system that combined optical pulse coding techniques and coherent detection includes a narrow linewidth laser, two polarization-maintaining couplers, microwave generator, two electro-optic modulators (EOMs), fiber under test, an optical circulator, a 3 dB coupler, a polarization scrambler, a pulse generator, a balance photodetector, an electrical spectrum analyzer, digital signal processing unit and a frequency shifter. The optical pulse coding techniques and coherent detection are simultaneously used in the invented system, which can be enhance the signal-to-noise ration (SNR), the measuring accuracy and the sensing distance of BOTDA. Moreover, the proposed system has the capacity of break interrogation.
BOTDA system that combined optical pulse coding techniques and coherent detection